I have checked everything and the oscillator absolutely refuses to work. All paper and filter capacitors have been replaced. No part of the oscillator coil is open. The resistors are good. I tried a few 6A7s and it still wont work. What to I look at next?
This is an AC/DC set. There's not that much there.
Thanks,
Dave
If all fails, walk away for a while and then come back and check carefully all the wiring around the osc circuit for correctness and good solder joints. Did you check C9 (probably a mica)or replace it. If not may try substituting another. Voltage checks on the stage may give a clue if any are off very much.
Radiodoc
***********
:Hello All,
: I have checked everything and the oscillator absolutely refuses to work. All paper and filter capacitors have been replaced. No part of the oscillator coil is open. The resistors are good. I tried a few 6A7s and it still wont work. What to I look at next?
: This is an AC/DC set. There's not that much there.
:
:Thanks,
:
:Dave
C9 is a 100 pf capacitor. I replaced it and it made absolutely no difference.
Dave
:Dave,
:
:If all fails, walk away for a while and then come back and check carefully all the wiring around the osc circuit for correctness and good solder joints. Did you check C9 (probably a mica)or replace it. If not may try substituting another. Voltage checks on the stage may give a clue if any are off very much.
:
:Radiodoc
:***********
:
:
::Hello All,
:: I have checked everything and the oscillator absolutely refuses to work. All paper and filter capacitors have been replaced. No part of the oscillator coil is open. The resistors are good. I tried a few 6A7s and it still wont work. What to I look at next?
:: This is an AC/DC set. There's not that much there.
::
::Thanks,
::
::Dave
B+ is 98 volts. Is that low? Shouldn't it be a little higher? I can't see any way to raise it. Filament voltage on the 6A7 is 5.3 volts.
Thanks,
Dave
:Radiodoc,
: C9 is a 100 pf capacitor. I replaced it and it made absolutely no difference.
:
:Dave
::Dave,
::
::If all fails, walk away for a while and then come back and check carefully all the wiring around the osc circuit for correctness and good solder joints. Did you check C9 (probably a mica)or replace it. If not may try substituting another. Voltage checks on the stage may give a clue if any are off very much.
::
::Radiodoc
::***********
::
::
:::Hello All,
::: I have checked everything and the oscillator absolutely refuses to work. All paper and filter capacitors have been replaced. No part of the oscillator coil is open. The resistors are good. I tried a few 6A7s and it still wont work. What to I look at next?
::: This is an AC/DC set. There's not that much there.
:::
:::Thanks,
:::
:::Dave
I took out the oscillator coil and checked every connection and all are good (Perfect), no opens. I checked and cleaned the band switch several times. I replaced C9 several times. When I connect 456 Kc to it from my RF signal generator, it receives that tone perfectly. It blasts!! But it wont take what's presented to it from the antenna terminals and convert that to 456 Kc. It absolutely refuses to do that under any circumstances.
I checked all the connections and they are perfectly perfectly perfect. The resistors are all the correct values. The solder connections have been re-done and they are nice and shiny.
I tried 3 different 6A7 tubes and none of them make any difference.
I checked to make sure that the tuning capacitor or trimmer have any shorts on the oscillator side and there are no shorts. When the set is on and I try to adjust the oscillator screw or short the rotor with the stator on the oscillator side it makes no difference at all. All it's doing is "TRFing". The person who owns this radio MUST have the radio working immediately. I must continue working on it until it works. What do I do next? How do I convert it to a TRF receiver?
Thanks,
Dave
:Radiodoc,
: B+ is 98 volts. Is that low? Shouldn't it be a little higher? I can't see any way to raise it. Filament voltage on the 6A7 is 5.3 volts.
:
:Thanks,
:
:Dave
::Radiodoc,
:: C9 is a 100 pf capacitor. I replaced it and it made absolutely no difference.
::
::Dave
:::Dave,
:::
:::If all fails, walk away for a while and then come back and check carefully all the wiring around the osc circuit for correctness and good solder joints. Did you check C9 (probably a mica)or replace it. If not may try substituting another. Voltage checks on the stage may give a clue if any are off very much.
:::
:::Radiodoc
:::***********
:::
:::
::::Hello All,
:::: I have checked everything and the oscillator absolutely refuses to work. All paper and filter capacitors have been replaced. No part of the oscillator coil is open. The resistors are good. I tried a few 6A7s and it still wont work. What to I look at next?
:::: This is an AC/DC set. There's not that much there.
::::
::::Thanks,
::::
::::Dave
Are the symptoms the same for both SW and BC?
marv
:Radiodoc,
: I took out the oscillator coil and checked every connection and all are good (Perfect), no opens. I checked and cleaned the band switch several times. I replaced C9 several times. When I connect 456 Kc to it from my RF signal generator, it receives that tone perfectly. It blasts!! But it wont take what's presented to it from the antenna terminals and convert that to 456 Kc. It absolutely refuses to do that under any circumstances.
: I checked all the connections and they are perfectly perfectly perfect. The resistors are all the correct values. The solder connections have been re-done and they are nice and shiny.
: I tried 3 different 6A7 tubes and none of them make any difference.
: I checked to make sure that the tuning capacitor or trimmer have any shorts on the oscillator side and there are no shorts. When the set is on and I try to adjust the oscillator screw or short the rotor with the stator on the oscillator side it makes no difference at all. All it's doing is "TRFing". The person who owns this radio MUST have the radio working immediately. I must continue working on it until it works. What do I do next? How do I convert it to a TRF receiver?
:
:Thanks,
:
:Dave
::Radiodoc,
:: B+ is 98 volts. Is that low? Shouldn't it be a little higher? I can't see any way to raise it. Filament voltage on the 6A7 is 5.3 volts.
::
::Thanks,
::
::Dave
:::Radiodoc,
::: C9 is a 100 pf capacitor. I replaced it and it made absolutely no difference.
:::
:::Dave
::::Dave,
::::
::::If all fails, walk away for a while and then come back and check carefully all the wiring around the osc circuit for correctness and good solder joints. Did you check C9 (probably a mica)or replace it. If not may try substituting another. Voltage checks on the stage may give a clue if any are off very much.
::::
::::Radiodoc
::::***********
::::
::::
:::::Hello All,
::::: I have checked everything and the oscillator absolutely refuses to work. All paper and filter capacitors have been replaced. No part of the oscillator coil is open. The resistors are good. I tried a few 6A7s and it still wont work. What to I look at next?
::::: This is an AC/DC set. There's not that much there.
:::::
:::::Thanks,
:::::
:::::Dave
Yes, exactly the same.
Thanks,
Dave
:Dave,
:Are the symptoms the same for both SW and BC?
:
:marv
:
::Radiodoc,
:: I took out the oscillator coil and checked every connection and all are good (Perfect), no opens. I checked and cleaned the band switch several times. I replaced C9 several times. When I connect 456 Kc to it from my RF signal generator, it receives that tone perfectly. It blasts!! But it wont take what's presented to it from the antenna terminals and convert that to 456 Kc. It absolutely refuses to do that under any circumstances.
:: I checked all the connections and they are perfectly perfectly perfect. The resistors are all the correct values. The solder connections have been re-done and they are nice and shiny.
:: I tried 3 different 6A7 tubes and none of them make any difference.
:: I checked to make sure that the tuning capacitor or trimmer have any shorts on the oscillator side and there are no shorts. When the set is on and I try to adjust the oscillator screw or short the rotor with the stator on the oscillator side it makes no difference at all. All it's doing is "TRFing". The person who owns this radio MUST have the radio working immediately. I must continue working on it until it works. What do I do next? How do I convert it to a TRF receiver?
::
::Thanks,
::
::Dave
:::Radiodoc,
::: B+ is 98 volts. Is that low? Shouldn't it be a little higher? I can't see any way to raise it. Filament voltage on the 6A7 is 5.3 volts.
:::
:::Thanks,
:::
:::Dave
::::Radiodoc,
:::: C9 is a 100 pf capacitor. I replaced it and it made absolutely no difference.
::::
::::Dave
:::::Dave,
:::::
:::::If all fails, walk away for a while and then come back and check carefully all the wiring around the osc circuit for correctness and good solder joints. Did you check C9 (probably a mica)or replace it. If not may try substituting another. Voltage checks on the stage may give a clue if any are off very much.
:::::
:::::Radiodoc
:::::***********
:::::
:::::
::::::Hello All,
:::::: I have checked everything and the oscillator absolutely refuses to work. All paper and filter capacitors have been replaced. No part of the oscillator coil is open. The resistors are good. I tried a few 6A7s and it still wont work. What to I look at next?
:::::: This is an AC/DC set. There's not that much there.
::::::
::::::Thanks,
::::::
::::::Dave
The 98 volts is probably ok. If all else failed and as a shot in the dark, I would reverse the coil leads on the non-tuned winding between B+ and the oscillator "plate" and see what happens.
Radiodoc
***************
:Radiodoc,
: I took out the oscillator coil and checked every connection and all are good (Perfect), no opens. I checked and cleaned the band switch several times. I replaced C9 several times. When I connect 456 Kc to it from my RF signal generator, it receives that tone perfectly. It blasts!! But it wont take what's presented to it from the antenna terminals and convert that to 456 Kc. It absolutely refuses to do that under any circumstances.
: I checked all the connections and they are perfectly perfectly perfect. The resistors are all the correct values. The solder connections have been re-done and they are nice and shiny.
: I tried 3 different 6A7 tubes and none of them make any difference.
: I checked to make sure that the tuning capacitor or trimmer have any shorts on the oscillator side and there are no shorts. When the set is on and I try to adjust the oscillator screw or short the rotor with the stator on the oscillator side it makes no difference at all. All it's doing is "TRFing". The person who owns this radio MUST have the radio working immediately. I must continue working on it until it works. What do I do next? How do I convert it to a TRF receiver?
:
:Thanks,
:
:Dave
::Radiodoc,
:: B+ is 98 volts. Is that low? Shouldn't it be a little higher? I can't see any way to raise it. Filament voltage on the 6A7 is 5.3 volts.
::
::Thanks,
::
::Dave
:::Radiodoc,
::: C9 is a 100 pf capacitor. I replaced it and it made absolutely no difference.
:::
:::Dave
::::Dave,
::::
::::If all fails, walk away for a while and then come back and check carefully all the wiring around the osc circuit for correctness and good solder joints. Did you check C9 (probably a mica)or replace it. If not may try substituting another. Voltage checks on the stage may give a clue if any are off very much.
::::
::::Radiodoc
::::***********
::::
::::
:::::Hello All,
::::: I have checked everything and the oscillator absolutely refuses to work. All paper and filter capacitors have been replaced. No part of the oscillator coil is open. The resistors are good. I tried a few 6A7s and it still wont work. What to I look at next?
::::: This is an AC/DC set. There's not that much there.
:::::
:::::Thanks,
:::::
:::::Dave
I think you mean the secondary of the "transformer" (oscillator coil). One wire now is connecting directly to B+ and the other to that "Plate" grid on the converter. OK I will attempt it and then let you know what happened.
Thanks,
:Dave,
:
:The 98 volts is probably ok. If all else failed and as a shot in the dark, I would reverse the coil leads on the non-tuned winding between B+ and the oscillator "plate" and see what happens.
:
:Radiodoc
:***************
:
::Radiodoc,
:: I took out the oscillator coil and checked every connection and all are good (Perfect), no opens. I checked and cleaned the band switch several times. I replaced C9 several times. When I connect 456 Kc to it from my RF signal generator, it receives that tone perfectly. It blasts!! But it wont take what's presented to it from the antenna terminals and convert that to 456 Kc. It absolutely refuses to do that under any circumstances.
:: I checked all the connections and they are perfectly perfectly perfect. The resistors are all the correct values. The solder connections have been re-done and they are nice and shiny.
:: I tried 3 different 6A7 tubes and none of them make any difference.
:: I checked to make sure that the tuning capacitor or trimmer have any shorts on the oscillator side and there are no shorts. When the set is on and I try to adjust the oscillator screw or short the rotor with the stator on the oscillator side it makes no difference at all. All it's doing is "TRFing". The person who owns this radio MUST have the radio working immediately. I must continue working on it until it works. What do I do next? How do I convert it to a TRF receiver?
::
::Thanks,
::
::Dave
:::Radiodoc,
::: B+ is 98 volts. Is that low? Shouldn't it be a little higher? I can't see any way to raise it. Filament voltage on the 6A7 is 5.3 volts.
:::
:::Thanks,
:::
:::Dave
::::Radiodoc,
:::: C9 is a 100 pf capacitor. I replaced it and it made absolutely no difference.
::::
::::Dave
:::::Dave,
:::::
:::::If all fails, walk away for a while and then come back and check carefully all the wiring around the osc circuit for correctness and good solder joints. Did you check C9 (probably a mica)or replace it. If not may try substituting another. Voltage checks on the stage may give a clue if any are off very much.
:::::
:::::Radiodoc
:::::***********
:::::
:::::
::::::Hello All,
:::::: I have checked everything and the oscillator absolutely refuses to work. All paper and filter capacitors have been replaced. No part of the oscillator coil is open. The resistors are good. I tried a few 6A7s and it still wont work. What to I look at next?
:::::: This is an AC/DC set. There's not that much there.
::::::
::::::Thanks,
::::::
::::::Dave
I just tried that and it makes absolutely no difference whatsoever.
What do I look at next?
Thanks,
:Dave,
:
:The 98 volts is probably ok. If all else failed and as a shot in the dark, I would reverse the coil leads on the non-tuned winding between B+ and the oscillator "plate" and see what happens.
:
:Radiodoc
:***************
:
::Radiodoc,
:: I took out the oscillator coil and checked every connection and all are good (Perfect), no opens. I checked and cleaned the band switch several times. I replaced C9 several times. When I connect 456 Kc to it from my RF signal generator, it receives that tone perfectly. It blasts!! But it wont take what's presented to it from the antenna terminals and convert that to 456 Kc. It absolutely refuses to do that under any circumstances.
:: I checked all the connections and they are perfectly perfectly perfect. The resistors are all the correct values. The solder connections have been re-done and they are nice and shiny.
:: I tried 3 different 6A7 tubes and none of them make any difference.
:: I checked to make sure that the tuning capacitor or trimmer have any shorts on the oscillator side and there are no shorts. When the set is on and I try to adjust the oscillator screw or short the rotor with the stator on the oscillator side it makes no difference at all. All it's doing is "TRFing". The person who owns this radio MUST have the radio working immediately. I must continue working on it until it works. What do I do next? How do I convert it to a TRF receiver?
::
::Thanks,
::
::Dave
:::Radiodoc,
::: B+ is 98 volts. Is that low? Shouldn't it be a little higher? I can't see any way to raise it. Filament voltage on the 6A7 is 5.3 volts.
:::
:::Thanks,
:::
:::Dave
::::Radiodoc,
:::: C9 is a 100 pf capacitor. I replaced it and it made absolutely no difference.
::::
::::Dave
:::::Dave,
:::::
:::::If all fails, walk away for a while and then come back and check carefully all the wiring around the osc circuit for correctness and good solder joints. Did you check C9 (probably a mica)or replace it. If not may try substituting another. Voltage checks on the stage may give a clue if any are off very much.
:::::
:::::Radiodoc
:::::***********
:::::
:::::
::::::Hello All,
:::::: I have checked everything and the oscillator absolutely refuses to work. All paper and filter capacitors have been replaced. No part of the oscillator coil is open. The resistors are good. I tried a few 6A7s and it still wont work. What to I look at next?
:::::: This is an AC/DC set. There's not that much there.
::::::
::::::Thanks,
::::::
::::::Dave
Be absolutely sure that neither caps at C3 location are shorted. The so called secondary (right side of
T-2)is a non resonant feedback or tickler winding, and probably just a few turns too. If you rewired this part of the radio, make sure the windings were not switched around. If connected wrong, the tickler would not resonate at the correct frequency with the tuning/trimmer caps C-3. In addition, a simple continuity test of each winding does not measure the inductance, hence a few shorted turns could have the primary tank circuit oscillating well above the required freq. If you have an oscilloscope, this can be verified. You might be able to feed modulated RF into the antenna circuit, and try frequencies above std BC to see if an IF frequency or birdie is detected. Is there a voltage across R-2, which would indicate the tube is drawing current and trying to oscillate?
marv
:Radiodoc,
: I just tried that and it makes absolutely no difference whatsoever.
: What do I look at next?
:
:Thanks,
:
::Dave,
::
::The 98 volts is probably ok. If all else failed and as a shot in the dark, I would reverse the coil leads on the non-tuned winding between B+ and the oscillator "plate" and see what happens.
::
::Radiodoc
::***************
::
:::Radiodoc,
::: I took out the oscillator coil and checked every connection and all are good (Perfect), no opens. I checked and cleaned the band switch several times. I replaced C9 several times. When I connect 456 Kc to it from my RF signal generator, it receives that tone perfectly. It blasts!! But it wont take what's presented to it from the antenna terminals and convert that to 456 Kc. It absolutely refuses to do that under any circumstances.
::: I checked all the connections and they are perfectly perfectly perfect. The resistors are all the correct values. The solder connections have been re-done and they are nice and shiny.
::: I tried 3 different 6A7 tubes and none of them make any difference.
::: I checked to make sure that the tuning capacitor or trimmer have any shorts on the oscillator side and there are no shorts. When the set is on and I try to adjust the oscillator screw or short the rotor with the stator on the oscillator side it makes no difference at all. All it's doing is "TRFing". The person who owns this radio MUST have the radio working immediately. I must continue working on it until it works. What do I do next? How do I convert it to a TRF receiver?
:::
:::Thanks,
:::
:::Dave
::::Radiodoc,
:::: B+ is 98 volts. Is that low? Shouldn't it be a little higher? I can't see any way to raise it. Filament voltage on the 6A7 is 5.3 volts.
::::
::::Thanks,
::::
::::Dave
:::::Radiodoc,
::::: C9 is a 100 pf capacitor. I replaced it and it made absolutely no difference.
:::::
:::::Dave
::::::Dave,
::::::
::::::If all fails, walk away for a while and then come back and check carefully all the wiring around the osc circuit for correctness and good solder joints. Did you check C9 (probably a mica)or replace it. If not may try substituting another. Voltage checks on the stage may give a clue if any are off very much.
::::::
::::::Radiodoc
::::::***********
::::::
::::::
:::::::Hello All,
::::::: I have checked everything and the oscillator absolutely refuses to work. All paper and filter capacitors have been replaced. No part of the oscillator coil is open. The resistors are good. I tried a few 6A7s and it still wont work. What to I look at next?
::::::: This is an AC/DC set. There's not that much there.
:::::::
:::::::Thanks,
:::::::
:::::::Dave
There's no short at C3. I disconnected the wire from the band switch and nothing is shorted. The tuning capacitor has no shorts in either section and the trimmers don't have shorts either.
I will check for a voltage across R2 and let you know what I've found.
Thanks,
Dave
:Dave,
:Be absolutely sure that neither caps at C3 location are shorted. The so called secondary (right side of
:T-2)is a non resonant feedback or tickler winding, and probably just a few turns too. If you rewired this part of the radio, make sure the windings were not switched around. If connected wrong, the tickler would not resonate at the correct frequency with the tuning/trimmer caps C-3. In addition, a simple continuity test of each winding does not measure the inductance, hence a few shorted turns could have the primary tank circuit oscillating well above the required freq. If you have an oscilloscope, this can be verified. You might be able to feed modulated RF into the antenna circuit, and try frequencies above std BC to see if an IF frequency or birdie is detected. Is there a voltage across R-2, which would indicate the tube is drawing current and trying to oscillate?
:
:marv
:
::Radiodoc,
:: I just tried that and it makes absolutely no difference whatsoever.
:: What do I look at next?
::
::Thanks,
::
:::Dave,
:::
:::The 98 volts is probably ok. If all else failed and as a shot in the dark, I would reverse the coil leads on the non-tuned winding between B+ and the oscillator "plate" and see what happens.
:::
:::Radiodoc
:::***************
:::
::::Radiodoc,
:::: I took out the oscillator coil and checked every connection and all are good (Perfect), no opens. I checked and cleaned the band switch several times. I replaced C9 several times. When I connect 456 Kc to it from my RF signal generator, it receives that tone perfectly. It blasts!! But it wont take what's presented to it from the antenna terminals and convert that to 456 Kc. It absolutely refuses to do that under any circumstances.
:::: I checked all the connections and they are perfectly perfectly perfect. The resistors are all the correct values. The solder connections have been re-done and they are nice and shiny.
:::: I tried 3 different 6A7 tubes and none of them make any difference.
:::: I checked to make sure that the tuning capacitor or trimmer have any shorts on the oscillator side and there are no shorts. When the set is on and I try to adjust the oscillator screw or short the rotor with the stator on the oscillator side it makes no difference at all. All it's doing is "TRFing". The person who owns this radio MUST have the radio working immediately. I must continue working on it until it works. What do I do next? How do I convert it to a TRF receiver?
::::
::::Thanks,
::::
::::Dave
:::::Radiodoc,
::::: B+ is 98 volts. Is that low? Shouldn't it be a little higher? I can't see any way to raise it. Filament voltage on the 6A7 is 5.3 volts.
:::::
:::::Thanks,
:::::
:::::Dave
::::::Radiodoc,
:::::: C9 is a 100 pf capacitor. I replaced it and it made absolutely no difference.
::::::
::::::Dave
:::::::Dave,
:::::::
:::::::If all fails, walk away for a while and then come back and check carefully all the wiring around the osc circuit for correctness and good solder joints. Did you check C9 (probably a mica)or replace it. If not may try substituting another. Voltage checks on the stage may give a clue if any are off very much.
:::::::
:::::::Radiodoc
:::::::***********
:::::::
:::::::
::::::::Hello All,
:::::::: I have checked everything and the oscillator absolutely refuses to work. All paper and filter capacitors have been replaced. No part of the oscillator coil is open. The resistors are good. I tried a few 6A7s and it still wont work. What to I look at next?
:::::::: This is an AC/DC set. There's not that much there.
::::::::
::::::::Thanks,
::::::::
::::::::Dave
R2 is the resistor shaped like a capacitor and 2.87 volts is across it when the radio is on. Does that mean anything?
Thanks,
Dave
:Marv,
: There's no short at C3. I disconnected the wire from the band switch and nothing is shorted. The tuning capacitor has no shorts in either section and the trimmers don't have shorts either.
: I will check for a voltage across R2 and let you know what I've found.
:
:Thanks,
:
:Dave
::Dave,
::Be absolutely sure that neither caps at C3 location are shorted. The so called secondary (right side of
::T-2)is a non resonant feedback or tickler winding, and probably just a few turns too. If you rewired this part of the radio, make sure the windings were not switched around. If connected wrong, the tickler would not resonate at the correct frequency with the tuning/trimmer caps C-3. In addition, a simple continuity test of each winding does not measure the inductance, hence a few shorted turns could have the primary tank circuit oscillating well above the required freq. If you have an oscilloscope, this can be verified. You might be able to feed modulated RF into the antenna circuit, and try frequencies above std BC to see if an IF frequency or birdie is detected. Is there a voltage across R-2, which would indicate the tube is drawing current and trying to oscillate?
::
::marv
::
:::Radiodoc,
::: I just tried that and it makes absolutely no difference whatsoever.
::: What do I look at next?
:::
:::Thanks,
:::
::::Dave,
::::
::::The 98 volts is probably ok. If all else failed and as a shot in the dark, I would reverse the coil leads on the non-tuned winding between B+ and the oscillator "plate" and see what happens.
::::
::::Radiodoc
::::***************
::::
:::::Radiodoc,
::::: I took out the oscillator coil and checked every connection and all are good (Perfect), no opens. I checked and cleaned the band switch several times. I replaced C9 several times. When I connect 456 Kc to it from my RF signal generator, it receives that tone perfectly. It blasts!! But it wont take what's presented to it from the antenna terminals and convert that to 456 Kc. It absolutely refuses to do that under any circumstances.
::::: I checked all the connections and they are perfectly perfectly perfect. The resistors are all the correct values. The solder connections have been re-done and they are nice and shiny.
::::: I tried 3 different 6A7 tubes and none of them make any difference.
::::: I checked to make sure that the tuning capacitor or trimmer have any shorts on the oscillator side and there are no shorts. When the set is on and I try to adjust the oscillator screw or short the rotor with the stator on the oscillator side it makes no difference at all. All it's doing is "TRFing". The person who owns this radio MUST have the radio working immediately. I must continue working on it until it works. What do I do next? How do I convert it to a TRF receiver?
:::::
:::::Thanks,
:::::
:::::Dave
::::::Radiodoc,
:::::: B+ is 98 volts. Is that low? Shouldn't it be a little higher? I can't see any way to raise it. Filament voltage on the 6A7 is 5.3 volts.
::::::
::::::Thanks,
::::::
::::::Dave
:::::::Radiodoc,
::::::: C9 is a 100 pf capacitor. I replaced it and it made absolutely no difference.
:::::::
:::::::Dave
::::::::Dave,
::::::::
::::::::If all fails, walk away for a while and then come back and check carefully all the wiring around the osc circuit for correctness and good solder joints. Did you check C9 (probably a mica)or replace it. If not may try substituting another. Voltage checks on the stage may give a clue if any are off very much.
::::::::
::::::::Radiodoc
::::::::***********
::::::::
::::::::
:::::::::Hello All,
::::::::: I have checked everything and the oscillator absolutely refuses to work. All paper and filter capacitors have been replaced. No part of the oscillator coil is open. The resistors are good. I tried a few 6A7s and it still wont work. What to I look at next?
::::::::: This is an AC/DC set. There's not that much there.
:::::::::
:::::::::Thanks,
:::::::::
:::::::::Dave
Did you check the resistors with a high impedance DVM. I have had problems in the past using a DVM and the resistor measuring within tolerance only to find out that when removed from the circuit or measured with a 20K/voltohm meter that the resistor in fact measured considerably higher out of tolerance. Never did figure out why this happened or perhaps it was just my DVM.
Radiodoc
**********
:Marv,
: R2 is the resistor shaped like a capacitor and 2.87 volts is across it when the radio is on. Does that mean anything?
:
:Thanks,
:
:Dave
::Marv,
:: There's no short at C3. I disconnected the wire from the band switch and nothing is shorted. The tuning capacitor has no shorts in either section and the trimmers don't have shorts either.
:: I will check for a voltage across R2 and let you know what I've found.
::
::Thanks,
::
::Dave
:::Dave,
:::Be absolutely sure that neither caps at C3 location are shorted. The so called secondary (right side of
:::T-2)is a non resonant feedback or tickler winding, and probably just a few turns too. If you rewired this part of the radio, make sure the windings were not switched around. If connected wrong, the tickler would not resonate at the correct frequency with the tuning/trimmer caps C-3. In addition, a simple continuity test of each winding does not measure the inductance, hence a few shorted turns could have the primary tank circuit oscillating well above the required freq. If you have an oscilloscope, this can be verified. You might be able to feed modulated RF into the antenna circuit, and try frequencies above std BC to see if an IF frequency or birdie is detected. Is there a voltage across R-2, which would indicate the tube is drawing current and trying to oscillate?
:::
:::marv
:::
::::Radiodoc,
:::: I just tried that and it makes absolutely no difference whatsoever.
:::: What do I look at next?
::::
::::Thanks,
::::
:::::Dave,
:::::
:::::The 98 volts is probably ok. If all else failed and as a shot in the dark, I would reverse the coil leads on the non-tuned winding between B+ and the oscillator "plate" and see what happens.
:::::
:::::Radiodoc
:::::***************
:::::
::::::Radiodoc,
:::::: I took out the oscillator coil and checked every connection and all are good (Perfect), no opens. I checked and cleaned the band switch several times. I replaced C9 several times. When I connect 456 Kc to it from my RF signal generator, it receives that tone perfectly. It blasts!! But it wont take what's presented to it from the antenna terminals and convert that to 456 Kc. It absolutely refuses to do that under any circumstances.
:::::: I checked all the connections and they are perfectly perfectly perfect. The resistors are all the correct values. The solder connections have been re-done and they are nice and shiny.
:::::: I tried 3 different 6A7 tubes and none of them make any difference.
:::::: I checked to make sure that the tuning capacitor or trimmer have any shorts on the oscillator side and there are no shorts. When the set is on and I try to adjust the oscillator screw or short the rotor with the stator on the oscillator side it makes no difference at all. All it's doing is "TRFing". The person who owns this radio MUST have the radio working immediately. I must continue working on it until it works. What do I do next? How do I convert it to a TRF receiver?
::::::
::::::Thanks,
::::::
::::::Dave
:::::::Radiodoc,
::::::: B+ is 98 volts. Is that low? Shouldn't it be a little higher? I can't see any way to raise it. Filament voltage on the 6A7 is 5.3 volts.
:::::::
:::::::Thanks,
:::::::
:::::::Dave
::::::::Radiodoc,
:::::::: C9 is a 100 pf capacitor. I replaced it and it made absolutely no difference.
::::::::
::::::::Dave
:::::::::Dave,
:::::::::
:::::::::If all fails, walk away for a while and then come back and check carefully all the wiring around the osc circuit for correctness and good solder joints. Did you check C9 (probably a mica)or replace it. If not may try substituting another. Voltage checks on the stage may give a clue if any are off very much.
:::::::::
:::::::::Radiodoc
:::::::::***********
:::::::::
:::::::::
::::::::::Hello All,
:::::::::: I have checked everything and the oscillator absolutely refuses to work. All paper and filter capacitors have been replaced. No part of the oscillator coil is open. The resistors are good. I tried a few 6A7s and it still wont work. What to I look at next?
:::::::::: This is an AC/DC set. There's not that much there.
::::::::::
::::::::::Thanks,
::::::::::
::::::::::Dave
In reading your 2 posts, I assume the set never worked and you re-capped and replaced bad resistors first. In this case, did you replace the parts just as they were originally installed, but did you also verify their placement via the schematic?
marv
:Radiodoc,
: I just tried that and it makes absolutely no difference whatsoever.
: What do I look at next?
:
:Thanks,
:
::Dave,
::
::The 98 volts is probably ok. If all else failed and as a shot in the dark, I would reverse the coil leads on the non-tuned winding between B+ and the oscillator "plate" and see what happens.
::
::Radiodoc
::***************
::
:::Radiodoc,
::: I took out the oscillator coil and checked every connection and all are good (Perfect), no opens. I checked and cleaned the band switch several times. I replaced C9 several times. When I connect 456 Kc to it from my RF signal generator, it receives that tone perfectly. It blasts!! But it wont take what's presented to it from the antenna terminals and convert that to 456 Kc. It absolutely refuses to do that under any circumstances.
::: I checked all the connections and they are perfectly perfectly perfect. The resistors are all the correct values. The solder connections have been re-done and they are nice and shiny.
::: I tried 3 different 6A7 tubes and none of them make any difference.
::: I checked to make sure that the tuning capacitor or trimmer have any shorts on the oscillator side and there are no shorts. When the set is on and I try to adjust the oscillator screw or short the rotor with the stator on the oscillator side it makes no difference at all. All it's doing is "TRFing". The person who owns this radio MUST have the radio working immediately. I must continue working on it until it works. What do I do next? How do I convert it to a TRF receiver?
:::
:::Thanks,
:::
:::Dave
::::Radiodoc,
:::: B+ is 98 volts. Is that low? Shouldn't it be a little higher? I can't see any way to raise it. Filament voltage on the 6A7 is 5.3 volts.
::::
::::Thanks,
::::
::::Dave
:::::Radiodoc,
::::: C9 is a 100 pf capacitor. I replaced it and it made absolutely no difference.
:::::
:::::Dave
::::::Dave,
::::::
::::::If all fails, walk away for a while and then come back and check carefully all the wiring around the osc circuit for correctness and good solder joints. Did you check C9 (probably a mica)or replace it. If not may try substituting another. Voltage checks on the stage may give a clue if any are off very much.
::::::
::::::Radiodoc
::::::***********
::::::
::::::
:::::::Hello All,
::::::: I have checked everything and the oscillator absolutely refuses to work. All paper and filter capacitors have been replaced. No part of the oscillator coil is open. The resistors are good. I tried a few 6A7s and it still wont work. What to I look at next?
::::::: This is an AC/DC set. There's not that much there.
:::::::
:::::::Thanks,
:::::::
:::::::Dave
The resistors are the correct value. I checked them. I never replaced them. I also knew that the long black capacitor looking devices were also resistors. They are all correct. The capacitors are in the correct places. Nothing has been changed.
I'll check the voltage and double check for "birdies". I think I did hear them. My huge isolation transformer is getting a lot of use on this restoration.
Thanks,
Dave
:Dave,
:In reading your 2 posts, I assume the set never worked and you re-capped and replaced bad resistors first. In this case, did you replace the parts just as they were originally installed, but did you also verify their placement via the schematic?
:
:marv
:
::Radiodoc,
:: I just tried that and it makes absolutely no difference whatsoever.
:: What do I look at next?
::
::Thanks,
::
:::Dave,
:::
:::The 98 volts is probably ok. If all else failed and as a shot in the dark, I would reverse the coil leads on the non-tuned winding between B+ and the oscillator "plate" and see what happens.
:::
:::Radiodoc
:::***************
:::
::::Radiodoc,
:::: I took out the oscillator coil and checked every connection and all are good (Perfect), no opens. I checked and cleaned the band switch several times. I replaced C9 several times. When I connect 456 Kc to it from my RF signal generator, it receives that tone perfectly. It blasts!! But it wont take what's presented to it from the antenna terminals and convert that to 456 Kc. It absolutely refuses to do that under any circumstances.
:::: I checked all the connections and they are perfectly perfectly perfect. The resistors are all the correct values. The solder connections have been re-done and they are nice and shiny.
:::: I tried 3 different 6A7 tubes and none of them make any difference.
:::: I checked to make sure that the tuning capacitor or trimmer have any shorts on the oscillator side and there are no shorts. When the set is on and I try to adjust the oscillator screw or short the rotor with the stator on the oscillator side it makes no difference at all. All it's doing is "TRFing". The person who owns this radio MUST have the radio working immediately. I must continue working on it until it works. What do I do next? How do I convert it to a TRF receiver?
::::
::::Thanks,
::::
::::Dave
:::::Radiodoc,
::::: B+ is 98 volts. Is that low? Shouldn't it be a little higher? I can't see any way to raise it. Filament voltage on the 6A7 is 5.3 volts.
:::::
:::::Thanks,
:::::
:::::Dave
::::::Radiodoc,
:::::: C9 is a 100 pf capacitor. I replaced it and it made absolutely no difference.
::::::
::::::Dave
:::::::Dave,
:::::::
:::::::If all fails, walk away for a while and then come back and check carefully all the wiring around the osc circuit for correctness and good solder joints. Did you check C9 (probably a mica)or replace it. If not may try substituting another. Voltage checks on the stage may give a clue if any are off very much.
:::::::
:::::::Radiodoc
:::::::***********
:::::::
:::::::
::::::::Hello All,
:::::::: I have checked everything and the oscillator absolutely refuses to work. All paper and filter capacitors have been replaced. No part of the oscillator coil is open. The resistors are good. I tried a few 6A7s and it still wont work. What to I look at next?
:::::::: This is an AC/DC set. There's not that much there.
::::::::
::::::::Thanks,
::::::::
::::::::Dave
The oscillator has 2 trimmers in BC mode. One on the tuning cap (C-3) and the other at the rear (C-5), either of which could hamper operation if misadjusted. The one at C-3 is common to both SW and BC. Check C-18. Also, when you tested the IF, (456kHz) were you using signal levels low to moderate or high enough to blast through at any freq?
marv
:Marv,
: The resistors are the correct value. I checked them. I never replaced them. I also knew that the long black capacitor looking devices were also resistors. They are all correct. The capacitors are in the correct places. Nothing has been changed.
: I'll check the voltage and double check for "birdies". I think I did hear them. My huge isolation transformer is getting a lot of use on this restoration.
:
:Thanks,
:
:Dave
:
::Dave,
::In reading your 2 posts, I assume the set never worked and you re-capped and replaced bad resistors first. In this case, did you replace the parts just as they were originally installed, but did you also verify their placement via the schematic?
::
::marv
::
:::Radiodoc,
::: I just tried that and it makes absolutely no difference whatsoever.
::: What do I look at next?
:::
:::Thanks,
:::
::::Dave,
::::
::::The 98 volts is probably ok. If all else failed and as a shot in the dark, I would reverse the coil leads on the non-tuned winding between B+ and the oscillator "plate" and see what happens.
::::
::::Radiodoc
::::***************
::::
:::::Radiodoc,
::::: I took out the oscillator coil and checked every connection and all are good (Perfect), no opens. I checked and cleaned the band switch several times. I replaced C9 several times. When I connect 456 Kc to it from my RF signal generator, it receives that tone perfectly. It blasts!! But it wont take what's presented to it from the antenna terminals and convert that to 456 Kc. It absolutely refuses to do that under any circumstances.
::::: I checked all the connections and they are perfectly perfectly perfect. The resistors are all the correct values. The solder connections have been re-done and they are nice and shiny.
::::: I tried 3 different 6A7 tubes and none of them make any difference.
::::: I checked to make sure that the tuning capacitor or trimmer have any shorts on the oscillator side and there are no shorts. When the set is on and I try to adjust the oscillator screw or short the rotor with the stator on the oscillator side it makes no difference at all. All it's doing is "TRFing". The person who owns this radio MUST have the radio working immediately. I must continue working on it until it works. What do I do next? How do I convert it to a TRF receiver?
:::::
:::::Thanks,
:::::
:::::Dave
::::::Radiodoc,
:::::: B+ is 98 volts. Is that low? Shouldn't it be a little higher? I can't see any way to raise it. Filament voltage on the 6A7 is 5.3 volts.
::::::
::::::Thanks,
::::::
::::::Dave
:::::::Radiodoc,
::::::: C9 is a 100 pf capacitor. I replaced it and it made absolutely no difference.
:::::::
:::::::Dave
::::::::Dave,
::::::::
::::::::If all fails, walk away for a while and then come back and check carefully all the wiring around the osc circuit for correctness and good solder joints. Did you check C9 (probably a mica)or replace it. If not may try substituting another. Voltage checks on the stage may give a clue if any are off very much.
::::::::
::::::::Radiodoc
::::::::***********
::::::::
::::::::
:::::::::Hello All,
::::::::: I have checked everything and the oscillator absolutely refuses to work. All paper and filter capacitors have been replaced. No part of the oscillator coil is open. The resistors are good. I tried a few 6A7s and it still wont work. What to I look at next?
::::::::: This is an AC/DC set. There's not that much there.
:::::::::
:::::::::Thanks,
:::::::::
:::::::::Dave
My RF signal generator modulates a 400 Hz tone on the 456 Kc carrier frequency when it's set to 456 Kc. The part of the radio that the signal generator is connected to is tune to exactly tuned to 456 Kc. It can receive 456 Kc and only 456 Kc. That "station" is received and I can blast the 400 Hz tone through the speaker of the radio. If I change the RF signal generator to another frequency, then no 400 Hz tone is heard. It is as perfectly aligned as I can get it. It may not have the best adjacent channel rejection but the signal is the strongest when the signal generator is set to 456 Kc.
The front part of the radio is what I'm having trouble with, and NOT the 456 Kc area. The radio is not converting (moving) the received frequency to 456 Kc. I can hear 570 Kc near the low end of the band and 620 Kc near the high end of the band (I live right near the brodcast antennas for these stations). That's all it does. It absolutely refuses to oscillate under any circumstances. I have checked about all I can check. All is working and not working at the same time.
The trimmers you are talking about are the oscillator trimmers that can only do anything, are only active, if the oscillator is working. I can put them in any position and they do nothing. They aren't shorted. They are perfectly good but not active because the oscillator is dead.
C-18 is brand new. It doesn't have any problems. One end is connected to the chassis and the other end is connected to a resistor. R3. I'll double check that it's also connected to the dead oscillator coil. It's not open. It just refuses to oscillate. All 11 paper and 2 electrolytic capacitors have been replaced. The positives of the electrolytic capacitors connect to the same place and the negatives connect to two different places.
I am getting close to removing the oscillator coil and replacing it or rewinding this one. If only I had the specs for this one. The part number on it is: 2DT200. Maybe someone has an Emerson specs book.
Thanks,
Dave
:Dave,
:The oscillator has 2 trimmers in BC mode. One on the tuning cap (C-3) and the other at the rear (C-5), either of which could hamper operation if misadjusted. The one at C-3 is common to both SW and BC. Check C-18. Also, when you tested the IF, (456kHz) were you using signal levels low to moderate or high enough to blast through at any freq?
:
:marv
:
::Marv,
:: The resistors are the correct value. I checked them. I never replaced them. I also knew that the long black capacitor looking devices were also resistors. They are all correct. The capacitors are in the correct places. Nothing has been changed.
:: I'll check the voltage and double check for "birdies". I think I did hear them. My huge isolation transformer is getting a lot of use on this restoration.
::
::Thanks,
::
::Dave
::
:::Dave,
:::In reading your 2 posts, I assume the set never worked and you re-capped and replaced bad resistors first. In this case, did you replace the parts just as they were originally installed, but did you also verify their placement via the schematic?
:::
:::marv
:::
::::Radiodoc,
:::: I just tried that and it makes absolutely no difference whatsoever.
:::: What do I look at next?
::::
::::Thanks,
::::
:::::Dave,
:::::
:::::The 98 volts is probably ok. If all else failed and as a shot in the dark, I would reverse the coil leads on the non-tuned winding between B+ and the oscillator "plate" and see what happens.
:::::
:::::Radiodoc
:::::***************
:::::
::::::Radiodoc,
:::::: I took out the oscillator coil and checked every connection and all are good (Perfect), no opens. I checked and cleaned the band switch several times. I replaced C9 several times. When I connect 456 Kc to it from my RF signal generator, it receives that tone perfectly. It blasts!! But it wont take what's presented to it from the antenna terminals and convert that to 456 Kc. It absolutely refuses to do that under any circumstances.
:::::: I checked all the connections and they are perfectly perfectly perfect. The resistors are all the correct values. The solder connections have been re-done and they are nice and shiny.
:::::: I tried 3 different 6A7 tubes and none of them make any difference.
:::::: I checked to make sure that the tuning capacitor or trimmer have any shorts on the oscillator side and there are no shorts. When the set is on and I try to adjust the oscillator screw or short the rotor with the stator on the oscillator side it makes no difference at all. All it's doing is "TRFing". The person who owns this radio MUST have the radio working immediately. I must continue working on it until it works. What do I do next? How do I convert it to a TRF receiver?
::::::
::::::Thanks,
::::::
::::::Dave
:::::::Radiodoc,
::::::: B+ is 98 volts. Is that low? Shouldn't it be a little higher? I can't see any way to raise it. Filament voltage on the 6A7 is 5.3 volts.
:::::::
:::::::Thanks,
:::::::
:::::::Dave
::::::::Radiodoc,
:::::::: C9 is a 100 pf capacitor. I replaced it and it made absolutely no difference.
::::::::
::::::::Dave
:::::::::Dave,
:::::::::
:::::::::If all fails, walk away for a while and then come back and check carefully all the wiring around the osc circuit for correctness and good solder joints. Did you check C9 (probably a mica)or replace it. If not may try substituting another. Voltage checks on the stage may give a clue if any are off very much.
:::::::::
:::::::::Radiodoc
:::::::::***********
:::::::::
:::::::::
::::::::::Hello All,
:::::::::: I have checked everything and the oscillator absolutely refuses to work. All paper and filter capacitors have been replaced. No part of the oscillator coil is open. The resistors are good. I tried a few 6A7s and it still wont work. What to I look at next?
:::::::::: This is an AC/DC set. There's not that much there.
::::::::::
::::::::::Thanks,
::::::::::
::::::::::Dave
Google "pentagrid converters", clik on Wikapedia, scroll down to "other links" and clik on 2A7-6A7. The old RCA tube manual page 55 has design info, including coil data, which may be helpful if deciding to rewind/test the coil. Using basic math, wire and the coil winding data, may get you a ballpark DC resistance value of the oscillator coil's windings. Those 2 stations (520kHz/620kHz) must be really powerful to get through the 456kHz IF circuitry.
marv
:Marv,
: My RF signal generator modulates a 400 Hz tone on the 456 Kc carrier frequency when it's set to 456 Kc. The part of the radio that the signal generator is connected to is tune to exactly tuned to 456 Kc. It can receive 456 Kc and only 456 Kc. That "station" is received and I can blast the 400 Hz tone through the speaker of the radio. If I change the RF signal generator to another frequency, then no 400 Hz tone is heard. It is as perfectly aligned as I can get it. It may not have the best adjacent channel rejection but the signal is the strongest when the signal generator is set to 456 Kc.
: The front part of the radio is what I'm having trouble with, and NOT the 456 Kc area. The radio is not converting (moving) the received frequency to 456 Kc. I can hear 570 Kc near the low end of the band and 620 Kc near the high end of the band (I live right near the brodcast antennas for these stations). That's all it does. It absolutely refuses to oscillate under any circumstances. I have checked about all I can check. All is working and not working at the same time.
: The trimmers you are talking about are the oscillator trimmers that can only do anything, are only active, if the oscillator is working. I can put them in any position and they do nothing. They aren't shorted. They are perfectly good but not active because the oscillator is dead.
: C-18 is brand new. It doesn't have any problems. One end is connected to the chassis and the other end is connected to a resistor. R3. I'll double check that it's also connected to the dead oscillator coil. It's not open. It just refuses to oscillate. All 11 paper and 2 electrolytic capacitors have been replaced. The positives of the electrolytic capacitors connect to the same place and the negatives connect to two different places.
: I am getting close to removing the oscillator coil and replacing it or rewinding this one. If only I had the specs for this one. The part number on it is: 2DT200. Maybe someone has an Emerson specs book.
:
:Thanks,
:
:Dave
:
::Dave,
::The oscillator has 2 trimmers in BC mode. One on the tuning cap (C-3) and the other at the rear (C-5), either of which could hamper operation if misadjusted. The one at C-3 is common to both SW and BC. Check C-18. Also, when you tested the IF, (456kHz) were you using signal levels low to moderate or high enough to blast through at any freq?
::
::marv
::
:::Marv,
::: The resistors are the correct value. I checked them. I never replaced them. I also knew that the long black capacitor looking devices were also resistors. They are all correct. The capacitors are in the correct places. Nothing has been changed.
::: I'll check the voltage and double check for "birdies". I think I did hear them. My huge isolation transformer is getting a lot of use on this restoration.
:::
:::Thanks,
:::
:::Dave
:::
::::Dave,
::::In reading your 2 posts, I assume the set never worked and you re-capped and replaced bad resistors first. In this case, did you replace the parts just as they were originally installed, but did you also verify their placement via the schematic?
::::
::::marv
::::
:::::Radiodoc,
::::: I just tried that and it makes absolutely no difference whatsoever.
::::: What do I look at next?
:::::
:::::Thanks,
:::::
::::::Dave,
::::::
::::::The 98 volts is probably ok. If all else failed and as a shot in the dark, I would reverse the coil leads on the non-tuned winding between B+ and the oscillator "plate" and see what happens.
::::::
::::::Radiodoc
::::::***************
::::::
:::::::Radiodoc,
::::::: I took out the oscillator coil and checked every connection and all are good (Perfect), no opens. I checked and cleaned the band switch several times. I replaced C9 several times. When I connect 456 Kc to it from my RF signal generator, it receives that tone perfectly. It blasts!! But it wont take what's presented to it from the antenna terminals and convert that to 456 Kc. It absolutely refuses to do that under any circumstances.
::::::: I checked all the connections and they are perfectly perfectly perfect. The resistors are all the correct values. The solder connections have been re-done and they are nice and shiny.
::::::: I tried 3 different 6A7 tubes and none of them make any difference.
::::::: I checked to make sure that the tuning capacitor or trimmer have any shorts on the oscillator side and there are no shorts. When the set is on and I try to adjust the oscillator screw or short the rotor with the stator on the oscillator side it makes no difference at all. All it's doing is "TRFing". The person who owns this radio MUST have the radio working immediately. I must continue working on it until it works. What do I do next? How do I convert it to a TRF receiver?
:::::::
:::::::Thanks,
:::::::
:::::::Dave
::::::::Radiodoc,
:::::::: B+ is 98 volts. Is that low? Shouldn't it be a little higher? I can't see any way to raise it. Filament voltage on the 6A7 is 5.3 volts.
::::::::
::::::::Thanks,
::::::::
::::::::Dave
:::::::::Radiodoc,
::::::::: C9 is a 100 pf capacitor. I replaced it and it made absolutely no difference.
:::::::::
:::::::::Dave
::::::::::Dave,
::::::::::
::::::::::If all fails, walk away for a while and then come back and check carefully all the wiring around the osc circuit for correctness and good solder joints. Did you check C9 (probably a mica)or replace it. If not may try substituting another. Voltage checks on the stage may give a clue if any are off very much.
::::::::::
::::::::::Radiodoc
::::::::::***********
::::::::::
::::::::::
:::::::::::Hello All,
::::::::::: I have checked everything and the oscillator absolutely refuses to work. All paper and filter capacitors have been replaced. No part of the oscillator coil is open. The resistors are good. I tried a few 6A7s and it still wont work. What to I look at next?
::::::::::: This is an AC/DC set. There's not that much there.
:::::::::::
:::::::::::Thanks,
:::::::::::
:::::::::::Dave
Here are the voltage readings on the 6A7 tube.
Pins 1 & 7: 6.8 volts AC (Filament)
Pin 2: 107.5 v DC (Plate)
Pin 3: 43.5 volts DC (G3 and G5)
Pin 4: 106.7 volts (G2)
Pin 5: 2.2 V DC (G1)
Pin 6: 2.647 volts DC (Cathode)
Cap: -.361 v DC (G4)
These seem like pretty healthy voltages to me. I don't see anything wrong there. The IF transformer is connecting B+ to the plate and the Oscillator coil is connecting B+ to to pin 4. So neither coil is open.
I did notice that C17 was missing. I put it back and it might have made an improvement but not with the oscillator.
Please if anyone has anymore ideas before I "attack" (very closely examine) the oscillator coil, please help.
Thanks,
Dave
:Marv,
: My RF signal generator modulates a 400 Hz tone on the 456 Kc carrier frequency when it's set to 456 Kc. The part of the radio that the signal generator is connected to is tune to exactly tuned to 456 Kc. It can receive 456 Kc and only 456 Kc. That "station" is received and I can blast the 400 Hz tone through the speaker of the radio. If I change the RF signal generator to another frequency, then no 400 Hz tone is heard. It is as perfectly aligned as I can get it. It may not have the best adjacent channel rejection but the signal is the strongest when the signal generator is set to 456 Kc.
: The front part of the radio is what I'm having trouble with, and NOT the 456 Kc area. The radio is not converting (moving) the received frequency to 456 Kc. I can hear 570 Kc near the low end of the band and 620 Kc near the high end of the band (I live right near the brodcast antennas for these stations). That's all it does. It absolutely refuses to oscillate under any circumstances. I have checked about all I can check. All is working and not working at the same time.
: The trimmers you are talking about are the oscillator trimmers that can only do anything, are only active, if the oscillator is working. I can put them in any position and they do nothing. They aren't shorted. They are perfectly good but not active because the oscillator is dead.
: C-18 is brand new. It doesn't have any problems. One end is connected to the chassis and the other end is connected to a resistor. R3. I'll double check that it's also connected to the dead oscillator coil. It's not open. It just refuses to oscillate. All 11 paper and 2 electrolytic capacitors have been replaced. The positives of the electrolytic capacitors connect to the same place and the negatives connect to two different places.
: I am getting close to removing the oscillator coil and replacing it or rewinding this one. If only I had the specs for this one. The part number on it is: 2DT200. Maybe someone has an Emerson specs book.
:
:Thanks,
:
:Dave
:
::Dave,
::The oscillator has 2 trimmers in BC mode. One on the tuning cap (C-3) and the other at the rear (C-5), either of which could hamper operation if misadjusted. The one at C-3 is common to both SW and BC. Check C-18. Also, when you tested the IF, (456kHz) were you using signal levels low to moderate or high enough to blast through at any freq?
::
::marv
::
:::Marv,
::: The resistors are the correct value. I checked them. I never replaced them. I also knew that the long black capacitor looking devices were also resistors. They are all correct. The capacitors are in the correct places. Nothing has been changed.
::: I'll check the voltage and double check for "birdies". I think I did hear them. My huge isolation transformer is getting a lot of use on this restoration.
:::
:::Thanks,
:::
:::Dave
:::
::::Dave,
::::In reading your 2 posts, I assume the set never worked and you re-capped and replaced bad resistors first. In this case, did you replace the parts just as they were originally installed, but did you also verify their placement via the schematic?
::::
::::marv
::::
:::::Radiodoc,
::::: I just tried that and it makes absolutely no difference whatsoever.
::::: What do I look at next?
:::::
:::::Thanks,
:::::
::::::Dave,
::::::
::::::The 98 volts is probably ok. If all else failed and as a shot in the dark, I would reverse the coil leads on the non-tuned winding between B+ and the oscillator "plate" and see what happens.
::::::
::::::Radiodoc
::::::***************
::::::
:::::::Radiodoc,
::::::: I took out the oscillator coil and checked every connection and all are good (Perfect), no opens. I checked and cleaned the band switch several times. I replaced C9 several times. When I connect 456 Kc to it from my RF signal generator, it receives that tone perfectly. It blasts!! But it wont take what's presented to it from the antenna terminals and convert that to 456 Kc. It absolutely refuses to do that under any circumstances.
::::::: I checked all the connections and they are perfectly perfectly perfect. The resistors are all the correct values. The solder connections have been re-done and they are nice and shiny.
::::::: I tried 3 different 6A7 tubes and none of them make any difference.
::::::: I checked to make sure that the tuning capacitor or trimmer have any shorts on the oscillator side and there are no shorts. When the set is on and I try to adjust the oscillator screw or short the rotor with the stator on the oscillator side it makes no difference at all. All it's doing is "TRFing". The person who owns this radio MUST have the radio working immediately. I must continue working on it until it works. What do I do next? How do I convert it to a TRF receiver?
:::::::
:::::::Thanks,
:::::::
:::::::Dave
::::::::Radiodoc,
:::::::: B+ is 98 volts. Is that low? Shouldn't it be a little higher? I can't see any way to raise it. Filament voltage on the 6A7 is 5.3 volts.
::::::::
::::::::Thanks,
::::::::
::::::::Dave
:::::::::Radiodoc,
::::::::: C9 is a 100 pf capacitor. I replaced it and it made absolutely no difference.
:::::::::
:::::::::Dave
::::::::::Dave,
::::::::::
::::::::::If all fails, walk away for a while and then come back and check carefully all the wiring around the osc circuit for correctness and good solder joints. Did you check C9 (probably a mica)or replace it. If not may try substituting another. Voltage checks on the stage may give a clue if any are off very much.
::::::::::
::::::::::Radiodoc
::::::::::***********
::::::::::
::::::::::
:::::::::::Hello All,
::::::::::: I have checked everything and the oscillator absolutely refuses to work. All paper and filter capacitors have been replaced. No part of the oscillator coil is open. The resistors are good. I tried a few 6A7s and it still wont work. What to I look at next?
::::::::::: This is an AC/DC set. There's not that much there.
:::::::::::
:::::::::::Thanks,
:::::::::::
:::::::::::Dave
After reviewing your last postings info:
My fustus “querstion” was if the radio operated in some degree of receiving stations ? via a tunable superheterodyne action / mode prior to the mass recapping of the unit ?
Can we assume that C9..100 mmfd was ok and not even messed with ?
Is cathode resistor R2 wired up ok and at its ~350 ohm value ?
As well as the grid resistor of R1 ….50k wired properly and at its value ?
The last item which I am sure that you did get involved with was the cathode bypass Condenser C7….05 ufd and it is OK and was reinstalled to the correct terminals…right…as that is also as critical as the 3 companion items.
Looks as if the oscillator coil is on the larger ½ to ¾ in coil form and and a Litz wound unit in a tight layer…rather than the old style of enameled wire wound the full length of a long coil form. Plus, you seem to attest of its wirings continuity integrity as well as the adjunct tuning cap and its trimmer caps not being shorted out or dragging plates. Plus the additional reverting of one of the windings for a proper feed back phase check.
Also with your BEE und KAY, you should be able to couple its input into the first grid of the mixer and at the proper injection of CW RF level, be able to swing its dial thru the 1005-2195 khc range and tune thru your stronger receptive stations in the area, with the two “TRF” stations being the powerhouses, BUT with the necessity of having to manually tune the tuning condenser in order to optimize the RF section being in resonance with them, when trying for weaker stations in bringing up received reception level..
To further ease your mind about the radios oscillator sections L-C combinations , you could go to the juncture of C9 and R1 and couple in CW RF via a series / isolative ~100 pf cap and go to the same junction and tack on an anode of a 1N34 / 60 / 64 / 270 GERMANIUM diode and at its cathodes end , take a .001 cap for bypassing to ground and then meter the cathodes output via a VTVM.
(N0…1N 914’s/4148’s/1N400oseries for this application)(Radio Shack stocks them in case you don’t have one from an oooold generation AM transistor radio chassis or from the building of a crystal set.)
Then if you will power up the BEE und KAY and place in its CW mode and set the Emerson…(No power required....as this testing will be passive)…to the 1/3 lower end of the dial 700 kc ish (tuning cap ~ ¾ meshed)
Then you tune the B & K in the ~1000-1400 range and see if the co-joined parasitic tuned oscillators circuit doesn’t give you a rising / declining reading as resonance was scanned across.
Then, hop the radios tuning up to the higher third of the band (tuning cap ~ 1/4 meshed) and test for a like reading of a viable resonant circuit pair working at that
frequency also.
Thereby you have merely temp- rigged up a “po boys” grid dipper to interpret the presence of a functioning / resonating effect by the osc sections variable L-C pair and it having some degree of “Q”.
The other alternative being that recurrent sweep Eico 460 Scope / Kluge of yours, so I think that with the former detected and metered RF , you would be much better off.
Addenda:
Noticed your new readings just at this posting time, and the bucolic local osc grid voltages reading. And have you confirmed that there is even any level oscillation by the taking of a portable xstr radios ferri-loop and placing it atop the osc coil winding and tune it off station just onto the very edge / sideband of a weaker ~1400-1740 kc AM station and then run the operating radio's tuning condenser across the bottom half of the AM band to see if even a weak heterodyning / birdie is heard on the xstr radio.
Standing by for feed back
73's de Edd
:Marv and all,
:
: Here are the voltage readings on the 6A7 tube.
:
:Pins 1 & 7: 6.8 volts AC (Filament)
:Pin 2: 107.5 v DC (Plate)
:Pin 3: 43.5 volts DC (G3 and G5)
:Pin 4: 106.7 volts (G2)
:Pin 5: 2.2 V DC (G1)
:Pin 6: 2.647 volts DC (Cathode)
:Cap: -.361 v DC (G4)
:
:These seem like pretty healthy voltages to me. I don't see anything wrong there. The IF transformer is connecting B+ to the plate and the Oscillator coil is connecting B+ to to pin 4. So neither coil is open.
:
:I did notice that C17 was missing. I put it back and it might have made an improvement but not with the oscillator.
:
:Please if anyone has anymore ideas before I "attack" (very closely examine) the oscillator coil, please help.
:
:Thanks,
:
:Dave
:
::Marv,
:: My RF signal generator modulates a 400 Hz tone on the 456 Kc carrier frequency when it's set to 456 Kc. The part of the radio that the signal generator is connected to is tune to exactly tuned to 456 Kc. It can receive 456 Kc and only 456 Kc. That "station" is received and I can blast the 400 Hz tone through the speaker of the radio. If I change the RF signal generator to another frequency, then no 400 Hz tone is heard. It is as perfectly aligned as I can get it. It may not have the best adjacent channel rejection but the signal is the strongest when the signal generator is set to 456 Kc.
:: The front part of the radio is what I'm having trouble with, and NOT the 456 Kc area. The radio is not converting (moving) the received frequency to 456 Kc. I can hear 570 Kc near the low end of the band and 620 Kc near the high end of the band (I live right near the brodcast antennas for these stations). That's all it does. It absolutely refuses to oscillate under any circumstances. I have checked about all I can check. All is working and not working at the same time.
:: The trimmers you are talking about are the oscillator trimmers that can only do anything, are only active, if the oscillator is working. I can put them in any position and they do nothing. They aren't shorted. They are perfectly good but not active because the oscillator is dead.
:: C-18 is brand new. It doesn't have any problems. One end is connected to the chassis and the other end is connected to a resistor. R3. I'll double check that it's also connected to the dead oscillator coil. It's not open. It just refuses to oscillate. All 11 paper and 2 electrolytic capacitors have been replaced. The positives of the electrolytic capacitors connect to the same place and the negatives connect to two different places.
:: I am getting close to removing the oscillator coil and replacing it or rewinding this one. If only I had the specs for this one. The part number on it is: 2DT200. Maybe someone has an Emerson specs book.
::
::Thanks,
::
::Dave
::
:::Dave,
:::The oscillator has 2 trimmers in BC mode. One on the tuning cap (C-3) and the other at the rear (C-5), either of which could hamper operation if misadjusted. The one at C-3 is common to both SW and BC. Check C-18. Also, when you tested the IF, (456kHz) were you using signal levels low to moderate or high enough to blast through at any freq?
:::
:::marv
:::
::::Marv,
:::: The resistors are the correct value. I checked them. I never replaced them. I also knew that the long black capacitor looking devices were also resistors. They are all correct. The capacitors are in the correct places. Nothing has been changed.
:::: I'll check the voltage and double check for "birdies". I think I did hear them. My huge isolation transformer is getting a lot of use on this restoration.
::::
::::Thanks,
::::
::::Dave
::::
:::::Dave,
:::::In reading your 2 posts, I assume the set never worked and you re-capped and replaced bad resistors first. In this case, did you replace the parts just as they were originally installed, but did you also verify their placement via the schematic?
:::::
:::::marv
:::::
::::::Radiodoc,
:::::: I just tried that and it makes absolutely no difference whatsoever.
:::::: What do I look at next?
::::::
::::::Thanks,
::::::
:::::::Dave,
:::::::
:::::::The 98 volts is probably ok. If all else failed and as a shot in the dark, I would reverse the coil leads on the non-tuned winding between B+ and the oscillator "plate" and see what happens.
:::::::
:::::::Radiodoc
:::::::***************
:::::::
::::::::Radiodoc,
:::::::: I took out the oscillator coil and checked every connection and all are good (Perfect), no opens. I checked and cleaned the band switch several times. I replaced C9 several times. When I connect 456 Kc to it from my RF signal generator, it receives that tone perfectly. It blasts!! But it wont take what's presented to it from the antenna terminals and convert that to 456 Kc. It absolutely refuses to do that under any circumstances.
:::::::: I checked all the connections and they are perfectly perfectly perfect. The resistors are all the correct values. The solder connections have been re-done and they are nice and shiny.
:::::::: I tried 3 different 6A7 tubes and none of them make any difference.
:::::::: I checked to make sure that the tuning capacitor or trimmer have any shorts on the oscillator side and there are no shorts. When the set is on and I try to adjust the oscillator screw or short the rotor with the stator on the oscillator side it makes no difference at all. All it's doing is "TRFing". The person who owns this radio MUST have the radio working immediately. I must continue working on it until it works. What do I do next? How do I convert it to a TRF receiver?
::::::::
::::::::Thanks,
::::::::
::::::::Dave
:::::::::Radiodoc,
::::::::: B+ is 98 volts. Is that low? Shouldn't it be a little higher? I can't see any way to raise it. Filament voltage on the 6A7 is 5.3 volts.
:::::::::
:::::::::Thanks,
:::::::::
:::::::::Dave
::::::::::Radiodoc,
:::::::::: C9 is a 100 pf capacitor. I replaced it and it made absolutely no difference.
::::::::::
::::::::::Dave
:::::::::::Dave,
:::::::::::
:::::::::::If all fails, walk away for a while and then come back and check carefully all the wiring around the osc circuit for correctness and good solder joints. Did you check C9 (probably a mica)or replace it. If not may try substituting another. Voltage checks on the stage may give a clue if any are off very much.
:::::::::::
:::::::::::Radiodoc
:::::::::::***********
:::::::::::
:::::::::::
::::::::::::Hello All,
:::::::::::: I have checked everything and the oscillator absolutely refuses to work. All paper and filter capacitors have been replaced. No part of the oscillator coil is open. The resistors are good. I tried a few 6A7s and it still wont work. What to I look at next?
:::::::::::: This is an AC/DC set. There's not that much there.
::::::::::::
::::::::::::Thanks,
::::::::::::
::::::::::::Dave
This oscillator is dead, dead, dead. A transistor radio will pick up nothing from it. Also, the radio works exactly the same way whether the oscillator coil is connected to the oscillator side of the tuning capacitor or not. No difference. It absolutely refuses to oscillate even though all is connected perfectly. All components are good too (except for I believe, the oscillator coil). I have more than qadruple checked the 30K, 50K, and 300 whatever ohm resistors. They are hooked up correctly. Also, the another 100pf capacitor was tried and it makes no difference. It's still dead dead dead.
I don't quite understand what you want me to do with the B & K. But I was able to use the B & K to "tune" the radio in the CW position. The rest of the radio receives the 460 Kc perfectly. So it's ready for the oscillator/mixer circuit to work. I am getting ready to replace the oscillator coil. I think I can take one from another AC/DC set just to try it out. Can I do that? I see the that there is a B+ side (output) and the other side that connects to the oscillator side of the tuning capacitor. I think that the second I replace the oscillator coil it will work perfectly. Please correct me if I'm wrong.
The oscillator coil has two sections on it. One is the Litz wire and the other is the enameled wire.
I think that what you want me to do at the junction of c1 and R9 is to inject an oscillation to see if I can then tune the radio normally with its tuning capacitor.
Thanks,
Dave
:
:
:
:
:After reviewing your last postings info:
:My fustus “querstion” was if the radio operated in some degree of receiving stations ? via a tunable superheterodyne action / mode prior to the mass recapping of the unit ?
:
:
:
:Can we assume that C9..100 mmfd was ok and not even messed with ?
:Is cathode resistor R2 wired up ok and at its ~350 ohm value ?
:As well as the grid resistor of R1 ….50k wired properly and at its value ?
:The last item which I am sure that you did get involved with was the cathode bypass Condenser C7….05 ufd and it is OK and was reinstalled to the correct terminals…right…as that is also as critical as the 3 companion items.
:
:
:
:Looks as if the oscillator coil is on the larger ½ to ¾ in coil form and and a Litz wound unit in a tight layer…rather than the old style of enameled wire wound the full length of a long coil form. Plus, you seem to attest of its wirings continuity integrity as well as the adjunct tuning cap and its trimmer caps not being shorted out or dragging plates. Plus the additional reverting of one of the windings for a proper feed back phase check.
:Also with your BEE und KAY, you should be able to couple its input into the first grid of the mixer and at the proper injection of CW RF level, be able to swing its dial thru the 1005-2195 khc range and tune thru your stronger receptive stations in the area, with the two “TRF” stations being the powerhouses, BUT with the necessity of having to manually tune the tuning condenser in order to optimize the RF section being in resonance with them, when trying for weaker stations in bringing up received reception level..
:
:
:
:To further ease your mind about the radios oscillator sections L-C combinations , you could go to the juncture of C9 and R1 and couple in CW RF via a series / isolative ~100 pf cap and go to the same junction and tack on an anode of a 1N34 / 60 / 64 / 270 GERMANIUM diode and at its cathodes end , take a .001 cap for bypassing to ground and then meter the cathodes output via a VTVM.
:
:
:(N0…1N 914’s/4148’s/1N400oseries for this application)(Radio Shack stocks them in case you don’t have one from an oooold generation AM transistor radio chassis or from the building of a crystal set.)
:
:
:
:Then if you will power up the BEE und KAY and place in its CW mode and set the Emerson…(No power required....as this testing will be passive)…to the 1/3 lower end of the dial 700 kc ish (tuning cap ~ ¾ meshed)
:Then you tune the B & K in the ~1000-1400 range and see if the co-joined parasitic tuned oscillators circuit doesn’t give you a rising / declining reading as resonance was scanned across.
:Then, hop the radios tuning up to the higher third of the band (tuning cap ~ 1/4 meshed) and test for a like reading of a viable resonant circuit pair working at that
:frequency also.
:Thereby you have merely temp- rigged up a “po boys” grid dipper to interpret the presence of a functioning / resonating effect by the osc sections variable L-C pair and it having some degree of “Q”.
:
:
:The other alternative being that recurrent sweep Eico 460 Scope / Kluge of yours, so I think that with the former detected and metered RF , you would be much better off.
:
:
:
:Addenda:
:Noticed your new readings just at this posting time, and the bucolic local osc grid voltages reading. And have you confirmed that there is even any level oscillation by the taking of a portable xstr radios ferri-loop and placing it atop the osc coil winding and tune it off station just onto the very edge / sideband of a weaker ~1400-1740 kc AM station and then run the operating radio's tuning condenser across the bottom half of the AM band to see if even a weak heterodyning / birdie is heard on the xstr radio.
:
:Standing by for feed back
:
:
:73's de Edd
:
:
:
:
:
:
:
:
:
:
::Marv and all,
::
:: Here are the voltage readings on the 6A7 tube.
::
::Pins 1 & 7: 6.8 volts AC (Filament)
::Pin 2: 107.5 v DC (Plate)
::Pin 3: 43.5 volts DC (G3 and G5)
::Pin 4: 106.7 volts (G2)
::Pin 5: 2.2 V DC (G1)
::Pin 6: 2.647 volts DC (Cathode)
::Cap: -.361 v DC (G4)
::
::These seem like pretty healthy voltages to me. I don't see anything wrong there. The IF transformer is connecting B+ to the plate and the Oscillator coil is connecting B+ to to pin 4. So neither coil is open.
::
::I did notice that C17 was missing. I put it back and it might have made an improvement but not with the oscillator.
::
::Please if anyone has anymore ideas before I "attack" (very closely examine) the oscillator coil, please help.
::
::Thanks,
::
::Dave
::
:::Marv,
::: My RF signal generator modulates a 400 Hz tone on the 456 Kc carrier frequency when it's set to 456 Kc. The part of the radio that the signal generator is connected to is tune to exactly tuned to 456 Kc. It can receive 456 Kc and only 456 Kc. That "station" is received and I can blast the 400 Hz tone through the speaker of the radio. If I change the RF signal generator to another frequency, then no 400 Hz tone is heard. It is as perfectly aligned as I can get it. It may not have the best adjacent channel rejection but the signal is the strongest when the signal generator is set to 456 Kc.
::: The front part of the radio is what I'm having trouble with, and NOT the 456 Kc area. The radio is not converting (moving) the received frequency to 456 Kc. I can hear 570 Kc near the low end of the band and 620 Kc near the high end of the band (I live right near the brodcast antennas for these stations). That's all it does. It absolutely refuses to oscillate under any circumstances. I have checked about all I can check. All is working and not working at the same time.
::: The trimmers you are talking about are the oscillator trimmers that can only do anything, are only active, if the oscillator is working. I can put them in any position and they do nothing. They aren't shorted. They are perfectly good but not active because the oscillator is dead.
::: C-18 is brand new. It doesn't have any problems. One end is connected to the chassis and the other end is connected to a resistor. R3. I'll double check that it's also connected to the dead oscillator coil. It's not open. It just refuses to oscillate. All 11 paper and 2 electrolytic capacitors have been replaced. The positives of the electrolytic capacitors connect to the same place and the negatives connect to two different places.
::: I am getting close to removing the oscillator coil and replacing it or rewinding this one. If only I had the specs for this one. The part number on it is: 2DT200. Maybe someone has an Emerson specs book.
:::
:::Thanks,
:::
:::Dave
:::
::::Dave,
::::The oscillator has 2 trimmers in BC mode. One on the tuning cap (C-3) and the other at the rear (C-5), either of which could hamper operation if misadjusted. The one at C-3 is common to both SW and BC. Check C-18. Also, when you tested the IF, (456kHz) were you using signal levels low to moderate or high enough to blast through at any freq?
::::
::::marv
::::
:::::Marv,
::::: The resistors are the correct value. I checked them. I never replaced them. I also knew that the long black capacitor looking devices were also resistors. They are all correct. The capacitors are in the correct places. Nothing has been changed.
::::: I'll check the voltage and double check for "birdies". I think I did hear them. My huge isolation transformer is getting a lot of use on this restoration.
:::::
:::::Thanks,
:::::
:::::Dave
:::::
::::::Dave,
::::::In reading your 2 posts, I assume the set never worked and you re-capped and replaced bad resistors first. In this case, did you replace the parts just as they were originally installed, but did you also verify their placement via the schematic?
::::::
::::::marv
::::::
:::::::Radiodoc,
::::::: I just tried that and it makes absolutely no difference whatsoever.
::::::: What do I look at next?
:::::::
:::::::Thanks,
:::::::
::::::::Dave,
::::::::
::::::::The 98 volts is probably ok. If all else failed and as a shot in the dark, I would reverse the coil leads on the non-tuned winding between B+ and the oscillator "plate" and see what happens.
::::::::
::::::::Radiodoc
::::::::***************
::::::::
:::::::::Radiodoc,
::::::::: I took out the oscillator coil and checked every connection and all are good (Perfect), no opens. I checked and cleaned the band switch several times. I replaced C9 several times. When I connect 456 Kc to it from my RF signal generator, it receives that tone perfectly. It blasts!! But it wont take what's presented to it from the antenna terminals and convert that to 456 Kc. It absolutely refuses to do that under any circumstances.
::::::::: I checked all the connections and they are perfectly perfectly perfect. The resistors are all the correct values. The solder connections have been re-done and they are nice and shiny.
::::::::: I tried 3 different 6A7 tubes and none of them make any difference.
::::::::: I checked to make sure that the tuning capacitor or trimmer have any shorts on the oscillator side and there are no shorts. When the set is on and I try to adjust the oscillator screw or short the rotor with the stator on the oscillator side it makes no difference at all. All it's doing is "TRFing". The person who owns this radio MUST have the radio working immediately. I must continue working on it until it works. What do I do next? How do I convert it to a TRF receiver?
:::::::::
:::::::::Thanks,
:::::::::
:::::::::Dave
::::::::::Radiodoc,
:::::::::: B+ is 98 volts. Is that low? Shouldn't it be a little higher? I can't see any way to raise it. Filament voltage on the 6A7 is 5.3 volts.
::::::::::
::::::::::Thanks,
::::::::::
::::::::::Dave
:::::::::::Radiodoc,
::::::::::: C9 is a 100 pf capacitor. I replaced it and it made absolutely no difference.
:::::::::::
:::::::::::Dave
::::::::::::Dave,
::::::::::::
::::::::::::If all fails, walk away for a while and then come back and check carefully all the wiring around the osc circuit for correctness and good solder joints. Did you check C9 (probably a mica)or replace it. If not may try substituting another. Voltage checks on the stage may give a clue if any are off very much.
::::::::::::
::::::::::::Radiodoc
::::::::::::***********
::::::::::::
::::::::::::
:::::::::::::Hello All,
::::::::::::: I have checked everything and the oscillator absolutely refuses to work. All paper and filter capacitors have been replaced. No part of the oscillator coil is open. The resistors are good. I tried a few 6A7s and it still wont work. What to I look at next?
::::::::::::: This is an AC/DC set. There's not that much there.
:::::::::::::
:::::::::::::Thanks,
:::::::::::::
:::::::::::::Dave
That Gifs.net website doesn't exist. So all I get is a blue box with a question mark in it. I'll get you the error message as soon as my browser times out.
"Safari can’t open the page.
Safari could not open the page “http://www.gifs.net/” because the server stopped responding."
As far as I can tell that website doesn't exist.
But this website is there:
Thanks,
Dave
:Edd,
: This oscillator is dead, dead, dead. A transistor radio will pick up nothing from it. Also, the radio works exactly the same way whether the oscillator coil is connected to the oscillator side of the tuning capacitor or not. No difference. It absolutely refuses to oscillate even though all is connected perfectly. All components are good too (except for I believe, the oscillator coil). I have more than qadruple checked the 30K, 50K, and 300 whatever ohm resistors. They are hooked up correctly. Also, the another 100pf capacitor was tried and it makes no difference. It's still dead dead dead.
: I don't quite understand what you want me to do with the B & K. But I was able to use the B & K to "tune" the radio in the CW position. The rest of the radio receives the 460 Kc perfectly. So it's ready for the oscillator/mixer circuit to work. I am getting ready to replace the oscillator coil. I think I can take one from another AC/DC set just to try it out. Can I do that? I see the that there is a B+ side (output) and the other side that connects to the oscillator side of the tuning capacitor. I think that the second I replace the oscillator coil it will work perfectly. Please correct me if I'm wrong.
: The oscillator coil has two sections on it. One is the Litz wire and the other is the enameled wire.
: I think that what you want me to do at the junction of c1 and R9 is to inject an oscillation to see if I can then tune the radio normally with its tuning capacitor.
:
:Thanks,
:
:Dave
::
::
::
::
::After reviewing your last postings info:
::My fustus “querstion” was if the radio operated in some degree of receiving stations ? via a tunable superheterodyne action / mode prior to the mass recapping of the unit ?
::
::
::
::Can we assume that C9..100 mmfd was ok and not even messed with ?
::Is cathode resistor R2 wired up ok and at its ~350 ohm value ?
::As well as the grid resistor of R1 ….50k wired properly and at its value ?
::The last item which I am sure that you did get involved with was the cathode bypass Condenser C7….05 ufd and it is OK and was reinstalled to the correct terminals…right…as that is also as critical as the 3 companion items.
::
::
::
::Looks as if the oscillator coil is on the larger ½ to ¾ in coil form and and a Litz wound unit in a tight layer…rather than the old style of enameled wire wound the full length of a long coil form. Plus, you seem to attest of its wirings continuity integrity as well as the adjunct tuning cap and its trimmer caps not being shorted out or dragging plates. Plus the additional reverting of one of the windings for a proper feed back phase check.
::Also with your BEE und KAY, you should be able to couple its input into the first grid of the mixer and at the proper injection of CW RF level, be able to swing its dial thru the 1005-2195 khc range and tune thru your stronger receptive stations in the area, with the two “TRF” stations being the powerhouses, BUT with the necessity of having to manually tune the tuning condenser in order to optimize the RF section being in resonance with them, when trying for weaker stations in bringing up received reception level..
::
::
::
::To further ease your mind about the radios oscillator sections L-C combinations , you could go to the juncture of C9 and R1 and couple in CW RF via a series / isolative ~100 pf cap and go to the same junction and tack on an anode of a 1N34 / 60 / 64 / 270 GERMANIUM diode and at its cathodes end , take a .001 cap for bypassing to ground and then meter the cathodes output via a VTVM.
::
::
::(N0…1N 914’s/4148’s/1N400oseries for this application)(Radio Shack stocks them in case you don’t have one from an oooold generation AM transistor radio chassis or from the building of a crystal set.)
::
::
::
::Then if you will power up the BEE und KAY and place in its CW mode and set the Emerson…(No power required....as this testing will be passive)…to the 1/3 lower end of the dial 700 kc ish (tuning cap ~ ¾ meshed)
::Then you tune the B & K in the ~1000-1400 range and see if the co-joined parasitic tuned oscillators circuit doesn’t give you a rising / declining reading as resonance was scanned across.
::Then, hop the radios tuning up to the higher third of the band (tuning cap ~ 1/4 meshed) and test for a like reading of a viable resonant circuit pair working at that
::frequency also.
::Thereby you have merely temp- rigged up a “po boys” grid dipper to interpret the presence of a functioning / resonating effect by the osc sections variable L-C pair and it having some degree of “Q”.
::
::
::The other alternative being that recurrent sweep Eico 460 Scope / Kluge of yours, so I think that with the former detected and metered RF , you would be much better off.
::
::
::
::Addenda:
::Noticed your new readings just at this posting time, and the bucolic local osc grid voltages reading. And have you confirmed that there is even any level oscillation by the taking of a portable xstr radios ferri-loop and placing it atop the osc coil winding and tune it off station just onto the very edge / sideband of a weaker ~1400-1740 kc AM station and then run the operating radio's tuning condenser across the bottom half of the AM band to see if even a weak heterodyning / birdie is heard on the xstr radio.
::
::Standing by for feed back
::
::
::73's de Edd
::
::
::
::
::
::
::
::
::
::
:::Marv and all,
:::
::: Here are the voltage readings on the 6A7 tube.
:::
:::Pins 1 & 7: 6.8 volts AC (Filament)
:::Pin 2: 107.5 v DC (Plate)
:::Pin 3: 43.5 volts DC (G3 and G5)
:::Pin 4: 106.7 volts (G2)
:::Pin 5: 2.2 V DC (G1)
:::Pin 6: 2.647 volts DC (Cathode)
:::Cap: -.361 v DC (G4)
:::
:::These seem like pretty healthy voltages to me. I don't see anything wrong there. The IF transformer is connecting B+ to the plate and the Oscillator coil is connecting B+ to to pin 4. So neither coil is open.
:::
:::I did notice that C17 was missing. I put it back and it might have made an improvement but not with the oscillator.
:::
:::Please if anyone has anymore ideas before I "attack" (very closely examine) the oscillator coil, please help.
:::
:::Thanks,
:::
:::Dave
:::
::::Marv,
:::: My RF signal generator modulates a 400 Hz tone on the 456 Kc carrier frequency when it's set to 456 Kc. The part of the radio that the signal generator is connected to is tune to exactly tuned to 456 Kc. It can receive 456 Kc and only 456 Kc. That "station" is received and I can blast the 400 Hz tone through the speaker of the radio. If I change the RF signal generator to another frequency, then no 400 Hz tone is heard. It is as perfectly aligned as I can get it. It may not have the best adjacent channel rejection but the signal is the strongest when the signal generator is set to 456 Kc.
:::: The front part of the radio is what I'm having trouble with, and NOT the 456 Kc area. The radio is not converting (moving) the received frequency to 456 Kc. I can hear 570 Kc near the low end of the band and 620 Kc near the high end of the band (I live right near the brodcast antennas for these stations). That's all it does. It absolutely refuses to oscillate under any circumstances. I have checked about all I can check. All is working and not working at the same time.
:::: The trimmers you are talking about are the oscillator trimmers that can only do anything, are only active, if the oscillator is working. I can put them in any position and they do nothing. They aren't shorted. They are perfectly good but not active because the oscillator is dead.
:::: C-18 is brand new. It doesn't have any problems. One end is connected to the chassis and the other end is connected to a resistor. R3. I'll double check that it's also connected to the dead oscillator coil. It's not open. It just refuses to oscillate. All 11 paper and 2 electrolytic capacitors have been replaced. The positives of the electrolytic capacitors connect to the same place and the negatives connect to two different places.
:::: I am getting close to removing the oscillator coil and replacing it or rewinding this one. If only I had the specs for this one. The part number on it is: 2DT200. Maybe someone has an Emerson specs book.
::::
::::Thanks,
::::
::::Dave
::::
:::::Dave,
:::::The oscillator has 2 trimmers in BC mode. One on the tuning cap (C-3) and the other at the rear (C-5), either of which could hamper operation if misadjusted. The one at C-3 is common to both SW and BC. Check C-18. Also, when you tested the IF, (456kHz) were you using signal levels low to moderate or high enough to blast through at any freq?
:::::
:::::marv
:::::
::::::Marv,
:::::: The resistors are the correct value. I checked them. I never replaced them. I also knew that the long black capacitor looking devices were also resistors. They are all correct. The capacitors are in the correct places. Nothing has been changed.
:::::: I'll check the voltage and double check for "birdies". I think I did hear them. My huge isolation transformer is getting a lot of use on this restoration.
::::::
::::::Thanks,
::::::
::::::Dave
::::::
:::::::Dave,
:::::::In reading your 2 posts, I assume the set never worked and you re-capped and replaced bad resistors first. In this case, did you replace the parts just as they were originally installed, but did you also verify their placement via the schematic?
:::::::
:::::::marv
:::::::
::::::::Radiodoc,
:::::::: I just tried that and it makes absolutely no difference whatsoever.
:::::::: What do I look at next?
::::::::
::::::::Thanks,
::::::::
:::::::::Dave,
:::::::::
:::::::::The 98 volts is probably ok. If all else failed and as a shot in the dark, I would reverse the coil leads on the non-tuned winding between B+ and the oscillator "plate" and see what happens.
:::::::::
:::::::::Radiodoc
:::::::::***************
:::::::::
::::::::::Radiodoc,
:::::::::: I took out the oscillator coil and checked every connection and all are good (Perfect), no opens. I checked and cleaned the band switch several times. I replaced C9 several times. When I connect 456 Kc to it from my RF signal generator, it receives that tone perfectly. It blasts!! But it wont take what's presented to it from the antenna terminals and convert that to 456 Kc. It absolutely refuses to do that under any circumstances.
:::::::::: I checked all the connections and they are perfectly perfectly perfect. The resistors are all the correct values. The solder connections have been re-done and they are nice and shiny.
:::::::::: I tried 3 different 6A7 tubes and none of them make any difference.
:::::::::: I checked to make sure that the tuning capacitor or trimmer have any shorts on the oscillator side and there are no shorts. When the set is on and I try to adjust the oscillator screw or short the rotor with the stator on the oscillator side it makes no difference at all. All it's doing is "TRFing". The person who owns this radio MUST have the radio working immediately. I must continue working on it until it works. What do I do next? How do I convert it to a TRF receiver?
::::::::::
::::::::::Thanks,
::::::::::
::::::::::Dave
:::::::::::Radiodoc,
::::::::::: B+ is 98 volts. Is that low? Shouldn't it be a little higher? I can't see any way to raise it. Filament voltage on the 6A7 is 5.3 volts.
:::::::::::
:::::::::::Thanks,
:::::::::::
:::::::::::Dave
::::::::::::Radiodoc,
:::::::::::: C9 is a 100 pf capacitor. I replaced it and it made absolutely no difference.
::::::::::::
::::::::::::Dave
:::::::::::::Dave,
:::::::::::::
:::::::::::::If all fails, walk away for a while and then come back and check carefully all the wiring around the osc circuit for correctness and good solder joints. Did you check C9 (probably a mica)or replace it. If not may try substituting another. Voltage checks on the stage may give a clue if any are off very much.
:::::::::::::
:::::::::::::Radiodoc
:::::::::::::***********
:::::::::::::
:::::::::::::
::::::::::::::Hello All,
:::::::::::::: I have checked everything and the oscillator absolutely refuses to work. All paper and filter capacitors have been replaced. No part of the oscillator coil is open. The resistors are good. I tried a few 6A7s and it still wont work. What to I look at next?
:::::::::::::: This is an AC/DC set. There's not that much there.
::::::::::::::
::::::::::::::Thanks,
::::::::::::::
::::::::::::::Dave
You have eliminated almost everything. There is one remaining item though. Are you sure the socket/tube pin connections are firm?
marv
:Edd,
: This oscillator is dead, dead, dead. A transistor radio will pick up nothing from it. Also, the radio works exactly the same way whether the oscillator coil is connected to the oscillator side of the tuning capacitor or not. No difference. It absolutely refuses to oscillate even though all is connected perfectly. All components are good too (except for I believe, the oscillator coil). I have more than qadruple checked the 30K, 50K, and 300 whatever ohm resistors. They are hooked up correctly. Also, the another 100pf capacitor was tried and it makes no difference. It's still dead dead dead.
: I don't quite understand what you want me to do with the B & K. But I was able to use the B & K to "tune" the radio in the CW position. The rest of the radio receives the 460 Kc perfectly. So it's ready for the oscillator/mixer circuit to work. I am getting ready to replace the oscillator coil. I think I can take one from another AC/DC set just to try it out. Can I do that? I see the that there is a B+ side (output) and the other side that connects to the oscillator side of the tuning capacitor. I think that the second I replace the oscillator coil it will work perfectly. Please correct me if I'm wrong.
: The oscillator coil has two sections on it. One is the Litz wire and the other is the enameled wire.
: I think that what you want me to do at the junction of c1 and R9 is to inject an oscillation to see if I can then tune the radio normally with its tuning capacitor.
:
:Thanks,
:
:Dave
::
::
::
::
::After reviewing your last postings info:
::My fustus “querstion” was if the radio operated in some degree of receiving stations ? via a tunable superheterodyne action / mode prior to the mass recapping of the unit ?
::
::
::
::Can we assume that C9..100 mmfd was ok and not even messed with ?
::Is cathode resistor R2 wired up ok and at its ~350 ohm value ?
::As well as the grid resistor of R1 ….50k wired properly and at its value ?
::The last item which I am sure that you did get involved with was the cathode bypass Condenser C7….05 ufd and it is OK and was reinstalled to the correct terminals…right…as that is also as critical as the 3 companion items.
::
::
::
::Looks as if the oscillator coil is on the larger ½ to ¾ in coil form and and a Litz wound unit in a tight layer…rather than the old style of enameled wire wound the full length of a long coil form. Plus, you seem to attest of its wirings continuity integrity as well as the adjunct tuning cap and its trimmer caps not being shorted out or dragging plates. Plus the additional reverting of one of the windings for a proper feed back phase check.
::Also with your BEE und KAY, you should be able to couple its input into the first grid of the mixer and at the proper injection of CW RF level, be able to swing its dial thru the 1005-2195 khc range and tune thru your stronger receptive stations in the area, with the two “TRF” stations being the powerhouses, BUT with the necessity of having to manually tune the tuning condenser in order to optimize the RF section being in resonance with them, when trying for weaker stations in bringing up received reception level..
::
::
::
::To further ease your mind about the radios oscillator sections L-C combinations , you could go to the juncture of C9 and R1 and couple in CW RF via a series / isolative ~100 pf cap and go to the same junction and tack on an anode of a 1N34 / 60 / 64 / 270 GERMANIUM diode and at its cathodes end , take a .001 cap for bypassing to ground and then meter the cathodes output via a VTVM.
::
::
::(N0…1N 914’s/4148’s/1N400oseries for this application)(Radio Shack stocks them in case you don’t have one from an oooold generation AM transistor radio chassis or from the building of a crystal set.)
::
::
::
::Then if you will power up the BEE und KAY and place in its CW mode and set the Emerson…(No power required....as this testing will be passive)…to the 1/3 lower end of the dial 700 kc ish (tuning cap ~ ¾ meshed)
::Then you tune the B & K in the ~1000-1400 range and see if the co-joined parasitic tuned oscillators circuit doesn’t give you a rising / declining reading as resonance was scanned across.
::Then, hop the radios tuning up to the higher third of the band (tuning cap ~ 1/4 meshed) and test for a like reading of a viable resonant circuit pair working at that
::frequency also.
::Thereby you have merely temp- rigged up a “po boys” grid dipper to interpret the presence of a functioning / resonating effect by the osc sections variable L-C pair and it having some degree of “Q”.
::
::
::The other alternative being that recurrent sweep Eico 460 Scope / Kluge of yours, so I think that with the former detected and metered RF , you would be much better off.
::
::
::
::Addenda:
::Noticed your new readings just at this posting time, and the bucolic local osc grid voltages reading. And have you confirmed that there is even any level oscillation by the taking of a portable xstr radios ferri-loop and placing it atop the osc coil winding and tune it off station just onto the very edge / sideband of a weaker ~1400-1740 kc AM station and then run the operating radio's tuning condenser across the bottom half of the AM band to see if even a weak heterodyning / birdie is heard on the xstr radio.
::
::Standing by for feed back
::
::
::73's de Edd
::
::
::
::
::
::
::
::
::
::
:::Marv and all,
:::
::: Here are the voltage readings on the 6A7 tube.
:::
:::Pins 1 & 7: 6.8 volts AC (Filament)
:::Pin 2: 107.5 v DC (Plate)
:::Pin 3: 43.5 volts DC (G3 and G5)
:::Pin 4: 106.7 volts (G2)
:::Pin 5: 2.2 V DC (G1)
:::Pin 6: 2.647 volts DC (Cathode)
:::Cap: -.361 v DC (G4)
:::
:::These seem like pretty healthy voltages to me. I don't see anything wrong there. The IF transformer is connecting B+ to the plate and the Oscillator coil is connecting B+ to to pin 4. So neither coil is open.
:::
:::I did notice that C17 was missing. I put it back and it might have made an improvement but not with the oscillator.
:::
:::Please if anyone has anymore ideas before I "attack" (very closely examine) the oscillator coil, please help.
:::
:::Thanks,
:::
:::Dave
:::
::::Marv,
:::: My RF signal generator modulates a 400 Hz tone on the 456 Kc carrier frequency when it's set to 456 Kc. The part of the radio that the signal generator is connected to is tune to exactly tuned to 456 Kc. It can receive 456 Kc and only 456 Kc. That "station" is received and I can blast the 400 Hz tone through the speaker of the radio. If I change the RF signal generator to another frequency, then no 400 Hz tone is heard. It is as perfectly aligned as I can get it. It may not have the best adjacent channel rejection but the signal is the strongest when the signal generator is set to 456 Kc.
:::: The front part of the radio is what I'm having trouble with, and NOT the 456 Kc area. The radio is not converting (moving) the received frequency to 456 Kc. I can hear 570 Kc near the low end of the band and 620 Kc near the high end of the band (I live right near the brodcast antennas for these stations). That's all it does. It absolutely refuses to oscillate under any circumstances. I have checked about all I can check. All is working and not working at the same time.
:::: The trimmers you are talking about are the oscillator trimmers that can only do anything, are only active, if the oscillator is working. I can put them in any position and they do nothing. They aren't shorted. They are perfectly good but not active because the oscillator is dead.
:::: C-18 is brand new. It doesn't have any problems. One end is connected to the chassis and the other end is connected to a resistor. R3. I'll double check that it's also connected to the dead oscillator coil. It's not open. It just refuses to oscillate. All 11 paper and 2 electrolytic capacitors have been replaced. The positives of the electrolytic capacitors connect to the same place and the negatives connect to two different places.
:::: I am getting close to removing the oscillator coil and replacing it or rewinding this one. If only I had the specs for this one. The part number on it is: 2DT200. Maybe someone has an Emerson specs book.
::::
::::Thanks,
::::
::::Dave
::::
:::::Dave,
:::::The oscillator has 2 trimmers in BC mode. One on the tuning cap (C-3) and the other at the rear (C-5), either of which could hamper operation if misadjusted. The one at C-3 is common to both SW and BC. Check C-18. Also, when you tested the IF, (456kHz) were you using signal levels low to moderate or high enough to blast through at any freq?
:::::
:::::marv
:::::
::::::Marv,
:::::: The resistors are the correct value. I checked them. I never replaced them. I also knew that the long black capacitor looking devices were also resistors. They are all correct. The capacitors are in the correct places. Nothing has been changed.
:::::: I'll check the voltage and double check for "birdies". I think I did hear them. My huge isolation transformer is getting a lot of use on this restoration.
::::::
::::::Thanks,
::::::
::::::Dave
::::::
:::::::Dave,
:::::::In reading your 2 posts, I assume the set never worked and you re-capped and replaced bad resistors first. In this case, did you replace the parts just as they were originally installed, but did you also verify their placement via the schematic?
:::::::
:::::::marv
:::::::
::::::::Radiodoc,
:::::::: I just tried that and it makes absolutely no difference whatsoever.
:::::::: What do I look at next?
::::::::
::::::::Thanks,
::::::::
:::::::::Dave,
:::::::::
:::::::::The 98 volts is probably ok. If all else failed and as a shot in the dark, I would reverse the coil leads on the non-tuned winding between B+ and the oscillator "plate" and see what happens.
:::::::::
:::::::::Radiodoc
:::::::::***************
:::::::::
::::::::::Radiodoc,
:::::::::: I took out the oscillator coil and checked every connection and all are good (Perfect), no opens. I checked and cleaned the band switch several times. I replaced C9 several times. When I connect 456 Kc to it from my RF signal generator, it receives that tone perfectly. It blasts!! But it wont take what's presented to it from the antenna terminals and convert that to 456 Kc. It absolutely refuses to do that under any circumstances.
:::::::::: I checked all the connections and they are perfectly perfectly perfect. The resistors are all the correct values. The solder connections have been re-done and they are nice and shiny.
:::::::::: I tried 3 different 6A7 tubes and none of them make any difference.
:::::::::: I checked to make sure that the tuning capacitor or trimmer have any shorts on the oscillator side and there are no shorts. When the set is on and I try to adjust the oscillator screw or short the rotor with the stator on the oscillator side it makes no difference at all. All it's doing is "TRFing". The person who owns this radio MUST have the radio working immediately. I must continue working on it until it works. What do I do next? How do I convert it to a TRF receiver?
::::::::::
::::::::::Thanks,
::::::::::
::::::::::Dave
:::::::::::Radiodoc,
::::::::::: B+ is 98 volts. Is that low? Shouldn't it be a little higher? I can't see any way to raise it. Filament voltage on the 6A7 is 5.3 volts.
:::::::::::
:::::::::::Thanks,
:::::::::::
:::::::::::Dave
::::::::::::Radiodoc,
:::::::::::: C9 is a 100 pf capacitor. I replaced it and it made absolutely no difference.
::::::::::::
::::::::::::Dave
:::::::::::::Dave,
:::::::::::::
:::::::::::::If all fails, walk away for a while and then come back and check carefully all the wiring around the osc circuit for correctness and good solder joints. Did you check C9 (probably a mica)or replace it. If not may try substituting another. Voltage checks on the stage may give a clue if any are off very much.
:::::::::::::
:::::::::::::Radiodoc
:::::::::::::***********
:::::::::::::
:::::::::::::
::::::::::::::Hello All,
:::::::::::::: I have checked everything and the oscillator absolutely refuses to work. All paper and filter capacitors have been replaced. No part of the oscillator coil is open. The resistors are good. I tried a few 6A7s and it still wont work. What to I look at next?
:::::::::::::: This is an AC/DC set. There's not that much there.
::::::::::::::
::::::::::::::Thanks,
::::::::::::::
::::::::::::::Dave
Yes they are. I measure the pin and the contact and I get the same reading from both. But I'll double check.
Thanks,
Dave
:Dave,
:You have eliminated almost everything. There is one remaining item though. Are you sure the socket/tube pin connections are firm?
:
:marv
:
::Edd,
:: This oscillator is dead, dead, dead. A transistor radio will pick up nothing from it. Also, the radio works exactly the same way whether the oscillator coil is connected to the oscillator side of the tuning capacitor or not. No difference. It absolutely refuses to oscillate even though all is connected perfectly. All components are good too (except for I believe, the oscillator coil). I have more than qadruple checked the 30K, 50K, and 300 whatever ohm resistors. They are hooked up correctly. Also, the another 100pf capacitor was tried and it makes no difference. It's still dead dead dead.
:: I don't quite understand what you want me to do with the B & K. But I was able to use the B & K to "tune" the radio in the CW position. The rest of the radio receives the 460 Kc perfectly. So it's ready for the oscillator/mixer circuit to work. I am getting ready to replace the oscillator coil. I think I can take one from another AC/DC set just to try it out. Can I do that? I see the that there is a B+ side (output) and the other side that connects to the oscillator side of the tuning capacitor. I think that the second I replace the oscillator coil it will work perfectly. Please correct me if I'm wrong.
:: The oscillator coil has two sections on it. One is the Litz wire and the other is the enameled wire.
:: I think that what you want me to do at the junction of c1 and R9 is to inject an oscillation to see if I can then tune the radio normally with its tuning capacitor.
::
::Thanks,
::
::Dave
:::
:::
:::
:::
:::After reviewing your last postings info:
:::My fustus “querstion” was if the radio operated in some degree of receiving stations ? via a tunable superheterodyne action / mode prior to the mass recapping of the unit ?
:::
:::
:::
:::Can we assume that C9..100 mmfd was ok and not even messed with ?
:::Is cathode resistor R2 wired up ok and at its ~350 ohm value ?
:::As well as the grid resistor of R1 ….50k wired properly and at its value ?
:::The last item which I am sure that you did get involved with was the cathode bypass Condenser C7….05 ufd and it is OK and was reinstalled to the correct terminals…right…as that is also as critical as the 3 companion items.
:::
:::
:::
:::Looks as if the oscillator coil is on the larger ½ to ¾ in coil form and and a Litz wound unit in a tight layer…rather than the old style of enameled wire wound the full length of a long coil form. Plus, you seem to attest of its wirings continuity integrity as well as the adjunct tuning cap and its trimmer caps not being shorted out or dragging plates. Plus the additional reverting of one of the windings for a proper feed back phase check.
:::Also with your BEE und KAY, you should be able to couple its input into the first grid of the mixer and at the proper injection of CW RF level, be able to swing its dial thru the 1005-2195 khc range and tune thru your stronger receptive stations in the area, with the two “TRF” stations being the powerhouses, BUT with the necessity of having to manually tune the tuning condenser in order to optimize the RF section being in resonance with them, when trying for weaker stations in bringing up received reception level..
:::
:::
:::
:::To further ease your mind about the radios oscillator sections L-C combinations , you could go to the juncture of C9 and R1 and couple in CW RF via a series / isolative ~100 pf cap and go to the same junction and tack on an anode of a 1N34 / 60 / 64 / 270 GERMANIUM diode and at its cathodes end , take a .001 cap for bypassing to ground and then meter the cathodes output via a VTVM.
:::
:::
:::(N0…1N 914’s/4148’s/1N400oseries for this application)(Radio Shack stocks them in case you don’t have one from an oooold generation AM transistor radio chassis or from the building of a crystal set.)
:::
:::
:::
:::Then if you will power up the BEE und KAY and place in its CW mode and set the Emerson…(No power required....as this testing will be passive)…to the 1/3 lower end of the dial 700 kc ish (tuning cap ~ ¾ meshed)
:::Then you tune the B & K in the ~1000-1400 range and see if the co-joined parasitic tuned oscillators circuit doesn’t give you a rising / declining reading as resonance was scanned across.
:::Then, hop the radios tuning up to the higher third of the band (tuning cap ~ 1/4 meshed) and test for a like reading of a viable resonant circuit pair working at that
:::frequency also.
:::Thereby you have merely temp- rigged up a “po boys” grid dipper to interpret the presence of a functioning / resonating effect by the osc sections variable L-C pair and it having some degree of “Q”.
:::
:::
:::The other alternative being that recurrent sweep Eico 460 Scope / Kluge of yours, so I think that with the former detected and metered RF , you would be much better off.
:::
:::
:::
:::Addenda:
:::Noticed your new readings just at this posting time, and the bucolic local osc grid voltages reading. And have you confirmed that there is even any level oscillation by the taking of a portable xstr radios ferri-loop and placing it atop the osc coil winding and tune it off station just onto the very edge / sideband of a weaker ~1400-1740 kc AM station and then run the operating radio's tuning condenser across the bottom half of the AM band to see if even a weak heterodyning / birdie is heard on the xstr radio.
:::
:::Standing by for feed back
:::
:::
:::73's de Edd
:::
:::
:::
:::
:::
:::
:::
:::
:::
:::
::::Marv and all,
::::
:::: Here are the voltage readings on the 6A7 tube.
::::
::::Pins 1 & 7: 6.8 volts AC (Filament)
::::Pin 2: 107.5 v DC (Plate)
::::Pin 3: 43.5 volts DC (G3 and G5)
::::Pin 4: 106.7 volts (G2)
::::Pin 5: 2.2 V DC (G1)
::::Pin 6: 2.647 volts DC (Cathode)
::::Cap: -.361 v DC (G4)
::::
::::These seem like pretty healthy voltages to me. I don't see anything wrong there. The IF transformer is connecting B+ to the plate and the Oscillator coil is connecting B+ to to pin 4. So neither coil is open.
::::
::::I did notice that C17 was missing. I put it back and it might have made an improvement but not with the oscillator.
::::
::::Please if anyone has anymore ideas before I "attack" (very closely examine) the oscillator coil, please help.
::::
::::Thanks,
::::
::::Dave
::::
:::::Marv,
::::: My RF signal generator modulates a 400 Hz tone on the 456 Kc carrier frequency when it's set to 456 Kc. The part of the radio that the signal generator is connected to is tune to exactly tuned to 456 Kc. It can receive 456 Kc and only 456 Kc. That "station" is received and I can blast the 400 Hz tone through the speaker of the radio. If I change the RF signal generator to another frequency, then no 400 Hz tone is heard. It is as perfectly aligned as I can get it. It may not have the best adjacent channel rejection but the signal is the strongest when the signal generator is set to 456 Kc.
::::: The front part of the radio is what I'm having trouble with, and NOT the 456 Kc area. The radio is not converting (moving) the received frequency to 456 Kc. I can hear 570 Kc near the low end of the band and 620 Kc near the high end of the band (I live right near the brodcast antennas for these stations). That's all it does. It absolutely refuses to oscillate under any circumstances. I have checked about all I can check. All is working and not working at the same time.
::::: The trimmers you are talking about are the oscillator trimmers that can only do anything, are only active, if the oscillator is working. I can put them in any position and they do nothing. They aren't shorted. They are perfectly good but not active because the oscillator is dead.
::::: C-18 is brand new. It doesn't have any problems. One end is connected to the chassis and the other end is connected to a resistor. R3. I'll double check that it's also connected to the dead oscillator coil. It's not open. It just refuses to oscillate. All 11 paper and 2 electrolytic capacitors have been replaced. The positives of the electrolytic capacitors connect to the same place and the negatives connect to two different places.
::::: I am getting close to removing the oscillator coil and replacing it or rewinding this one. If only I had the specs for this one. The part number on it is: 2DT200. Maybe someone has an Emerson specs book.
:::::
:::::Thanks,
:::::
:::::Dave
:::::
::::::Dave,
::::::The oscillator has 2 trimmers in BC mode. One on the tuning cap (C-3) and the other at the rear (C-5), either of which could hamper operation if misadjusted. The one at C-3 is common to both SW and BC. Check C-18. Also, when you tested the IF, (456kHz) were you using signal levels low to moderate or high enough to blast through at any freq?
::::::
::::::marv
::::::
:::::::Marv,
::::::: The resistors are the correct value. I checked them. I never replaced them. I also knew that the long black capacitor looking devices were also resistors. They are all correct. The capacitors are in the correct places. Nothing has been changed.
::::::: I'll check the voltage and double check for "birdies". I think I did hear them. My huge isolation transformer is getting a lot of use on this restoration.
:::::::
:::::::Thanks,
:::::::
:::::::Dave
:::::::
::::::::Dave,
::::::::In reading your 2 posts, I assume the set never worked and you re-capped and replaced bad resistors first. In this case, did you replace the parts just as they were originally installed, but did you also verify their placement via the schematic?
::::::::
::::::::marv
::::::::
:::::::::Radiodoc,
::::::::: I just tried that and it makes absolutely no difference whatsoever.
::::::::: What do I look at next?
:::::::::
:::::::::Thanks,
:::::::::
::::::::::Dave,
::::::::::
::::::::::The 98 volts is probably ok. If all else failed and as a shot in the dark, I would reverse the coil leads on the non-tuned winding between B+ and the oscillator "plate" and see what happens.
::::::::::
::::::::::Radiodoc
::::::::::***************
::::::::::
:::::::::::Radiodoc,
::::::::::: I took out the oscillator coil and checked every connection and all are good (Perfect), no opens. I checked and cleaned the band switch several times. I replaced C9 several times. When I connect 456 Kc to it from my RF signal generator, it receives that tone perfectly. It blasts!! But it wont take what's presented to it from the antenna terminals and convert that to 456 Kc. It absolutely refuses to do that under any circumstances.
::::::::::: I checked all the connections and they are perfectly perfectly perfect. The resistors are all the correct values. The solder connections have been re-done and they are nice and shiny.
::::::::::: I tried 3 different 6A7 tubes and none of them make any difference.
::::::::::: I checked to make sure that the tuning capacitor or trimmer have any shorts on the oscillator side and there are no shorts. When the set is on and I try to adjust the oscillator screw or short the rotor with the stator on the oscillator side it makes no difference at all. All it's doing is "TRFing". The person who owns this radio MUST have the radio working immediately. I must continue working on it until it works. What do I do next? How do I convert it to a TRF receiver?
:::::::::::
:::::::::::Thanks,
:::::::::::
:::::::::::Dave
::::::::::::Radiodoc,
:::::::::::: B+ is 98 volts. Is that low? Shouldn't it be a little higher? I can't see any way to raise it. Filament voltage on the 6A7 is 5.3 volts.
::::::::::::
::::::::::::Thanks,
::::::::::::
::::::::::::Dave
:::::::::::::Radiodoc,
::::::::::::: C9 is a 100 pf capacitor. I replaced it and it made absolutely no difference.
:::::::::::::
:::::::::::::Dave
::::::::::::::Dave,
::::::::::::::
::::::::::::::If all fails, walk away for a while and then come back and check carefully all the wiring around the osc circuit for correctness and good solder joints. Did you check C9 (probably a mica)or replace it. If not may try substituting another. Voltage checks on the stage may give a clue if any are off very much.
::::::::::::::
::::::::::::::Radiodoc
::::::::::::::***********
::::::::::::::
::::::::::::::
:::::::::::::::Hello All,
::::::::::::::: I have checked everything and the oscillator absolutely refuses to work. All paper and filter capacitors have been replaced. No part of the oscillator coil is open. The resistors are good. I tried a few 6A7s and it still wont work. What to I look at next?
::::::::::::::: This is an AC/DC set. There's not that much there.
:::::::::::::::
:::::::::::::::Thanks,
:::::::::::::::
:::::::::::::::Dave
The connections and the voltages are quite good. But it still wont oscillate. It works and absolutely refuses to work all at the same time.
Thanks,
Dave
:Marv,
: Yes they are. I measure the pin and the contact and I get the same reading from both. But I'll double check.
:
:Thanks,
:
:Dave
::Dave,
::You have eliminated almost everything. There is one remaining item though. Are you sure the socket/tube pin connections are firm?
::
::marv
::
:::Edd,
::: This oscillator is dead, dead, dead. A transistor radio will pick up nothing from it. Also, the radio works exactly the same way whether the oscillator coil is connected to the oscillator side of the tuning capacitor or not. No difference. It absolutely refuses to oscillate even though all is connected perfectly. All components are good too (except for I believe, the oscillator coil). I have more than qadruple checked the 30K, 50K, and 300 whatever ohm resistors. They are hooked up correctly. Also, the another 100pf capacitor was tried and it makes no difference. It's still dead dead dead.
::: I don't quite understand what you want me to do with the B & K. But I was able to use the B & K to "tune" the radio in the CW position. The rest of the radio receives the 460 Kc perfectly. So it's ready for the oscillator/mixer circuit to work. I am getting ready to replace the oscillator coil. I think I can take one from another AC/DC set just to try it out. Can I do that? I see the that there is a B+ side (output) and the other side that connects to the oscillator side of the tuning capacitor. I think that the second I replace the oscillator coil it will work perfectly. Please correct me if I'm wrong.
::: The oscillator coil has two sections on it. One is the Litz wire and the other is the enameled wire.
::: I think that what you want me to do at the junction of c1 and R9 is to inject an oscillation to see if I can then tune the radio normally with its tuning capacitor.
:::
:::Thanks,
:::
:::Dave
::::
::::
::::
::::
::::After reviewing your last postings info:
::::My fustus “querstion” was if the radio operated in some degree of receiving stations ? via a tunable superheterodyne action / mode prior to the mass recapping of the unit ?
::::
::::
::::
::::Can we assume that C9..100 mmfd was ok and not even messed with ?
::::Is cathode resistor R2 wired up ok and at its ~350 ohm value ?
::::As well as the grid resistor of R1 ….50k wired properly and at its value ?
::::The last item which I am sure that you did get involved with was the cathode bypass Condenser C7….05 ufd and it is OK and was reinstalled to the correct terminals…right…as that is also as critical as the 3 companion items.
::::
::::
::::
::::Looks as if the oscillator coil is on the larger ½ to ¾ in coil form and and a Litz wound unit in a tight layer…rather than the old style of enameled wire wound the full length of a long coil form. Plus, you seem to attest of its wirings continuity integrity as well as the adjunct tuning cap and its trimmer caps not being shorted out or dragging plates. Plus the additional reverting of one of the windings for a proper feed back phase check.
::::Also with your BEE und KAY, you should be able to couple its input into the first grid of the mixer and at the proper injection of CW RF level, be able to swing its dial thru the 1005-2195 khc range and tune thru your stronger receptive stations in the area, with the two “TRF” stations being the powerhouses, BUT with the necessity of having to manually tune the tuning condenser in order to optimize the RF section being in resonance with them, when trying for weaker stations in bringing up received reception level..
::::
::::
::::
::::To further ease your mind about the radios oscillator sections L-C combinations , you could go to the juncture of C9 and R1 and couple in CW RF via a series / isolative ~100 pf cap and go to the same junction and tack on an anode of a 1N34 / 60 / 64 / 270 GERMANIUM diode and at its cathodes end , take a .001 cap for bypassing to ground and then meter the cathodes output via a VTVM.
::::
::::
::::(N0…1N 914’s/4148’s/1N400oseries for this application)(Radio Shack stocks them in case you don’t have one from an oooold generation AM transistor radio chassis or from the building of a crystal set.)
::::
::::
::::
::::Then if you will power up the BEE und KAY and place in its CW mode and set the Emerson…(No power required....as this testing will be passive)…to the 1/3 lower end of the dial 700 kc ish (tuning cap ~ ¾ meshed)
::::Then you tune the B & K in the ~1000-1400 range and see if the co-joined parasitic tuned oscillators circuit doesn’t give you a rising / declining reading as resonance was scanned across.
::::Then, hop the radios tuning up to the higher third of the band (tuning cap ~ 1/4 meshed) and test for a like reading of a viable resonant circuit pair working at that
::::frequency also.
::::Thereby you have merely temp- rigged up a “po boys” grid dipper to interpret the presence of a functioning / resonating effect by the osc sections variable L-C pair and it having some degree of “Q”.
::::
::::
::::The other alternative being that recurrent sweep Eico 460 Scope / Kluge of yours, so I think that with the former detected and metered RF , you would be much better off.
::::
::::
::::
::::Addenda:
::::Noticed your new readings just at this posting time, and the bucolic local osc grid voltages reading. And have you confirmed that there is even any level oscillation by the taking of a portable xstr radios ferri-loop and placing it atop the osc coil winding and tune it off station just onto the very edge / sideband of a weaker ~1400-1740 kc AM station and then run the operating radio's tuning condenser across the bottom half of the AM band to see if even a weak heterodyning / birdie is heard on the xstr radio.
::::
::::Standing by for feed back
::::
::::
::::73's de Edd
::::
::::
::::
::::
::::
::::
::::
::::
::::
::::
:::::Marv and all,
:::::
::::: Here are the voltage readings on the 6A7 tube.
:::::
:::::Pins 1 & 7: 6.8 volts AC (Filament)
:::::Pin 2: 107.5 v DC (Plate)
:::::Pin 3: 43.5 volts DC (G3 and G5)
:::::Pin 4: 106.7 volts (G2)
:::::Pin 5: 2.2 V DC (G1)
:::::Pin 6: 2.647 volts DC (Cathode)
:::::Cap: -.361 v DC (G4)
:::::
:::::These seem like pretty healthy voltages to me. I don't see anything wrong there. The IF transformer is connecting B+ to the plate and the Oscillator coil is connecting B+ to to pin 4. So neither coil is open.
:::::
:::::I did notice that C17 was missing. I put it back and it might have made an improvement but not with the oscillator.
:::::
:::::Please if anyone has anymore ideas before I "attack" (very closely examine) the oscillator coil, please help.
:::::
:::::Thanks,
:::::
:::::Dave
:::::
::::::Marv,
:::::: My RF signal generator modulates a 400 Hz tone on the 456 Kc carrier frequency when it's set to 456 Kc. The part of the radio that the signal generator is connected to is tune to exactly tuned to 456 Kc. It can receive 456 Kc and only 456 Kc. That "station" is received and I can blast the 400 Hz tone through the speaker of the radio. If I change the RF signal generator to another frequency, then no 400 Hz tone is heard. It is as perfectly aligned as I can get it. It may not have the best adjacent channel rejection but the signal is the strongest when the signal generator is set to 456 Kc.
:::::: The front part of the radio is what I'm having trouble with, and NOT the 456 Kc area. The radio is not converting (moving) the received frequency to 456 Kc. I can hear 570 Kc near the low end of the band and 620 Kc near the high end of the band (I live right near the brodcast antennas for these stations). That's all it does. It absolutely refuses to oscillate under any circumstances. I have checked about all I can check. All is working and not working at the same time.
:::::: The trimmers you are talking about are the oscillator trimmers that can only do anything, are only active, if the oscillator is working. I can put them in any position and they do nothing. They aren't shorted. They are perfectly good but not active because the oscillator is dead.
:::::: C-18 is brand new. It doesn't have any problems. One end is connected to the chassis and the other end is connected to a resistor. R3. I'll double check that it's also connected to the dead oscillator coil. It's not open. It just refuses to oscillate. All 11 paper and 2 electrolytic capacitors have been replaced. The positives of the electrolytic capacitors connect to the same place and the negatives connect to two different places.
:::::: I am getting close to removing the oscillator coil and replacing it or rewinding this one. If only I had the specs for this one. The part number on it is: 2DT200. Maybe someone has an Emerson specs book.
::::::
::::::Thanks,
::::::
::::::Dave
::::::
:::::::Dave,
:::::::The oscillator has 2 trimmers in BC mode. One on the tuning cap (C-3) and the other at the rear (C-5), either of which could hamper operation if misadjusted. The one at C-3 is common to both SW and BC. Check C-18. Also, when you tested the IF, (456kHz) were you using signal levels low to moderate or high enough to blast through at any freq?
:::::::
:::::::marv
:::::::
::::::::Marv,
:::::::: The resistors are the correct value. I checked them. I never replaced them. I also knew that the long black capacitor looking devices were also resistors. They are all correct. The capacitors are in the correct places. Nothing has been changed.
:::::::: I'll check the voltage and double check for "birdies". I think I did hear them. My huge isolation transformer is getting a lot of use on this restoration.
::::::::
::::::::Thanks,
::::::::
::::::::Dave
::::::::
:::::::::Dave,
:::::::::In reading your 2 posts, I assume the set never worked and you re-capped and replaced bad resistors first. In this case, did you replace the parts just as they were originally installed, but did you also verify their placement via the schematic?
:::::::::
:::::::::marv
:::::::::
::::::::::Radiodoc,
:::::::::: I just tried that and it makes absolutely no difference whatsoever.
:::::::::: What do I look at next?
::::::::::
::::::::::Thanks,
::::::::::
:::::::::::Dave,
:::::::::::
:::::::::::The 98 volts is probably ok. If all else failed and as a shot in the dark, I would reverse the coil leads on the non-tuned winding between B+ and the oscillator "plate" and see what happens.
:::::::::::
:::::::::::Radiodoc
:::::::::::***************
:::::::::::
::::::::::::Radiodoc,
:::::::::::: I took out the oscillator coil and checked every connection and all are good (Perfect), no opens. I checked and cleaned the band switch several times. I replaced C9 several times. When I connect 456 Kc to it from my RF signal generator, it receives that tone perfectly. It blasts!! But it wont take what's presented to it from the antenna terminals and convert that to 456 Kc. It absolutely refuses to do that under any circumstances.
:::::::::::: I checked all the connections and they are perfectly perfectly perfect. The resistors are all the correct values. The solder connections have been re-done and they are nice and shiny.
:::::::::::: I tried 3 different 6A7 tubes and none of them make any difference.
:::::::::::: I checked to make sure that the tuning capacitor or trimmer have any shorts on the oscillator side and there are no shorts. When the set is on and I try to adjust the oscillator screw or short the rotor with the stator on the oscillator side it makes no difference at all. All it's doing is "TRFing". The person who owns this radio MUST have the radio working immediately. I must continue working on it until it works. What do I do next? How do I convert it to a TRF receiver?
::::::::::::
::::::::::::Thanks,
::::::::::::
::::::::::::Dave
:::::::::::::Radiodoc,
::::::::::::: B+ is 98 volts. Is that low? Shouldn't it be a little higher? I can't see any way to raise it. Filament voltage on the 6A7 is 5.3 volts.
:::::::::::::
:::::::::::::Thanks,
:::::::::::::
:::::::::::::Dave
::::::::::::::Radiodoc,
:::::::::::::: C9 is a 100 pf capacitor. I replaced it and it made absolutely no difference.
::::::::::::::
::::::::::::::Dave
:::::::::::::::Dave,
:::::::::::::::
:::::::::::::::If all fails, walk away for a while and then come back and check carefully all the wiring around the osc circuit for correctness and good solder joints. Did you check C9 (probably a mica)or replace it. If not may try substituting another. Voltage checks on the stage may give a clue if any are off very much.
:::::::::::::::
:::::::::::::::Radiodoc
:::::::::::::::***********
:::::::::::::::
:::::::::::::::
::::::::::::::::Hello All,
:::::::::::::::: I have checked everything and the oscillator absolutely refuses to work. All paper and filter capacitors have been replaced. No part of the oscillator coil is open. The resistors are good. I tried a few 6A7s and it still wont work. What to I look at next?
:::::::::::::::: This is an AC/DC set. There's not that much there.
::::::::::::::::
::::::::::::::::Thanks,
::::::::::::::::
::::::::::::::::Dave
With the radio off did you try measuring between adjacent pins (with tube removed) to see if possibly there is an arc over between pins. You mentioned there was 2 volts on the oscillator grid. There should be a negative voltage on the oscillator grid unless you forgot to type a minus sign in front of the voltage reading you posted.
Radiodoc
************
:Marv,
: The connections and the voltages are quite good. But it still wont oscillate. It works and absolutely refuses to work all at the same time.
:
:Thanks,
:
:Dave
::Marv,
:: Yes they are. I measure the pin and the contact and I get the same reading from both. But I'll double check.
::
::Thanks,
::
::Dave
:::Dave,
:::You have eliminated almost everything. There is one remaining item though. Are you sure the socket/tube pin connections are firm?
:::
:::marv
:::
::::Edd,
:::: This oscillator is dead, dead, dead. A transistor radio will pick up nothing from it. Also, the radio works exactly the same way whether the oscillator coil is connected to the oscillator side of the tuning capacitor or not. No difference. It absolutely refuses to oscillate even though all is connected perfectly. All components are good too (except for I believe, the oscillator coil). I have more than qadruple checked the 30K, 50K, and 300 whatever ohm resistors. They are hooked up correctly. Also, the another 100pf capacitor was tried and it makes no difference. It's still dead dead dead.
:::: I don't quite understand what you want me to do with the B & K. But I was able to use the B & K to "tune" the radio in the CW position. The rest of the radio receives the 460 Kc perfectly. So it's ready for the oscillator/mixer circuit to work. I am getting ready to replace the oscillator coil. I think I can take one from another AC/DC set just to try it out. Can I do that? I see the that there is a B+ side (output) and the other side that connects to the oscillator side of the tuning capacitor. I think that the second I replace the oscillator coil it will work perfectly. Please correct me if I'm wrong.
:::: The oscillator coil has two sections on it. One is the Litz wire and the other is the enameled wire.
:::: I think that what you want me to do at the junction of c1 and R9 is to inject an oscillation to see if I can then tune the radio normally with its tuning capacitor.
::::
::::Thanks,
::::
::::Dave
:::::
:::::
:::::
:::::
:::::After reviewing your last postings info:
:::::My fustus “querstion” was if the radio operated in some degree of receiving stations ? via a tunable superheterodyne action / mode prior to the mass recapping of the unit ?
:::::
:::::
:::::
:::::Can we assume that C9..100 mmfd was ok and not even messed with ?
:::::Is cathode resistor R2 wired up ok and at its ~350 ohm value ?
:::::As well as the grid resistor of R1 ….50k wired properly and at its value ?
:::::The last item which I am sure that you did get involved with was the cathode bypass Condenser C7….05 ufd and it is OK and was reinstalled to the correct terminals…right…as that is also as critical as the 3 companion items.
:::::
:::::
:::::
:::::Looks as if the oscillator coil is on the larger ½ to ¾ in coil form and and a Litz wound unit in a tight layer…rather than the old style of enameled wire wound the full length of a long coil form. Plus, you seem to attest of its wirings continuity integrity as well as the adjunct tuning cap and its trimmer caps not being shorted out or dragging plates. Plus the additional reverting of one of the windings for a proper feed back phase check.
:::::Also with your BEE und KAY, you should be able to couple its input into the first grid of the mixer and at the proper injection of CW RF level, be able to swing its dial thru the 1005-2195 khc range and tune thru your stronger receptive stations in the area, with the two “TRF” stations being the powerhouses, BUT with the necessity of having to manually tune the tuning condenser in order to optimize the RF section being in resonance with them, when trying for weaker stations in bringing up received reception level..
:::::
:::::
:::::
:::::To further ease your mind about the radios oscillator sections L-C combinations , you could go to the juncture of C9 and R1 and couple in CW RF via a series / isolative ~100 pf cap and go to the same junction and tack on an anode of a 1N34 / 60 / 64 / 270 GERMANIUM diode and at its cathodes end , take a .001 cap for bypassing to ground and then meter the cathodes output via a VTVM.
:::::
:::::
:::::(N0…1N 914’s/4148’s/1N400oseries for this application)(Radio Shack stocks them in case you don’t have one from an oooold generation AM transistor radio chassis or from the building of a crystal set.)
:::::
:::::
:::::
:::::Then if you will power up the BEE und KAY and place in its CW mode and set the Emerson…(No power required....as this testing will be passive)…to the 1/3 lower end of the dial 700 kc ish (tuning cap ~ ¾ meshed)
:::::Then you tune the B & K in the ~1000-1400 range and see if the co-joined parasitic tuned oscillators circuit doesn’t give you a rising / declining reading as resonance was scanned across.
:::::Then, hop the radios tuning up to the higher third of the band (tuning cap ~ 1/4 meshed) and test for a like reading of a viable resonant circuit pair working at that
:::::frequency also.
:::::Thereby you have merely temp- rigged up a “po boys” grid dipper to interpret the presence of a functioning / resonating effect by the osc sections variable L-C pair and it having some degree of “Q”.
:::::
:::::
:::::The other alternative being that recurrent sweep Eico 460 Scope / Kluge of yours, so I think that with the former detected and metered RF , you would be much better off.
:::::
:::::
:::::
:::::Addenda:
:::::Noticed your new readings just at this posting time, and the bucolic local osc grid voltages reading. And have you confirmed that there is even any level oscillation by the taking of a portable xstr radios ferri-loop and placing it atop the osc coil winding and tune it off station just onto the very edge / sideband of a weaker ~1400-1740 kc AM station and then run the operating radio's tuning condenser across the bottom half of the AM band to see if even a weak heterodyning / birdie is heard on the xstr radio.
:::::
:::::Standing by for feed back
:::::
:::::
:::::73's de Edd
:::::
:::::
:::::
:::::
:::::
:::::
:::::
:::::
:::::
:::::
::::::Marv and all,
::::::
:::::: Here are the voltage readings on the 6A7 tube.
::::::
::::::Pins 1 & 7: 6.8 volts AC (Filament)
::::::Pin 2: 107.5 v DC (Plate)
::::::Pin 3: 43.5 volts DC (G3 and G5)
::::::Pin 4: 106.7 volts (G2)
::::::Pin 5: 2.2 V DC (G1)
::::::Pin 6: 2.647 volts DC (Cathode)
::::::Cap: -.361 v DC (G4)
::::::
::::::These seem like pretty healthy voltages to me. I don't see anything wrong there. The IF transformer is connecting B+ to the plate and the Oscillator coil is connecting B+ to to pin 4. So neither coil is open.
::::::
::::::I did notice that C17 was missing. I put it back and it might have made an improvement but not with the oscillator.
::::::
::::::Please if anyone has anymore ideas before I "attack" (very closely examine) the oscillator coil, please help.
::::::
::::::Thanks,
::::::
::::::Dave
::::::
:::::::Marv,
::::::: My RF signal generator modulates a 400 Hz tone on the 456 Kc carrier frequency when it's set to 456 Kc. The part of the radio that the signal generator is connected to is tune to exactly tuned to 456 Kc. It can receive 456 Kc and only 456 Kc. That "station" is received and I can blast the 400 Hz tone through the speaker of the radio. If I change the RF signal generator to another frequency, then no 400 Hz tone is heard. It is as perfectly aligned as I can get it. It may not have the best adjacent channel rejection but the signal is the strongest when the signal generator is set to 456 Kc.
::::::: The front part of the radio is what I'm having trouble with, and NOT the 456 Kc area. The radio is not converting (moving) the received frequency to 456 Kc. I can hear 570 Kc near the low end of the band and 620 Kc near the high end of the band (I live right near the brodcast antennas for these stations). That's all it does. It absolutely refuses to oscillate under any circumstances. I have checked about all I can check. All is working and not working at the same time.
::::::: The trimmers you are talking about are the oscillator trimmers that can only do anything, are only active, if the oscillator is working. I can put them in any position and they do nothing. They aren't shorted. They are perfectly good but not active because the oscillator is dead.
::::::: C-18 is brand new. It doesn't have any problems. One end is connected to the chassis and the other end is connected to a resistor. R3. I'll double check that it's also connected to the dead oscillator coil. It's not open. It just refuses to oscillate. All 11 paper and 2 electrolytic capacitors have been replaced. The positives of the electrolytic capacitors connect to the same place and the negatives connect to two different places.
::::::: I am getting close to removing the oscillator coil and replacing it or rewinding this one. If only I had the specs for this one. The part number on it is: 2DT200. Maybe someone has an Emerson specs book.
:::::::
:::::::Thanks,
:::::::
:::::::Dave
:::::::
::::::::Dave,
::::::::The oscillator has 2 trimmers in BC mode. One on the tuning cap (C-3) and the other at the rear (C-5), either of which could hamper operation if misadjusted. The one at C-3 is common to both SW and BC. Check C-18. Also, when you tested the IF, (456kHz) were you using signal levels low to moderate or high enough to blast through at any freq?
::::::::
::::::::marv
::::::::
:::::::::Marv,
::::::::: The resistors are the correct value. I checked them. I never replaced them. I also knew that the long black capacitor looking devices were also resistors. They are all correct. The capacitors are in the correct places. Nothing has been changed.
::::::::: I'll check the voltage and double check for "birdies". I think I did hear them. My huge isolation transformer is getting a lot of use on this restoration.
:::::::::
:::::::::Thanks,
:::::::::
:::::::::Dave
:::::::::
::::::::::Dave,
::::::::::In reading your 2 posts, I assume the set never worked and you re-capped and replaced bad resistors first. In this case, did you replace the parts just as they were originally installed, but did you also verify their placement via the schematic?
::::::::::
::::::::::marv
::::::::::
:::::::::::Radiodoc,
::::::::::: I just tried that and it makes absolutely no difference whatsoever.
::::::::::: What do I look at next?
:::::::::::
:::::::::::Thanks,
:::::::::::
::::::::::::Dave,
::::::::::::
::::::::::::The 98 volts is probably ok. If all else failed and as a shot in the dark, I would reverse the coil leads on the non-tuned winding between B+ and the oscillator "plate" and see what happens.
::::::::::::
::::::::::::Radiodoc
::::::::::::***************
::::::::::::
:::::::::::::Radiodoc,
::::::::::::: I took out the oscillator coil and checked every connection and all are good (Perfect), no opens. I checked and cleaned the band switch several times. I replaced C9 several times. When I connect 456 Kc to it from my RF signal generator, it receives that tone perfectly. It blasts!! But it wont take what's presented to it from the antenna terminals and convert that to 456 Kc. It absolutely refuses to do that under any circumstances.
::::::::::::: I checked all the connections and they are perfectly perfectly perfect. The resistors are all the correct values. The solder connections have been re-done and they are nice and shiny.
::::::::::::: I tried 3 different 6A7 tubes and none of them make any difference.
::::::::::::: I checked to make sure that the tuning capacitor or trimmer have any shorts on the oscillator side and there are no shorts. When the set is on and I try to adjust the oscillator screw or short the rotor with the stator on the oscillator side it makes no difference at all. All it's doing is "TRFing". The person who owns this radio MUST have the radio working immediately. I must continue working on it until it works. What do I do next? How do I convert it to a TRF receiver?
:::::::::::::
:::::::::::::Thanks,
:::::::::::::
:::::::::::::Dave
::::::::::::::Radiodoc,
:::::::::::::: B+ is 98 volts. Is that low? Shouldn't it be a little higher? I can't see any way to raise it. Filament voltage on the 6A7 is 5.3 volts.
::::::::::::::
::::::::::::::Thanks,
::::::::::::::
::::::::::::::Dave
:::::::::::::::Radiodoc,
::::::::::::::: C9 is a 100 pf capacitor. I replaced it and it made absolutely no difference.
:::::::::::::::
:::::::::::::::Dave
::::::::::::::::Dave,
::::::::::::::::
::::::::::::::::If all fails, walk away for a while and then come back and check carefully all the wiring around the osc circuit for correctness and good solder joints. Did you check C9 (probably a mica)or replace it. If not may try substituting another. Voltage checks on the stage may give a clue if any are off very much.
::::::::::::::::
::::::::::::::::Radiodoc
::::::::::::::::***********
::::::::::::::::
::::::::::::::::
:::::::::::::::::Hello All,
::::::::::::::::: I have checked everything and the oscillator absolutely refuses to work. All paper and filter capacitors have been replaced. No part of the oscillator coil is open. The resistors are good. I tried a few 6A7s and it still wont work. What to I look at next?
::::::::::::::::: This is an AC/DC set. There's not that much there.
:::::::::::::::::
:::::::::::::::::Thanks,
:::::::::::::::::
:::::::::::::::::Dave
It was 2.2 volts and it wasn't minus. What would be wrong if it's positive?
I'm going to double check that voltage.
Thanks,
Dave
:Dave,
:
:With the radio off did you try measuring between adjacent pins (with tube removed) to see if possibly there is an arc over between pins. You mentioned there was 2 volts on the oscillator grid. There should be a negative voltage on the oscillator grid unless you forgot to type a minus sign in front of the voltage reading you posted.
:
:Radiodoc
:************
:
::Marv,
:: The connections and the voltages are quite good. But it still wont oscillate. It works and absolutely refuses to work all at the same time.
::
::Thanks,
::
::Dave
:::Marv,
::: Yes they are. I measure the pin and the contact and I get the same reading from both. But I'll double check.
:::
:::Thanks,
:::
:::Dave
::::Dave,
::::You have eliminated almost everything. There is one remaining item though. Are you sure the socket/tube pin connections are firm?
::::
::::marv
::::
:::::Edd,
::::: This oscillator is dead, dead, dead. A transistor radio will pick up nothing from it. Also, the radio works exactly the same way whether the oscillator coil is connected to the oscillator side of the tuning capacitor or not. No difference. It absolutely refuses to oscillate even though all is connected perfectly. All components are good too (except for I believe, the oscillator coil). I have more than qadruple checked the 30K, 50K, and 300 whatever ohm resistors. They are hooked up correctly. Also, the another 100pf capacitor was tried and it makes no difference. It's still dead dead dead.
::::: I don't quite understand what you want me to do with the B & K. But I was able to use the B & K to "tune" the radio in the CW position. The rest of the radio receives the 460 Kc perfectly. So it's ready for the oscillator/mixer circuit to work. I am getting ready to replace the oscillator coil. I think I can take one from another AC/DC set just to try it out. Can I do that? I see the that there is a B+ side (output) and the other side that connects to the oscillator side of the tuning capacitor. I think that the second I replace the oscillator coil it will work perfectly. Please correct me if I'm wrong.
::::: The oscillator coil has two sections on it. One is the Litz wire and the other is the enameled wire.
::::: I think that what you want me to do at the junction of c1 and R9 is to inject an oscillation to see if I can then tune the radio normally with its tuning capacitor.
:::::
:::::Thanks,
:::::
:::::Dave
::::::
::::::
::::::
::::::
::::::After reviewing your last postings info:
::::::My fustus “querstion” was if the radio operated in some degree of receiving stations ? via a tunable superheterodyne action / mode prior to the mass recapping of the unit ?
::::::
::::::
::::::
::::::Can we assume that C9..100 mmfd was ok and not even messed with ?
::::::Is cathode resistor R2 wired up ok and at its ~350 ohm value ?
::::::As well as the grid resistor of R1 ….50k wired properly and at its value ?
::::::The last item which I am sure that you did get involved with was the cathode bypass Condenser C7….05 ufd and it is OK and was reinstalled to the correct terminals…right…as that is also as critical as the 3 companion items.
::::::
::::::
::::::
::::::Looks as if the oscillator coil is on the larger ½ to ¾ in coil form and and a Litz wound unit in a tight layer…rather than the old style of enameled wire wound the full length of a long coil form. Plus, you seem to attest of its wirings continuity integrity as well as the adjunct tuning cap and its trimmer caps not being shorted out or dragging plates. Plus the additional reverting of one of the windings for a proper feed back phase check.
::::::Also with your BEE und KAY, you should be able to couple its input into the first grid of the mixer and at the proper injection of CW RF level, be able to swing its dial thru the 1005-2195 khc range and tune thru your stronger receptive stations in the area, with the two “TRF” stations being the powerhouses, BUT with the necessity of having to manually tune the tuning condenser in order to optimize the RF section being in resonance with them, when trying for weaker stations in bringing up received reception level..
::::::
::::::
::::::
::::::To further ease your mind about the radios oscillator sections L-C combinations , you could go to the juncture of C9 and R1 and couple in CW RF via a series / isolative ~100 pf cap and go to the same junction and tack on an anode of a 1N34 / 60 / 64 / 270 GERMANIUM diode and at its cathodes end , take a .001 cap for bypassing to ground and then meter the cathodes output via a VTVM.
::::::
::::::
::::::(N0…1N 914’s/4148’s/1N400oseries for this application)(Radio Shack stocks them in case you don’t have one from an oooold generation AM transistor radio chassis or from the building of a crystal set.)
::::::
::::::
::::::
::::::Then if you will power up the BEE und KAY and place in its CW mode and set the Emerson…(No power required....as this testing will be passive)…to the 1/3 lower end of the dial 700 kc ish (tuning cap ~ ¾ meshed)
::::::Then you tune the B & K in the ~1000-1400 range and see if the co-joined parasitic tuned oscillators circuit doesn’t give you a rising / declining reading as resonance was scanned across.
::::::Then, hop the radios tuning up to the higher third of the band (tuning cap ~ 1/4 meshed) and test for a like reading of a viable resonant circuit pair working at that
::::::frequency also.
::::::Thereby you have merely temp- rigged up a “po boys” grid dipper to interpret the presence of a functioning / resonating effect by the osc sections variable L-C pair and it having some degree of “Q”.
::::::
::::::
::::::The other alternative being that recurrent sweep Eico 460 Scope / Kluge of yours, so I think that with the former detected and metered RF , you would be much better off.
::::::
::::::
::::::
::::::Addenda:
::::::Noticed your new readings just at this posting time, and the bucolic local osc grid voltages reading. And have you confirmed that there is even any level oscillation by the taking of a portable xstr radios ferri-loop and placing it atop the osc coil winding and tune it off station just onto the very edge / sideband of a weaker ~1400-1740 kc AM station and then run the operating radio's tuning condenser across the bottom half of the AM band to see if even a weak heterodyning / birdie is heard on the xstr radio.
::::::
::::::Standing by for feed back
::::::
::::::
::::::73's de Edd
::::::
::::::
::::::
::::::
::::::
::::::
::::::
::::::
::::::
::::::
:::::::Marv and all,
:::::::
::::::: Here are the voltage readings on the 6A7 tube.
:::::::
:::::::Pins 1 & 7: 6.8 volts AC (Filament)
:::::::Pin 2: 107.5 v DC (Plate)
:::::::Pin 3: 43.5 volts DC (G3 and G5)
:::::::Pin 4: 106.7 volts (G2)
:::::::Pin 5: 2.2 V DC (G1)
:::::::Pin 6: 2.647 volts DC (Cathode)
:::::::Cap: -.361 v DC (G4)
:::::::
:::::::These seem like pretty healthy voltages to me. I don't see anything wrong there. The IF transformer is connecting B+ to the plate and the Oscillator coil is connecting B+ to to pin 4. So neither coil is open.
:::::::
:::::::I did notice that C17 was missing. I put it back and it might have made an improvement but not with the oscillator.
:::::::
:::::::Please if anyone has anymore ideas before I "attack" (very closely examine) the oscillator coil, please help.
:::::::
:::::::Thanks,
:::::::
:::::::Dave
:::::::
::::::::Marv,
:::::::: My RF signal generator modulates a 400 Hz tone on the 456 Kc carrier frequency when it's set to 456 Kc. The part of the radio that the signal generator is connected to is tune to exactly tuned to 456 Kc. It can receive 456 Kc and only 456 Kc. That "station" is received and I can blast the 400 Hz tone through the speaker of the radio. If I change the RF signal generator to another frequency, then no 400 Hz tone is heard. It is as perfectly aligned as I can get it. It may not have the best adjacent channel rejection but the signal is the strongest when the signal generator is set to 456 Kc.
:::::::: The front part of the radio is what I'm having trouble with, and NOT the 456 Kc area. The radio is not converting (moving) the received frequency to 456 Kc. I can hear 570 Kc near the low end of the band and 620 Kc near the high end of the band (I live right near the brodcast antennas for these stations). That's all it does. It absolutely refuses to oscillate under any circumstances. I have checked about all I can check. All is working and not working at the same time.
:::::::: The trimmers you are talking about are the oscillator trimmers that can only do anything, are only active, if the oscillator is working. I can put them in any position and they do nothing. They aren't shorted. They are perfectly good but not active because the oscillator is dead.
:::::::: C-18 is brand new. It doesn't have any problems. One end is connected to the chassis and the other end is connected to a resistor. R3. I'll double check that it's also connected to the dead oscillator coil. It's not open. It just refuses to oscillate. All 11 paper and 2 electrolytic capacitors have been replaced. The positives of the electrolytic capacitors connect to the same place and the negatives connect to two different places.
:::::::: I am getting close to removing the oscillator coil and replacing it or rewinding this one. If only I had the specs for this one. The part number on it is: 2DT200. Maybe someone has an Emerson specs book.
::::::::
::::::::Thanks,
::::::::
::::::::Dave
::::::::
:::::::::Dave,
:::::::::The oscillator has 2 trimmers in BC mode. One on the tuning cap (C-3) and the other at the rear (C-5), either of which could hamper operation if misadjusted. The one at C-3 is common to both SW and BC. Check C-18. Also, when you tested the IF, (456kHz) were you using signal levels low to moderate or high enough to blast through at any freq?
:::::::::
:::::::::marv
:::::::::
::::::::::Marv,
:::::::::: The resistors are the correct value. I checked them. I never replaced them. I also knew that the long black capacitor looking devices were also resistors. They are all correct. The capacitors are in the correct places. Nothing has been changed.
:::::::::: I'll check the voltage and double check for "birdies". I think I did hear them. My huge isolation transformer is getting a lot of use on this restoration.
::::::::::
::::::::::Thanks,
::::::::::
::::::::::Dave
::::::::::
:::::::::::Dave,
:::::::::::In reading your 2 posts, I assume the set never worked and you re-capped and replaced bad resistors first. In this case, did you replace the parts just as they were originally installed, but did you also verify their placement via the schematic?
:::::::::::
:::::::::::marv
:::::::::::
::::::::::::Radiodoc,
:::::::::::: I just tried that and it makes absolutely no difference whatsoever.
:::::::::::: What do I look at next?
::::::::::::
::::::::::::Thanks,
::::::::::::
:::::::::::::Dave,
:::::::::::::
:::::::::::::The 98 volts is probably ok. If all else failed and as a shot in the dark, I would reverse the coil leads on the non-tuned winding between B+ and the oscillator "plate" and see what happens.
:::::::::::::
:::::::::::::Radiodoc
:::::::::::::***************
:::::::::::::
::::::::::::::Radiodoc,
:::::::::::::: I took out the oscillator coil and checked every connection and all are good (Perfect), no opens. I checked and cleaned the band switch several times. I replaced C9 several times. When I connect 456 Kc to it from my RF signal generator, it receives that tone perfectly. It blasts!! But it wont take what's presented to it from the antenna terminals and convert that to 456 Kc. It absolutely refuses to do that under any circumstances.
:::::::::::::: I checked all the connections and they are perfectly perfectly perfect. The resistors are all the correct values. The solder connections have been re-done and they are nice and shiny.
:::::::::::::: I tried 3 different 6A7 tubes and none of them make any difference.
:::::::::::::: I checked to make sure that the tuning capacitor or trimmer have any shorts on the oscillator side and there are no shorts. When the set is on and I try to adjust the oscillator screw or short the rotor with the stator on the oscillator side it makes no difference at all. All it's doing is "TRFing". The person who owns this radio MUST have the radio working immediately. I must continue working on it until it works. What do I do next? How do I convert it to a TRF receiver?
::::::::::::::
::::::::::::::Thanks,
::::::::::::::
::::::::::::::Dave
:::::::::::::::Radiodoc,
::::::::::::::: B+ is 98 volts. Is that low? Shouldn't it be a little higher? I can't see any way to raise it. Filament voltage on the 6A7 is 5.3 volts.
:::::::::::::::
:::::::::::::::Thanks,
:::::::::::::::
:::::::::::::::Dave
::::::::::::::::Radiodoc,
:::::::::::::::: C9 is a 100 pf capacitor. I replaced it and it made absolutely no difference.
::::::::::::::::
::::::::::::::::Dave
:::::::::::::::::Dave,
:::::::::::::::::
:::::::::::::::::If all fails, walk away for a while and then come back and check carefully all the wiring around the osc circuit for correctness and good solder joints. Did you check C9 (probably a mica)or replace it. If not may try substituting another. Voltage checks on the stage may give a clue if any are off very much.
:::::::::::::::::
:::::::::::::::::Radiodoc
:::::::::::::::::***********
:::::::::::::::::
:::::::::::::::::
::::::::::::::::::Hello All,
:::::::::::::::::: I have checked everything and the oscillator absolutely refuses to work. All paper and filter capacitors have been replaced. No part of the oscillator coil is open. The resistors are good. I tried a few 6A7s and it still wont work. What to I look at next?
:::::::::::::::::: This is an AC/DC set. There's not that much there.
::::::::::::::::::
::::::::::::::::::Thanks,
::::::::::::::::::
::::::::::::::::::Dave
Radiodoc,
Yes, it is positive. Pin 5 is 2.4 volts and pin 6 is 2.8 volts now. The only pins that are negative are the filament pins which are -23 volts DC with respect to the chassis. But they are 6.8 volts AC when I measure across the filament.
Is there something else wrong elsewhere in the set that's preventing the oscillator from working?
Thanks,
Dave
:Radiodoc,
: It was 2.2 volts and it wasn't minus. What would be wrong if it's positive?
: I'm going to double check that voltage.
:
:Thanks,
:
:Dave
::Dave,
::
::With the radio off did you try measuring between adjacent pins (with tube removed) to see if possibly there is an arc over between pins. You mentioned there was 2 volts on the oscillator grid. There should be a negative voltage on the oscillator grid unless you forgot to type a minus sign in front of the voltage reading you posted.
::
::Radiodoc
::************
::
:::Marv,
::: The connections and the voltages are quite good. But it still wont oscillate. It works and absolutely refuses to work all at the same time.
:::
:::Thanks,
:::
:::Dave
::::Marv,
:::: Yes they are. I measure the pin and the contact and I get the same reading from both. But I'll double check.
::::
::::Thanks,
::::
::::Dave
:::::Dave,
:::::You have eliminated almost everything. There is one remaining item though. Are you sure the socket/tube pin connections are firm?
:::::
:::::marv
:::::
::::::Edd,
:::::: This oscillator is dead, dead, dead. A transistor radio will pick up nothing from it. Also, the radio works exactly the same way whether the oscillator coil is connected to the oscillator side of the tuning capacitor or not. No difference. It absolutely refuses to oscillate even though all is connected perfectly. All components are good too (except for I believe, the oscillator coil). I have more than qadruple checked the 30K, 50K, and 300 whatever ohm resistors. They are hooked up correctly. Also, the another 100pf capacitor was tried and it makes no difference. It's still dead dead dead.
:::::: I don't quite understand what you want me to do with the B & K. But I was able to use the B & K to "tune" the radio in the CW position. The rest of the radio receives the 460 Kc perfectly. So it's ready for the oscillator/mixer circuit to work. I am getting ready to replace the oscillator coil. I think I can take one from another AC/DC set just to try it out. Can I do that? I see the that there is a B+ side (output) and the other side that connects to the oscillator side of the tuning capacitor. I think that the second I replace the oscillator coil it will work perfectly. Please correct me if I'm wrong.
:::::: The oscillator coil has two sections on it. One is the Litz wire and the other is the enameled wire.
:::::: I think that what you want me to do at the junction of c1 and R9 is to inject an oscillation to see if I can then tune the radio normally with its tuning capacitor.
::::::
::::::Thanks,
::::::
::::::Dave
:::::::
:::::::
:::::::
:::::::
:::::::After reviewing your last postings info:
:::::::My fustus “querstion” was if the radio operated in some degree of receiving stations ? via a tunable superheterodyne action / mode prior to the mass recapping of the unit ?
:::::::
:::::::
:::::::
:::::::Can we assume that C9..100 mmfd was ok and not even messed with ?
:::::::Is cathode resistor R2 wired up ok and at its ~350 ohm value ?
:::::::As well as the grid resistor of R1 ….50k wired properly and at its value ?
:::::::The last item which I am sure that you did get involved with was the cathode bypass Condenser C7….05 ufd and it is OK and was reinstalled to the correct terminals…right…as that is also as critical as the 3 companion items.
:::::::
:::::::
:::::::
:::::::Looks as if the oscillator coil is on the larger ½ to ¾ in coil form and and a Litz wound unit in a tight layer…rather than the old style of enameled wire wound the full length of a long coil form. Plus, you seem to attest of its wirings continuity integrity as well as the adjunct tuning cap and its trimmer caps not being shorted out or dragging plates. Plus the additional reverting of one of the windings for a proper feed back phase check.
:::::::Also with your BEE und KAY, you should be able to couple its input into the first grid of the mixer and at the proper injection of CW RF level, be able to swing its dial thru the 1005-2195 khc range and tune thru your stronger receptive stations in the area, with the two “TRF” stations being the powerhouses, BUT with the necessity of having to manually tune the tuning condenser in order to optimize the RF section being in resonance with them, when trying for weaker stations in bringing up received reception level..
:::::::
:::::::
:::::::
:::::::To further ease your mind about the radios oscillator sections L-C combinations , you could go to the juncture of C9 and R1 and couple in CW RF via a series / isolative ~100 pf cap and go to the same junction and tack on an anode of a 1N34 / 60 / 64 / 270 GERMANIUM diode and at its cathodes end , take a .001 cap for bypassing to ground and then meter the cathodes output via a VTVM.
:::::::
:::::::
:::::::(N0…1N 914’s/4148’s/1N400oseries for this application)(Radio Shack stocks them in case you don’t have one from an oooold generation AM transistor radio chassis or from the building of a crystal set.)
:::::::
:::::::
:::::::
:::::::Then if you will power up the BEE und KAY and place in its CW mode and set the Emerson…(No power required....as this testing will be passive)…to the 1/3 lower end of the dial 700 kc ish (tuning cap ~ ¾ meshed)
:::::::Then you tune the B & K in the ~1000-1400 range and see if the co-joined parasitic tuned oscillators circuit doesn’t give you a rising / declining reading as resonance was scanned across.
:::::::Then, hop the radios tuning up to the higher third of the band (tuning cap ~ 1/4 meshed) and test for a like reading of a viable resonant circuit pair working at that
:::::::frequency also.
:::::::Thereby you have merely temp- rigged up a “po boys” grid dipper to interpret the presence of a functioning / resonating effect by the osc sections variable L-C pair and it having some degree of “Q”.
:::::::
:::::::
:::::::The other alternative being that recurrent sweep Eico 460 Scope / Kluge of yours, so I think that with the former detected and metered RF , you would be much better off.
:::::::
:::::::
:::::::
:::::::Addenda:
:::::::Noticed your new readings just at this posting time, and the bucolic local osc grid voltages reading. And have you confirmed that there is even any level oscillation by the taking of a portable xstr radios ferri-loop and placing it atop the osc coil winding and tune it off station just onto the very edge / sideband of a weaker ~1400-1740 kc AM station and then run the operating radio's tuning condenser across the bottom half of the AM band to see if even a weak heterodyning / birdie is heard on the xstr radio.
:::::::
:::::::Standing by for feed back
:::::::
:::::::
:::::::73's de Edd
:::::::
:::::::
:::::::
:::::::
:::::::
:::::::
:::::::
:::::::
:::::::
:::::::
::::::::Marv and all,
::::::::
:::::::: Here are the voltage readings on the 6A7 tube.
::::::::
::::::::Pins 1 & 7: 6.8 volts AC (Filament)
::::::::Pin 2: 107.5 v DC (Plate)
::::::::Pin 3: 43.5 volts DC (G3 and G5)
::::::::Pin 4: 106.7 volts (G2)
::::::::Pin 5: 2.2 V DC (G1)
::::::::Pin 6: 2.647 volts DC (Cathode)
::::::::Cap: -.361 v DC (G4)
::::::::
::::::::These seem like pretty healthy voltages to me. I don't see anything wrong there. The IF transformer is connecting B+ to the plate and the Oscillator coil is connecting B+ to to pin 4. So neither coil is open.
::::::::
::::::::I did notice that C17 was missing. I put it back and it might have made an improvement but not with the oscillator.
::::::::
::::::::Please if anyone has anymore ideas before I "attack" (very closely examine) the oscillator coil, please help.
::::::::
::::::::Thanks,
::::::::
::::::::Dave
::::::::
:::::::::Marv,
::::::::: My RF signal generator modulates a 400 Hz tone on the 456 Kc carrier frequency when it's set to 456 Kc. The part of the radio that the signal generator is connected to is tune to exactly tuned to 456 Kc. It can receive 456 Kc and only 456 Kc. That "station" is received and I can blast the 400 Hz tone through the speaker of the radio. If I change the RF signal generator to another frequency, then no 400 Hz tone is heard. It is as perfectly aligned as I can get it. It may not have the best adjacent channel rejection but the signal is the strongest when the signal generator is set to 456 Kc.
::::::::: The front part of the radio is what I'm having trouble with, and NOT the 456 Kc area. The radio is not converting (moving) the received frequency to 456 Kc. I can hear 570 Kc near the low end of the band and 620 Kc near the high end of the band (I live right near the brodcast antennas for these stations). That's all it does. It absolutely refuses to oscillate under any circumstances. I have checked about all I can check. All is working and not working at the same time.
::::::::: The trimmers you are talking about are the oscillator trimmers that can only do anything, are only active, if the oscillator is working. I can put them in any position and they do nothing. They aren't shorted. They are perfectly good but not active because the oscillator is dead.
::::::::: C-18 is brand new. It doesn't have any problems. One end is connected to the chassis and the other end is connected to a resistor. R3. I'll double check that it's also connected to the dead oscillator coil. It's not open. It just refuses to oscillate. All 11 paper and 2 electrolytic capacitors have been replaced. The positives of the electrolytic capacitors connect to the same place and the negatives connect to two different places.
::::::::: I am getting close to removing the oscillator coil and replacing it or rewinding this one. If only I had the specs for this one. The part number on it is: 2DT200. Maybe someone has an Emerson specs book.
:::::::::
:::::::::Thanks,
:::::::::
:::::::::Dave
:::::::::
::::::::::Dave,
::::::::::The oscillator has 2 trimmers in BC mode. One on the tuning cap (C-3) and the other at the rear (C-5), either of which could hamper operation if misadjusted. The one at C-3 is common to both SW and BC. Check C-18. Also, when you tested the IF, (456kHz) were you using signal levels low to moderate or high enough to blast through at any freq?
::::::::::
::::::::::marv
::::::::::
:::::::::::Marv,
::::::::::: The resistors are the correct value. I checked them. I never replaced them. I also knew that the long black capacitor looking devices were also resistors. They are all correct. The capacitors are in the correct places. Nothing has been changed.
::::::::::: I'll check the voltage and double check for "birdies". I think I did hear them. My huge isolation transformer is getting a lot of use on this restoration.
:::::::::::
:::::::::::Thanks,
:::::::::::
:::::::::::Dave
:::::::::::
::::::::::::Dave,
::::::::::::In reading your 2 posts, I assume the set never worked and you re-capped and replaced bad resistors first. In this case, did you replace the parts just as they were originally installed, but did you also verify their placement via the schematic?
::::::::::::
::::::::::::marv
::::::::::::
:::::::::::::Radiodoc,
::::::::::::: I just tried that and it makes absolutely no difference whatsoever.
::::::::::::: What do I look at next?
:::::::::::::
:::::::::::::Thanks,
:::::::::::::
::::::::::::::Dave,
::::::::::::::
::::::::::::::The 98 volts is probably ok. If all else failed and as a shot in the dark, I would reverse the coil leads on the non-tuned winding between B+ and the oscillator "plate" and see what happens.
::::::::::::::
::::::::::::::Radiodoc
::::::::::::::***************
::::::::::::::
:::::::::::::::Radiodoc,
::::::::::::::: I took out the oscillator coil and checked every connection and all are good (Perfect), no opens. I checked and cleaned the band switch several times. I replaced C9 several times. When I connect 456 Kc to it from my RF signal generator, it receives that tone perfectly. It blasts!! But it wont take what's presented to it from the antenna terminals and convert that to 456 Kc. It absolutely refuses to do that under any circumstances.
::::::::::::::: I checked all the connections and they are perfectly perfectly perfect. The resistors are all the correct values. The solder connections have been re-done and they are nice and shiny.
::::::::::::::: I tried 3 different 6A7 tubes and none of them make any difference.
::::::::::::::: I checked to make sure that the tuning capacitor or trimmer have any shorts on the oscillator side and there are no shorts. When the set is on and I try to adjust the oscillator screw or short the rotor with the stator on the oscillator side it makes no difference at all. All it's doing is "TRFing". The person who owns this radio MUST have the radio working immediately. I must continue working on it until it works. What do I do next? How do I convert it to a TRF receiver?
:::::::::::::::
:::::::::::::::Thanks,
:::::::::::::::
:::::::::::::::Dave
::::::::::::::::Radiodoc,
:::::::::::::::: B+ is 98 volts. Is that low? Shouldn't it be a little higher? I can't see any way to raise it. Filament voltage on the 6A7 is 5.3 volts.
::::::::::::::::
::::::::::::::::Thanks,
::::::::::::::::
::::::::::::::::Dave
:::::::::::::::::Radiodoc,
::::::::::::::::: C9 is a 100 pf capacitor. I replaced it and it made absolutely no difference.
:::::::::::::::::
:::::::::::::::::Dave
::::::::::::::::::Dave,
::::::::::::::::::
::::::::::::::::::If all fails, walk away for a while and then come back and check carefully all the wiring around the osc circuit for correctness and good solder joints. Did you check C9 (probably a mica)or replace it. If not may try substituting another. Voltage checks on the stage may give a clue if any are off very much.
::::::::::::::::::
::::::::::::::::::Radiodoc
::::::::::::::::::***********
::::::::::::::::::
::::::::::::::::::
:::::::::::::::::::Hello All,
::::::::::::::::::: I have checked everything and the oscillator absolutely refuses to work. All paper and filter capacitors have been replaced. No part of the oscillator coil is open. The resistors are good. I tried a few 6A7s and it still wont work. What to I look at next?
::::::::::::::::::: This is an AC/DC set. There's not that much there.
:::::::::::::::::::
:::::::::::::::::::Thanks,
:::::::::::::::::::
:::::::::::::::::::Dave
I just looked through the archives and found that if the voltage is positive it means that the oscillator is not operating. This is what I have been trying to tell you. The oscillator is dead. Ok, good, now we have absolute proof that the oscillator is dead. Now what do I look for? There could still be something not working. The oscillator coil? There is continuity but I don't know what it's value is in micro-henries. All I know is that it's a transformer. It has two primaries for the two bands, and one secondary. The part number on the oscillator coil 2DT200 matches the number in the service data. So it is original.
I'll keep checking the archives to see what others have done in this situation. I think that this may be a common problem. If you know what to check please let me know.
Thanks,
Dave
:
:Radiodoc,
: Yes, it is positive. Pin 5 is 2.4 volts and pin 6 is 2.8 volts now. The only pins that are negative are the filament pins which are -23 volts DC with respect to the chassis. But they are 6.8 volts AC when I measure across the filament.
: Is there something else wrong elsewhere in the set that's preventing the oscillator from working?
:
:Thanks,
:
:Dave
:
::Radiodoc,
:: It was 2.2 volts and it wasn't minus. What would be wrong if it's positive?
:: I'm going to double check that voltage.
::
::Thanks,
::
::Dave
:::Dave,
:::
:::With the radio off did you try measuring between adjacent pins (with tube removed) to see if possibly there is an arc over between pins. You mentioned there was 2 volts on the oscillator grid. There should be a negative voltage on the oscillator grid unless you forgot to type a minus sign in front of the voltage reading you posted.
:::
:::Radiodoc
:::************
:::
::::Marv,
:::: The connections and the voltages are quite good. But it still wont oscillate. It works and absolutely refuses to work all at the same time.
::::
::::Thanks,
::::
::::Dave
:::::Marv,
::::: Yes they are. I measure the pin and the contact and I get the same reading from both. But I'll double check.
:::::
:::::Thanks,
:::::
:::::Dave
::::::Dave,
::::::You have eliminated almost everything. There is one remaining item though. Are you sure the socket/tube pin connections are firm?
::::::
::::::marv
::::::
:::::::Edd,
::::::: This oscillator is dead, dead, dead. A transistor radio will pick up nothing from it. Also, the radio works exactly the same way whether the oscillator coil is connected to the oscillator side of the tuning capacitor or not. No difference. It absolutely refuses to oscillate even though all is connected perfectly. All components are good too (except for I believe, the oscillator coil). I have more than qadruple checked the 30K, 50K, and 300 whatever ohm resistors. They are hooked up correctly. Also, the another 100pf capacitor was tried and it makes no difference. It's still dead dead dead.
::::::: I don't quite understand what you want me to do with the B & K. But I was able to use the B & K to "tune" the radio in the CW position. The rest of the radio receives the 460 Kc perfectly. So it's ready for the oscillator/mixer circuit to work. I am getting ready to replace the oscillator coil. I think I can take one from another AC/DC set just to try it out. Can I do that? I see the that there is a B+ side (output) and the other side that connects to the oscillator side of the tuning capacitor. I think that the second I replace the oscillator coil it will work perfectly. Please correct me if I'm wrong.
::::::: The oscillator coil has two sections on it. One is the Litz wire and the other is the enameled wire.
::::::: I think that what you want me to do at the junction of c1 and R9 is to inject an oscillation to see if I can then tune the radio normally with its tuning capacitor.
:::::::
:::::::Thanks,
:::::::
:::::::Dave
::::::::
::::::::
::::::::
::::::::
::::::::After reviewing your last postings info:
::::::::My fustus “querstion” was if the radio operated in some degree of receiving stations ? via a tunable superheterodyne action / mode prior to the mass recapping of the unit ?
::::::::
::::::::
::::::::
::::::::Can we assume that C9..100 mmfd was ok and not even messed with ?
::::::::Is cathode resistor R2 wired up ok and at its ~350 ohm value ?
::::::::As well as the grid resistor of R1 ….50k wired properly and at its value ?
::::::::The last item which I am sure that you did get involved with was the cathode bypass Condenser C7….05 ufd and it is OK and was reinstalled to the correct terminals…right…as that is also as critical as the 3 companion items.
::::::::
::::::::
::::::::
::::::::Looks as if the oscillator coil is on the larger ½ to ¾ in coil form and and a Litz wound unit in a tight layer…rather than the old style of enameled wire wound the full length of a long coil form. Plus, you seem to attest of its wirings continuity integrity as well as the adjunct tuning cap and its trimmer caps not being shorted out or dragging plates. Plus the additional reverting of one of the windings for a proper feed back phase check.
::::::::Also with your BEE und KAY, you should be able to couple its input into the first grid of the mixer and at the proper injection of CW RF level, be able to swing its dial thru the 1005-2195 khc range and tune thru your stronger receptive stations in the area, with the two “TRF” stations being the powerhouses, BUT with the necessity of having to manually tune the tuning condenser in order to optimize the RF section being in resonance with them, when trying for weaker stations in bringing up received reception level..
::::::::
::::::::
::::::::
::::::::To further ease your mind about the radios oscillator sections L-C combinations , you could go to the juncture of C9 and R1 and couple in CW RF via a series / isolative ~100 pf cap and go to the same junction and tack on an anode of a 1N34 / 60 / 64 / 270 GERMANIUM diode and at its cathodes end , take a .001 cap for bypassing to ground and then meter the cathodes output via a VTVM.
::::::::
::::::::
::::::::(N0…1N 914’s/4148’s/1N400oseries for this application)(Radio Shack stocks them in case you don’t have one from an oooold generation AM transistor radio chassis or from the building of a crystal set.)
::::::::
::::::::
::::::::
::::::::Then if you will power up the BEE und KAY and place in its CW mode and set the Emerson…(No power required....as this testing will be passive)…to the 1/3 lower end of the dial 700 kc ish (tuning cap ~ ¾ meshed)
::::::::Then you tune the B & K in the ~1000-1400 range and see if the co-joined parasitic tuned oscillators circuit doesn’t give you a rising / declining reading as resonance was scanned across.
::::::::Then, hop the radios tuning up to the higher third of the band (tuning cap ~ 1/4 meshed) and test for a like reading of a viable resonant circuit pair working at that
::::::::frequency also.
::::::::Thereby you have merely temp- rigged up a “po boys” grid dipper to interpret the presence of a functioning / resonating effect by the osc sections variable L-C pair and it having some degree of “Q”.
::::::::
::::::::
::::::::The other alternative being that recurrent sweep Eico 460 Scope / Kluge of yours, so I think that with the former detected and metered RF , you would be much better off.
::::::::
::::::::
::::::::
::::::::Addenda:
::::::::Noticed your new readings just at this posting time, and the bucolic local osc grid voltages reading. And have you confirmed that there is even any level oscillation by the taking of a portable xstr radios ferri-loop and placing it atop the osc coil winding and tune it off station just onto the very edge / sideband of a weaker ~1400-1740 kc AM station and then run the operating radio's tuning condenser across the bottom half of the AM band to see if even a weak heterodyning / birdie is heard on the xstr radio.
::::::::
::::::::Standing by for feed back
::::::::
::::::::
::::::::73's de Edd
::::::::
::::::::
::::::::
::::::::
::::::::
::::::::
::::::::
::::::::
::::::::
::::::::
:::::::::Marv and all,
:::::::::
::::::::: Here are the voltage readings on the 6A7 tube.
:::::::::
:::::::::Pins 1 & 7: 6.8 volts AC (Filament)
:::::::::Pin 2: 107.5 v DC (Plate)
:::::::::Pin 3: 43.5 volts DC (G3 and G5)
:::::::::Pin 4: 106.7 volts (G2)
:::::::::Pin 5: 2.2 V DC (G1)
:::::::::Pin 6: 2.647 volts DC (Cathode)
:::::::::Cap: -.361 v DC (G4)
:::::::::
:::::::::These seem like pretty healthy voltages to me. I don't see anything wrong there. The IF transformer is connecting B+ to the plate and the Oscillator coil is connecting B+ to to pin 4. So neither coil is open.
:::::::::
:::::::::I did notice that C17 was missing. I put it back and it might have made an improvement but not with the oscillator.
:::::::::
:::::::::Please if anyone has anymore ideas before I "attack" (very closely examine) the oscillator coil, please help.
:::::::::
:::::::::Thanks,
:::::::::
:::::::::Dave
:::::::::
::::::::::Marv,
:::::::::: My RF signal generator modulates a 400 Hz tone on the 456 Kc carrier frequency when it's set to 456 Kc. The part of the radio that the signal generator is connected to is tune to exactly tuned to 456 Kc. It can receive 456 Kc and only 456 Kc. That "station" is received and I can blast the 400 Hz tone through the speaker of the radio. If I change the RF signal generator to another frequency, then no 400 Hz tone is heard. It is as perfectly aligned as I can get it. It may not have the best adjacent channel rejection but the signal is the strongest when the signal generator is set to 456 Kc.
:::::::::: The front part of the radio is what I'm having trouble with, and NOT the 456 Kc area. The radio is not converting (moving) the received frequency to 456 Kc. I can hear 570 Kc near the low end of the band and 620 Kc near the high end of the band (I live right near the brodcast antennas for these stations). That's all it does. It absolutely refuses to oscillate under any circumstances. I have checked about all I can check. All is working and not working at the same time.
:::::::::: The trimmers you are talking about are the oscillator trimmers that can only do anything, are only active, if the oscillator is working. I can put them in any position and they do nothing. They aren't shorted. They are perfectly good but not active because the oscillator is dead.
:::::::::: C-18 is brand new. It doesn't have any problems. One end is connected to the chassis and the other end is connected to a resistor. R3. I'll double check that it's also connected to the dead oscillator coil. It's not open. It just refuses to oscillate. All 11 paper and 2 electrolytic capacitors have been replaced. The positives of the electrolytic capacitors connect to the same place and the negatives connect to two different places.
:::::::::: I am getting close to removing the oscillator coil and replacing it or rewinding this one. If only I had the specs for this one. The part number on it is: 2DT200. Maybe someone has an Emerson specs book.
::::::::::
::::::::::Thanks,
::::::::::
::::::::::Dave
::::::::::
:::::::::::Dave,
:::::::::::The oscillator has 2 trimmers in BC mode. One on the tuning cap (C-3) and the other at the rear (C-5), either of which could hamper operation if misadjusted. The one at C-3 is common to both SW and BC. Check C-18. Also, when you tested the IF, (456kHz) were you using signal levels low to moderate or high enough to blast through at any freq?
:::::::::::
:::::::::::marv
:::::::::::
::::::::::::Marv,
:::::::::::: The resistors are the correct value. I checked them. I never replaced them. I also knew that the long black capacitor looking devices were also resistors. They are all correct. The capacitors are in the correct places. Nothing has been changed.
:::::::::::: I'll check the voltage and double check for "birdies". I think I did hear them. My huge isolation transformer is getting a lot of use on this restoration.
::::::::::::
::::::::::::Thanks,
::::::::::::
::::::::::::Dave
::::::::::::
:::::::::::::Dave,
:::::::::::::In reading your 2 posts, I assume the set never worked and you re-capped and replaced bad resistors first. In this case, did you replace the parts just as they were originally installed, but did you also verify their placement via the schematic?
:::::::::::::
:::::::::::::marv
:::::::::::::
::::::::::::::Radiodoc,
:::::::::::::: I just tried that and it makes absolutely no difference whatsoever.
:::::::::::::: What do I look at next?
::::::::::::::
::::::::::::::Thanks,
::::::::::::::
:::::::::::::::Dave,
:::::::::::::::
:::::::::::::::The 98 volts is probably ok. If all else failed and as a shot in the dark, I would reverse the coil leads on the non-tuned winding between B+ and the oscillator "plate" and see what happens.
:::::::::::::::
:::::::::::::::Radiodoc
:::::::::::::::***************
:::::::::::::::
::::::::::::::::Radiodoc,
:::::::::::::::: I took out the oscillator coil and checked every connection and all are good (Perfect), no opens. I checked and cleaned the band switch several times. I replaced C9 several times. When I connect 456 Kc to it from my RF signal generator, it receives that tone perfectly. It blasts!! But it wont take what's presented to it from the antenna terminals and convert that to 456 Kc. It absolutely refuses to do that under any circumstances.
:::::::::::::::: I checked all the connections and they are perfectly perfectly perfect. The resistors are all the correct values. The solder connections have been re-done and they are nice and shiny.
:::::::::::::::: I tried 3 different 6A7 tubes and none of them make any difference.
:::::::::::::::: I checked to make sure that the tuning capacitor or trimmer have any shorts on the oscillator side and there are no shorts. When the set is on and I try to adjust the oscillator screw or short the rotor with the stator on the oscillator side it makes no difference at all. All it's doing is "TRFing". The person who owns this radio MUST have the radio working immediately. I must continue working on it until it works. What do I do next? How do I convert it to a TRF receiver?
::::::::::::::::
::::::::::::::::Thanks,
::::::::::::::::
::::::::::::::::Dave
:::::::::::::::::Radiodoc,
::::::::::::::::: B+ is 98 volts. Is that low? Shouldn't it be a little higher? I can't see any way to raise it. Filament voltage on the 6A7 is 5.3 volts.
:::::::::::::::::
:::::::::::::::::Thanks,
:::::::::::::::::
:::::::::::::::::Dave
::::::::::::::::::Radiodoc,
:::::::::::::::::: C9 is a 100 pf capacitor. I replaced it and it made absolutely no difference.
::::::::::::::::::
::::::::::::::::::Dave
:::::::::::::::::::Dave,
:::::::::::::::::::
:::::::::::::::::::If all fails, walk away for a while and then come back and check carefully all the wiring around the osc circuit for correctness and good solder joints. Did you check C9 (probably a mica)or replace it. If not may try substituting another. Voltage checks on the stage may give a clue if any are off very much.
:::::::::::::::::::
:::::::::::::::::::Radiodoc
:::::::::::::::::::***********
:::::::::::::::::::
:::::::::::::::::::
::::::::::::::::::::Hello All,
:::::::::::::::::::: I have checked everything and the oscillator absolutely refuses to work. All paper and filter capacitors have been replaced. No part of the oscillator coil is open. The resistors are good. I tried a few 6A7s and it still wont work. What to I look at next?
:::::::::::::::::::: This is an AC/DC set. There's not that much there.
::::::::::::::::::::
::::::::::::::::::::Thanks,
::::::::::::::::::::
::::::::::::::::::::Dave
Bill VA
:Radiodoc,
: I just looked through the archives and found that if the voltage is positive it means that the oscillator is not operating. This is what I have been trying to tell you. The oscillator is dead. Ok, good, now we have absolute proof that the oscillator is dead. Now what do I look for? There could still be something not working. The oscillator coil? There is continuity but I don't know what it's value is in micro-henries. All I know is that it's a transformer. It has two primaries for the two bands, and one secondary. The part number on the oscillator coil 2DT200 matches the number in the service data. So it is original.
: I'll keep checking the archives to see what others have done in this situation. I think that this may be a common problem. If you know what to check please let me know.
:
:Thanks,
:
:Dave
::
::Radiodoc,
:: Yes, it is positive. Pin 5 is 2.4 volts and pin 6 is 2.8 volts now. The only pins that are negative are the filament pins which are -23 volts DC with respect to the chassis. But they are 6.8 volts AC when I measure across the filament.
:: Is there something else wrong elsewhere in the set that's preventing the oscillator from working?
::
::Thanks,
::
::Dave
::
:::Radiodoc,
::: It was 2.2 volts and it wasn't minus. What would be wrong if it's positive?
::: I'm going to double check that voltage.
:::
:::Thanks,
:::
:::Dave
::::Dave,
::::
::::With the radio off did you try measuring between adjacent pins (with tube removed) to see if possibly there is an arc over between pins. You mentioned there was 2 volts on the oscillator grid. There should be a negative voltage on the oscillator grid unless you forgot to type a minus sign in front of the voltage reading you posted.
::::
::::Radiodoc
::::************
::::
:::::Marv,
::::: The connections and the voltages are quite good. But it still wont oscillate. It works and absolutely refuses to work all at the same time.
:::::
:::::Thanks,
:::::
:::::Dave
::::::Marv,
:::::: Yes they are. I measure the pin and the contact and I get the same reading from both. But I'll double check.
::::::
::::::Thanks,
::::::
::::::Dave
:::::::Dave,
:::::::You have eliminated almost everything. There is one remaining item though. Are you sure the socket/tube pin connections are firm?
:::::::
:::::::marv
:::::::
::::::::Edd,
:::::::: This oscillator is dead, dead, dead. A transistor radio will pick up nothing from it. Also, the radio works exactly the same way whether the oscillator coil is connected to the oscillator side of the tuning capacitor or not. No difference. It absolutely refuses to oscillate even though all is connected perfectly. All components are good too (except for I believe, the oscillator coil). I have more than qadruple checked the 30K, 50K, and 300 whatever ohm resistors. They are hooked up correctly. Also, the another 100pf capacitor was tried and it makes no difference. It's still dead dead dead.
:::::::: I don't quite understand what you want me to do with the B & K. But I was able to use the B & K to "tune" the radio in the CW position. The rest of the radio receives the 460 Kc perfectly. So it's ready for the oscillator/mixer circuit to work. I am getting ready to replace the oscillator coil. I think I can take one from another AC/DC set just to try it out. Can I do that? I see the that there is a B+ side (output) and the other side that connects to the oscillator side of the tuning capacitor. I think that the second I replace the oscillator coil it will work perfectly. Please correct me if I'm wrong.
:::::::: The oscillator coil has two sections on it. One is the Litz wire and the other is the enameled wire.
:::::::: I think that what you want me to do at the junction of c1 and R9 is to inject an oscillation to see if I can then tune the radio normally with its tuning capacitor.
::::::::
::::::::Thanks,
::::::::
::::::::Dave
:::::::::
:::::::::
:::::::::
:::::::::
:::::::::After reviewing your last postings info:
:::::::::My fustus “querstion” was if the radio operated in some degree of receiving stations ? via a tunable superheterodyne action / mode prior to the mass recapping of the unit ?
:::::::::
:::::::::
:::::::::
:::::::::Can we assume that C9..100 mmfd was ok and not even messed with ?
:::::::::Is cathode resistor R2 wired up ok and at its ~350 ohm value ?
:::::::::As well as the grid resistor of R1 ….50k wired properly and at its value ?
:::::::::The last item which I am sure that you did get involved with was the cathode bypass Condenser C7….05 ufd and it is OK and was reinstalled to the correct terminals…right…as that is also as critical as the 3 companion items.
:::::::::
:::::::::
:::::::::
:::::::::Looks as if the oscillator coil is on the larger ½ to ¾ in coil form and and a Litz wound unit in a tight layer…rather than the old style of enameled wire wound the full length of a long coil form. Plus, you seem to attest of its wirings continuity integrity as well as the adjunct tuning cap and its trimmer caps not being shorted out or dragging plates. Plus the additional reverting of one of the windings for a proper feed back phase check.
:::::::::Also with your BEE und KAY, you should be able to couple its input into the first grid of the mixer and at the proper injection of CW RF level, be able to swing its dial thru the 1005-2195 khc range and tune thru your stronger receptive stations in the area, with the two “TRF” stations being the powerhouses, BUT with the necessity of having to manually tune the tuning condenser in order to optimize the RF section being in resonance with them, when trying for weaker stations in bringing up received reception level..
:::::::::
:::::::::
:::::::::
:::::::::To further ease your mind about the radios oscillator sections L-C combinations , you could go to the juncture of C9 and R1 and couple in CW RF via a series / isolative ~100 pf cap and go to the same junction and tack on an anode of a 1N34 / 60 / 64 / 270 GERMANIUM diode and at its cathodes end , take a .001 cap for bypassing to ground and then meter the cathodes output via a VTVM.
:::::::::
:::::::::
:::::::::(N0…1N 914’s/4148’s/1N400oseries for this application)(Radio Shack stocks them in case you don’t have one from an oooold generation AM transistor radio chassis or from the building of a crystal set.)
:::::::::
:::::::::
:::::::::
:::::::::Then if you will power up the BEE und KAY and place in its CW mode and set the Emerson…(No power required....as this testing will be passive)…to the 1/3 lower end of the dial 700 kc ish (tuning cap ~ ¾ meshed)
:::::::::Then you tune the B & K in the ~1000-1400 range and see if the co-joined parasitic tuned oscillators circuit doesn’t give you a rising / declining reading as resonance was scanned across.
:::::::::Then, hop the radios tuning up to the higher third of the band (tuning cap ~ 1/4 meshed) and test for a like reading of a viable resonant circuit pair working at that
:::::::::frequency also.
:::::::::Thereby you have merely temp- rigged up a “po boys” grid dipper to interpret the presence of a functioning / resonating effect by the osc sections variable L-C pair and it having some degree of “Q”.
:::::::::
:::::::::
:::::::::The other alternative being that recurrent sweep Eico 460 Scope / Kluge of yours, so I think that with the former detected and metered RF , you would be much better off.
:::::::::
:::::::::
:::::::::
:::::::::Addenda:
:::::::::Noticed your new readings just at this posting time, and the bucolic local osc grid voltages reading. And have you confirmed that there is even any level oscillation by the taking of a portable xstr radios ferri-loop and placing it atop the osc coil winding and tune it off station just onto the very edge / sideband of a weaker ~1400-1740 kc AM station and then run the operating radio's tuning condenser across the bottom half of the AM band to see if even a weak heterodyning / birdie is heard on the xstr radio.
:::::::::
:::::::::Standing by for feed back
:::::::::
:::::::::
:::::::::73's de Edd
:::::::::
:::::::::
:::::::::
:::::::::
:::::::::
:::::::::
:::::::::
:::::::::
:::::::::
:::::::::
::::::::::Marv and all,
::::::::::
:::::::::: Here are the voltage readings on the 6A7 tube.
::::::::::
::::::::::Pins 1 & 7: 6.8 volts AC (Filament)
::::::::::Pin 2: 107.5 v DC (Plate)
::::::::::Pin 3: 43.5 volts DC (G3 and G5)
::::::::::Pin 4: 106.7 volts (G2)
::::::::::Pin 5: 2.2 V DC (G1)
::::::::::Pin 6: 2.647 volts DC (Cathode)
::::::::::Cap: -.361 v DC (G4)
::::::::::
::::::::::These seem like pretty healthy voltages to me. I don't see anything wrong there. The IF transformer is connecting B+ to the plate and the Oscillator coil is connecting B+ to to pin 4. So neither coil is open.
::::::::::
::::::::::I did notice that C17 was missing. I put it back and it might have made an improvement but not with the oscillator.
::::::::::
::::::::::Please if anyone has anymore ideas before I "attack" (very closely examine) the oscillator coil, please help.
::::::::::
::::::::::Thanks,
::::::::::
::::::::::Dave
::::::::::
:::::::::::Marv,
::::::::::: My RF signal generator modulates a 400 Hz tone on the 456 Kc carrier frequency when it's set to 456 Kc. The part of the radio that the signal generator is connected to is tune to exactly tuned to 456 Kc. It can receive 456 Kc and only 456 Kc. That "station" is received and I can blast the 400 Hz tone through the speaker of the radio. If I change the RF signal generator to another frequency, then no 400 Hz tone is heard. It is as perfectly aligned as I can get it. It may not have the best adjacent channel rejection but the signal is the strongest when the signal generator is set to 456 Kc.
::::::::::: The front part of the radio is what I'm having trouble with, and NOT the 456 Kc area. The radio is not converting (moving) the received frequency to 456 Kc. I can hear 570 Kc near the low end of the band and 620 Kc near the high end of the band (I live right near the brodcast antennas for these stations). That's all it does. It absolutely refuses to oscillate under any circumstances. I have checked about all I can check. All is working and not working at the same time.
::::::::::: The trimmers you are talking about are the oscillator trimmers that can only do anything, are only active, if the oscillator is working. I can put them in any position and they do nothing. They aren't shorted. They are perfectly good but not active because the oscillator is dead.
::::::::::: C-18 is brand new. It doesn't have any problems. One end is connected to the chassis and the other end is connected to a resistor. R3. I'll double check that it's also connected to the dead oscillator coil. It's not open. It just refuses to oscillate. All 11 paper and 2 electrolytic capacitors have been replaced. The positives of the electrolytic capacitors connect to the same place and the negatives connect to two different places.
::::::::::: I am getting close to removing the oscillator coil and replacing it or rewinding this one. If only I had the specs for this one. The part number on it is: 2DT200. Maybe someone has an Emerson specs book.
:::::::::::
:::::::::::Thanks,
:::::::::::
:::::::::::Dave
:::::::::::
::::::::::::Dave,
::::::::::::The oscillator has 2 trimmers in BC mode. One on the tuning cap (C-3) and the other at the rear (C-5), either of which could hamper operation if misadjusted. The one at C-3 is common to both SW and BC. Check C-18. Also, when you tested the IF, (456kHz) were you using signal levels low to moderate or high enough to blast through at any freq?
::::::::::::
::::::::::::marv
::::::::::::
:::::::::::::Marv,
::::::::::::: The resistors are the correct value. I checked them. I never replaced them. I also knew that the long black capacitor looking devices were also resistors. They are all correct. The capacitors are in the correct places. Nothing has been changed.
::::::::::::: I'll check the voltage and double check for "birdies". I think I did hear them. My huge isolation transformer is getting a lot of use on this restoration.
:::::::::::::
:::::::::::::Thanks,
:::::::::::::
:::::::::::::Dave
:::::::::::::
::::::::::::::Dave,
::::::::::::::In reading your 2 posts, I assume the set never worked and you re-capped and replaced bad resistors first. In this case, did you replace the parts just as they were originally installed, but did you also verify their placement via the schematic?
::::::::::::::
::::::::::::::marv
::::::::::::::
:::::::::::::::Radiodoc,
::::::::::::::: I just tried that and it makes absolutely no difference whatsoever.
::::::::::::::: What do I look at next?
:::::::::::::::
:::::::::::::::Thanks,
:::::::::::::::
::::::::::::::::Dave,
::::::::::::::::
::::::::::::::::The 98 volts is probably ok. If all else failed and as a shot in the dark, I would reverse the coil leads on the non-tuned winding between B+ and the oscillator "plate" and see what happens.
::::::::::::::::
::::::::::::::::Radiodoc
::::::::::::::::***************
::::::::::::::::
:::::::::::::::::Radiodoc,
::::::::::::::::: I took out the oscillator coil and checked every connection and all are good (Perfect), no opens. I checked and cleaned the band switch several times. I replaced C9 several times. When I connect 456 Kc to it from my RF signal generator, it receives that tone perfectly. It blasts!! But it wont take what's presented to it from the antenna terminals and convert that to 456 Kc. It absolutely refuses to do that under any circumstances.
::::::::::::::::: I checked all the connections and they are perfectly perfectly perfect. The resistors are all the correct values. The solder connections have been re-done and they are nice and shiny.
::::::::::::::::: I tried 3 different 6A7 tubes and none of them make any difference.
::::::::::::::::: I checked to make sure that the tuning capacitor or trimmer have any shorts on the oscillator side and there are no shorts. When the set is on and I try to adjust the oscillator screw or short the rotor with the stator on the oscillator side it makes no difference at all. All it's doing is "TRFing". The person who owns this radio MUST have the radio working immediately. I must continue working on it until it works. What do I do next? How do I convert it to a TRF receiver?
:::::::::::::::::
:::::::::::::::::Thanks,
:::::::::::::::::
:::::::::::::::::Dave
::::::::::::::::::Radiodoc,
:::::::::::::::::: B+ is 98 volts. Is that low? Shouldn't it be a little higher? I can't see any way to raise it. Filament voltage on the 6A7 is 5.3 volts.
::::::::::::::::::
::::::::::::::::::Thanks,
::::::::::::::::::
::::::::::::::::::Dave
:::::::::::::::::::Radiodoc,
::::::::::::::::::: C9 is a 100 pf capacitor. I replaced it and it made absolutely no difference.
:::::::::::::::::::
:::::::::::::::::::Dave
::::::::::::::::::::Dave,
::::::::::::::::::::
::::::::::::::::::::If all fails, walk away for a while and then come back and check carefully all the wiring around the osc circuit for correctness and good solder joints. Did you check C9 (probably a mica)or replace it. If not may try substituting another. Voltage checks on the stage may give a clue if any are off very much.
::::::::::::::::::::
::::::::::::::::::::Radiodoc
::::::::::::::::::::***********
::::::::::::::::::::
::::::::::::::::::::
:::::::::::::::::::::Hello All,
::::::::::::::::::::: I have checked everything and the oscillator absolutely refuses to work. All paper and filter capacitors have been replaced. No part of the oscillator coil is open. The resistors are good. I tried a few 6A7s and it still wont work. What to I look at next?
::::::::::::::::::::: This is an AC/DC set. There's not that much there.
:::::::::::::::::::::
:::::::::::::::::::::Thanks,
:::::::::::::::::::::
:::::::::::::::::::::Dave
C8 is brand new. It is a bypass capacitor. The old waxy one was removed from the radio about a week ago. The circuit updates don't seem to have anything to do with the oscillator. The 456 Kc part of the radio works fine.
When I attempted to look at C8, R9 (500K), in another part of the radio, fell apart. Also one of the leads fell off of a flexible resistor R2. So I had to replace them. I re-soldered the wire C8 wire to the 6A7 pin and it made absolutely no difference. The oscillator is still dead.
I do notice now that when the set is on a while, the B+ voltage goes down to 85 volts. These are brand new filter capacitors. So that cannot be the problem. I'll just have to replace every resistor, including the flexible ones. Those crimps onto the carbon must all be failing. I have tons of NOS old style resistors.
The Oscillator is still Dead Dead Dead.
I'll replace the resistors and let everyone know if the oscillator starts to work. It will probably never work. I'll also try 7 or 8 more 6A7s.
What should I look at next?
Thanks,
Dave
:Dave, I'm too slow (both ways) to keep up with this thread. But I got to wade in. C-8 is one to recheck, off the 6A7 screen. Also, just curious, did you need to make the changes to R-9, 11, & 12, and C-13 & 14 based on your serial number?
:
:Bill VA
:
:
::Radiodoc,
:: I just looked through the archives and found that if the voltage is positive it means that the oscillator is not operating. This is what I have been trying to tell you. The oscillator is dead. Ok, good, now we have absolute proof that the oscillator is dead. Now what do I look for? There could still be something not working. The oscillator coil? There is continuity but I don't know what it's value is in micro-henries. All I know is that it's a transformer. It has two primaries for the two bands, and one secondary. The part number on the oscillator coil 2DT200 matches the number in the service data. So it is original.
:: I'll keep checking the archives to see what others have done in this situation. I think that this may be a common problem. If you know what to check please let me know.
::
::Thanks,
::
::Dave
:::
:::Radiodoc,
::: Yes, it is positive. Pin 5 is 2.4 volts and pin 6 is 2.8 volts now. The only pins that are negative are the filament pins which are -23 volts DC with respect to the chassis. But they are 6.8 volts AC when I measure across the filament.
::: Is there something else wrong elsewhere in the set that's preventing the oscillator from working?
:::
:::Thanks,
:::
:::Dave
:::
::::Radiodoc,
:::: It was 2.2 volts and it wasn't minus. What would be wrong if it's positive?
:::: I'm going to double check that voltage.
::::
::::Thanks,
::::
::::Dave
:::::Dave,
:::::
:::::With the radio off did you try measuring between adjacent pins (with tube removed) to see if possibly there is an arc over between pins. You mentioned there was 2 volts on the oscillator grid. There should be a negative voltage on the oscillator grid unless you forgot to type a minus sign in front of the voltage reading you posted.
:::::
:::::Radiodoc
:::::************
:::::
::::::Marv,
:::::: The connections and the voltages are quite good. But it still wont oscillate. It works and absolutely refuses to work all at the same time.
::::::
::::::Thanks,
::::::
::::::Dave
:::::::Marv,
::::::: Yes they are. I measure the pin and the contact and I get the same reading from both. But I'll double check.
:::::::
:::::::Thanks,
:::::::
:::::::Dave
::::::::Dave,
::::::::You have eliminated almost everything. There is one remaining item though. Are you sure the socket/tube pin connections are firm?
::::::::
::::::::marv
::::::::
:::::::::Edd,
::::::::: This oscillator is dead, dead, dead. A transistor radio will pick up nothing from it. Also, the radio works exactly the same way whether the oscillator coil is connected to the oscillator side of the tuning capacitor or not. No difference. It absolutely refuses to oscillate even though all is connected perfectly. All components are good too (except for I believe, the oscillator coil). I have more than qadruple checked the 30K, 50K, and 300 whatever ohm resistors. They are hooked up correctly. Also, the another 100pf capacitor was tried and it makes no difference. It's still dead dead dead.
::::::::: I don't quite understand what you want me to do with the B & K. But I was able to use the B & K to "tune" the radio in the CW position. The rest of the radio receives the 460 Kc perfectly. So it's ready for the oscillator/mixer circuit to work. I am getting ready to replace the oscillator coil. I think I can take one from another AC/DC set just to try it out. Can I do that? I see the that there is a B+ side (output) and the other side that connects to the oscillator side of the tuning capacitor. I think that the second I replace the oscillator coil it will work perfectly. Please correct me if I'm wrong.
::::::::: The oscillator coil has two sections on it. One is the Litz wire and the other is the enameled wire.
::::::::: I think that what you want me to do at the junction of c1 and R9 is to inject an oscillation to see if I can then tune the radio normally with its tuning capacitor.
:::::::::
:::::::::Thanks,
:::::::::
:::::::::Dave
::::::::::
::::::::::
::::::::::
::::::::::
::::::::::After reviewing your last postings info:
::::::::::My fustus “querstion” was if the radio operated in some degree of receiving stations ? via a tunable superheterodyne action / mode prior to the mass recapping of the unit ?
::::::::::
::::::::::
::::::::::
::::::::::Can we assume that C9..100 mmfd was ok and not even messed with ?
::::::::::Is cathode resistor R2 wired up ok and at its ~350 ohm value ?
::::::::::As well as the grid resistor of R1 ….50k wired properly and at its value ?
::::::::::The last item which I am sure that you did get involved with was the cathode bypass Condenser C7….05 ufd and it is OK and was reinstalled to the correct terminals…right…as that is also as critical as the 3 companion items.
::::::::::
::::::::::
::::::::::
::::::::::Looks as if the oscillator coil is on the larger ½ to ¾ in coil form and and a Litz wound unit in a tight layer…rather than the old style of enameled wire wound the full length of a long coil form. Plus, you seem to attest of its wirings continuity integrity as well as the adjunct tuning cap and its trimmer caps not being shorted out or dragging plates. Plus the additional reverting of one of the windings for a proper feed back phase check.
::::::::::Also with your BEE und KAY, you should be able to couple its input into the first grid of the mixer and at the proper injection of CW RF level, be able to swing its dial thru the 1005-2195 khc range and tune thru your stronger receptive stations in the area, with the two “TRF” stations being the powerhouses, BUT with the necessity of having to manually tune the tuning condenser in order to optimize the RF section being in resonance with them, when trying for weaker stations in bringing up received reception level..
::::::::::
::::::::::
::::::::::
::::::::::To further ease your mind about the radios oscillator sections L-C combinations , you could go to the juncture of C9 and R1 and couple in CW RF via a series / isolative ~100 pf cap and go to the same junction and tack on an anode of a 1N34 / 60 / 64 / 270 GERMANIUM diode and at its cathodes end , take a .001 cap for bypassing to ground and then meter the cathodes output via a VTVM.
::::::::::
::::::::::
::::::::::(N0…1N 914’s/4148’s/1N400oseries for this application)(Radio Shack stocks them in case you don’t have one from an oooold generation AM transistor radio chassis or from the building of a crystal set.)
::::::::::
::::::::::
::::::::::
::::::::::Then if you will power up the BEE und KAY and place in its CW mode and set the Emerson…(No power required....as this testing will be passive)…to the 1/3 lower end of the dial 700 kc ish (tuning cap ~ ¾ meshed)
::::::::::Then you tune the B & K in the ~1000-1400 range and see if the co-joined parasitic tuned oscillators circuit doesn’t give you a rising / declining reading as resonance was scanned across.
::::::::::Then, hop the radios tuning up to the higher third of the band (tuning cap ~ 1/4 meshed) and test for a like reading of a viable resonant circuit pair working at that
::::::::::frequency also.
::::::::::Thereby you have merely temp- rigged up a “po boys” grid dipper to interpret the presence of a functioning / resonating effect by the osc sections variable L-C pair and it having some degree of “Q”.
::::::::::
::::::::::
::::::::::The other alternative being that recurrent sweep Eico 460 Scope / Kluge of yours, so I think that with the former detected and metered RF , you would be much better off.
::::::::::
::::::::::
::::::::::
::::::::::Addenda:
::::::::::Noticed your new readings just at this posting time, and the bucolic local osc grid voltages reading. And have you confirmed that there is even any level oscillation by the taking of a portable xstr radios ferri-loop and placing it atop the osc coil winding and tune it off station just onto the very edge / sideband of a weaker ~1400-1740 kc AM station and then run the operating radio's tuning condenser across the bottom half of the AM band to see if even a weak heterodyning / birdie is heard on the xstr radio.
::::::::::
::::::::::Standing by for feed back
::::::::::
::::::::::
::::::::::73's de Edd
::::::::::
::::::::::
::::::::::
::::::::::
::::::::::
::::::::::
::::::::::
::::::::::
::::::::::
::::::::::
:::::::::::Marv and all,
:::::::::::
::::::::::: Here are the voltage readings on the 6A7 tube.
:::::::::::
:::::::::::Pins 1 & 7: 6.8 volts AC (Filament)
:::::::::::Pin 2: 107.5 v DC (Plate)
:::::::::::Pin 3: 43.5 volts DC (G3 and G5)
:::::::::::Pin 4: 106.7 volts (G2)
:::::::::::Pin 5: 2.2 V DC (G1)
:::::::::::Pin 6: 2.647 volts DC (Cathode)
:::::::::::Cap: -.361 v DC (G4)
:::::::::::
:::::::::::These seem like pretty healthy voltages to me. I don't see anything wrong there. The IF transformer is connecting B+ to the plate and the Oscillator coil is connecting B+ to to pin 4. So neither coil is open.
:::::::::::
:::::::::::I did notice that C17 was missing. I put it back and it might have made an improvement but not with the oscillator.
:::::::::::
:::::::::::Please if anyone has anymore ideas before I "attack" (very closely examine) the oscillator coil, please help.
:::::::::::
:::::::::::Thanks,
:::::::::::
:::::::::::Dave
:::::::::::
::::::::::::Marv,
:::::::::::: My RF signal generator modulates a 400 Hz tone on the 456 Kc carrier frequency when it's set to 456 Kc. The part of the radio that the signal generator is connected to is tune to exactly tuned to 456 Kc. It can receive 456 Kc and only 456 Kc. That "station" is received and I can blast the 400 Hz tone through the speaker of the radio. If I change the RF signal generator to another frequency, then no 400 Hz tone is heard. It is as perfectly aligned as I can get it. It may not have the best adjacent channel rejection but the signal is the strongest when the signal generator is set to 456 Kc.
:::::::::::: The front part of the radio is what I'm having trouble with, and NOT the 456 Kc area. The radio is not converting (moving) the received frequency to 456 Kc. I can hear 570 Kc near the low end of the band and 620 Kc near the high end of the band (I live right near the brodcast antennas for these stations). That's all it does. It absolutely refuses to oscillate under any circumstances. I have checked about all I can check. All is working and not working at the same time.
:::::::::::: The trimmers you are talking about are the oscillator trimmers that can only do anything, are only active, if the oscillator is working. I can put them in any position and they do nothing. They aren't shorted. They are perfectly good but not active because the oscillator is dead.
:::::::::::: C-18 is brand new. It doesn't have any problems. One end is connected to the chassis and the other end is connected to a resistor. R3. I'll double check that it's also connected to the dead oscillator coil. It's not open. It just refuses to oscillate. All 11 paper and 2 electrolytic capacitors have been replaced. The positives of the electrolytic capacitors connect to the same place and the negatives connect to two different places.
:::::::::::: I am getting close to removing the oscillator coil and replacing it or rewinding this one. If only I had the specs for this one. The part number on it is: 2DT200. Maybe someone has an Emerson specs book.
::::::::::::
::::::::::::Thanks,
::::::::::::
::::::::::::Dave
::::::::::::
:::::::::::::Dave,
:::::::::::::The oscillator has 2 trimmers in BC mode. One on the tuning cap (C-3) and the other at the rear (C-5), either of which could hamper operation if misadjusted. The one at C-3 is common to both SW and BC. Check C-18. Also, when you tested the IF, (456kHz) were you using signal levels low to moderate or high enough to blast through at any freq?
:::::::::::::
:::::::::::::marv
:::::::::::::
::::::::::::::Marv,
:::::::::::::: The resistors are the correct value. I checked them. I never replaced them. I also knew that the long black capacitor looking devices were also resistors. They are all correct. The capacitors are in the correct places. Nothing has been changed.
:::::::::::::: I'll check the voltage and double check for "birdies". I think I did hear them. My huge isolation transformer is getting a lot of use on this restoration.
::::::::::::::
::::::::::::::Thanks,
::::::::::::::
::::::::::::::Dave
::::::::::::::
:::::::::::::::Dave,
:::::::::::::::In reading your 2 posts, I assume the set never worked and you re-capped and replaced bad resistors first. In this case, did you replace the parts just as they were originally installed, but did you also verify their placement via the schematic?
:::::::::::::::
:::::::::::::::marv
:::::::::::::::
::::::::::::::::Radiodoc,
:::::::::::::::: I just tried that and it makes absolutely no difference whatsoever.
:::::::::::::::: What do I look at next?
::::::::::::::::
::::::::::::::::Thanks,
::::::::::::::::
:::::::::::::::::Dave,
:::::::::::::::::
:::::::::::::::::The 98 volts is probably ok. If all else failed and as a shot in the dark, I would reverse the coil leads on the non-tuned winding between B+ and the oscillator "plate" and see what happens.
:::::::::::::::::
:::::::::::::::::Radiodoc
:::::::::::::::::***************
:::::::::::::::::
::::::::::::::::::Radiodoc,
:::::::::::::::::: I took out the oscillator coil and checked every connection and all are good (Perfect), no opens. I checked and cleaned the band switch several times. I replaced C9 several times. When I connect 456 Kc to it from my RF signal generator, it receives that tone perfectly. It blasts!! But it wont take what's presented to it from the antenna terminals and convert that to 456 Kc. It absolutely refuses to do that under any circumstances.
:::::::::::::::::: I checked all the connections and they are perfectly perfectly perfect. The resistors are all the correct values. The solder connections have been re-done and they are nice and shiny.
:::::::::::::::::: I tried 3 different 6A7 tubes and none of them make any difference.
:::::::::::::::::: I checked to make sure that the tuning capacitor or trimmer have any shorts on the oscillator side and there are no shorts. When the set is on and I try to adjust the oscillator screw or short the rotor with the stator on the oscillator side it makes no difference at all. All it's doing is "TRFing". The person who owns this radio MUST have the radio working immediately. I must continue working on it until it works. What do I do next? How do I convert it to a TRF receiver?
::::::::::::::::::
::::::::::::::::::Thanks,
::::::::::::::::::
::::::::::::::::::Dave
:::::::::::::::::::Radiodoc,
::::::::::::::::::: B+ is 98 volts. Is that low? Shouldn't it be a little higher? I can't see any way to raise it. Filament voltage on the 6A7 is 5.3 volts.
:::::::::::::::::::
:::::::::::::::::::Thanks,
:::::::::::::::::::
:::::::::::::::::::Dave
::::::::::::::::::::Radiodoc,
:::::::::::::::::::: C9 is a 100 pf capacitor. I replaced it and it made absolutely no difference.
::::::::::::::::::::
::::::::::::::::::::Dave
:::::::::::::::::::::Dave,
:::::::::::::::::::::
:::::::::::::::::::::If all fails, walk away for a while and then come back and check carefully all the wiring around the osc circuit for correctness and good solder joints. Did you check C9 (probably a mica)or replace it. If not may try substituting another. Voltage checks on the stage may give a clue if any are off very much.
:::::::::::::::::::::
:::::::::::::::::::::Radiodoc
:::::::::::::::::::::***********
:::::::::::::::::::::
:::::::::::::::::::::
::::::::::::::::::::::Hello All,
:::::::::::::::::::::: I have checked everything and the oscillator absolutely refuses to work. All paper and filter capacitors have been replaced. No part of the oscillator coil is open. The resistors are good. I tried a few 6A7s and it still wont work. What to I look at next?
:::::::::::::::::::::: This is an AC/DC set. There's not that much there.
::::::::::::::::::::::
::::::::::::::::::::::Thanks,
::::::::::::::::::::::
::::::::::::::::::::::Dave
Be sure that the large section of your oscillator coil is on the tuning condenser side, and the small section is on the grid 2 side.
You can get the circuit to work. It's the same circuit as any other radio, and all of those parts, if they are working properly, would do the same thing in any other radio.
T.
I tried another oscillator coil from another radio and it refused to oscillate as well.
Dave
:Make sure that R3 and C8 are in good condition. Sometimes that can affect oscillation. I remember that one of my Zenith portables would not oscillate after a re-wire, unless the B+ resistor to grids 3 and 5 was a bit lower, which would feed the tube more B+. I found that I was using some rather weak 1LA6 tubes (which are quite similar to the 6A7), though, and after I found a good one, the circuit worked fine as per the original design. In your case it could either be a weak tube or a faulty resistor, or perhaps a leaky condenser that is loading down the resistor.
:
:Be sure that the large section of your oscillator coil is on the tuning condenser side, and the small section is on the grid 2 side.
:
:You can get the circuit to work. It's the same circuit as any other radio, and all of those parts, if they are working properly, would do the same thing in any other radio.
:
:T.
The speaker field coil is directly across the rectifier output, and as it heats up may be the reason for B+ drop. I noticed at least one similar circuit where the equivalent of C-9 was 250uufd. Have you tried paralleling it with another 100uufd to kick this oscillator into overdrive? My basic knowledge of the pentagrid converter is limited, but as I understand it, the cathode, grid 1 & 2 should operate independently, with grid 2 referred to as oscillator anode. This of course assumes that voltage grid 1 to cathode is minus.
marv
:Bill,
: C8 is brand new. It is a bypass capacitor. The old waxy one was removed from the radio about a week ago. The circuit updates don't seem to have anything to do with the oscillator. The 456 Kc part of the radio works fine.
: When I attempted to look at C8, R9 (500K), in another part of the radio, fell apart. Also one of the leads fell off of a flexible resistor R2. So I had to replace them. I re-soldered the wire C8 wire to the 6A7 pin and it made absolutely no difference. The oscillator is still dead.
:
: I do notice now that when the set is on a while, the B+ voltage goes down to 85 volts. These are brand new filter capacitors. So that cannot be the problem. I'll just have to replace every resistor, including the flexible ones. Those crimps onto the carbon must all be failing. I have tons of NOS old style resistors.
:The Oscillator is still Dead Dead Dead.
: I'll replace the resistors and let everyone know if the oscillator starts to work. It will probably never work. I'll also try 7 or 8 more 6A7s.
: What should I look at next?
:
:Thanks,
:
:Dave
::Dave, I'm too slow (both ways) to keep up with this thread. But I got to wade in. C-8 is one to recheck, off the 6A7 screen. Also, just curious, did you need to make the changes to R-9, 11, & 12, and C-13 & 14 based on your serial number?
::
::Bill VA
::
::
:::Radiodoc,
::: I just looked through the archives and found that if the voltage is positive it means that the oscillator is not operating. This is what I have been trying to tell you. The oscillator is dead. Ok, good, now we have absolute proof that the oscillator is dead. Now what do I look for? There could still be something not working. The oscillator coil? There is continuity but I don't know what it's value is in micro-henries. All I know is that it's a transformer. It has two primaries for the two bands, and one secondary. The part number on the oscillator coil 2DT200 matches the number in the service data. So it is original.
::: I'll keep checking the archives to see what others have done in this situation. I think that this may be a common problem. If you know what to check please let me know.
:::
:::Thanks,
:::
:::Dave
::::
::::Radiodoc,
:::: Yes, it is positive. Pin 5 is 2.4 volts and pin 6 is 2.8 volts now. The only pins that are negative are the filament pins which are -23 volts DC with respect to the chassis. But they are 6.8 volts AC when I measure across the filament.
:::: Is there something else wrong elsewhere in the set that's preventing the oscillator from working?
::::
::::Thanks,
::::
::::Dave
::::
:::::Radiodoc,
::::: It was 2.2 volts and it wasn't minus. What would be wrong if it's positive?
::::: I'm going to double check that voltage.
:::::
:::::Thanks,
:::::
:::::Dave
::::::Dave,
::::::
::::::With the radio off did you try measuring between adjacent pins (with tube removed) to see if possibly there is an arc over between pins. You mentioned there was 2 volts on the oscillator grid. There should be a negative voltage on the oscillator grid unless you forgot to type a minus sign in front of the voltage reading you posted.
::::::
::::::Radiodoc
::::::************
::::::
:::::::Marv,
::::::: The connections and the voltages are quite good. But it still wont oscillate. It works and absolutely refuses to work all at the same time.
:::::::
:::::::Thanks,
:::::::
:::::::Dave
::::::::Marv,
:::::::: Yes they are. I measure the pin and the contact and I get the same reading from both. But I'll double check.
::::::::
::::::::Thanks,
::::::::
::::::::Dave
:::::::::Dave,
:::::::::You have eliminated almost everything. There is one remaining item though. Are you sure the socket/tube pin connections are firm?
:::::::::
:::::::::marv
:::::::::
::::::::::Edd,
:::::::::: This oscillator is dead, dead, dead. A transistor radio will pick up nothing from it. Also, the radio works exactly the same way whether the oscillator coil is connected to the oscillator side of the tuning capacitor or not. No difference. It absolutely refuses to oscillate even though all is connected perfectly. All components are good too (except for I believe, the oscillator coil). I have more than qadruple checked the 30K, 50K, and 300 whatever ohm resistors. They are hooked up correctly. Also, the another 100pf capacitor was tried and it makes no difference. It's still dead dead dead.
:::::::::: I don't quite understand what you want me to do with the B & K. But I was able to use the B & K to "tune" the radio in the CW position. The rest of the radio receives the 460 Kc perfectly. So it's ready for the oscillator/mixer circuit to work. I am getting ready to replace the oscillator coil. I think I can take one from another AC/DC set just to try it out. Can I do that? I see the that there is a B+ side (output) and the other side that connects to the oscillator side of the tuning capacitor. I think that the second I replace the oscillator coil it will work perfectly. Please correct me if I'm wrong.
:::::::::: The oscillator coil has two sections on it. One is the Litz wire and the other is the enameled wire.
:::::::::: I think that what you want me to do at the junction of c1 and R9 is to inject an oscillation to see if I can then tune the radio normally with its tuning capacitor.
::::::::::
::::::::::Thanks,
::::::::::
::::::::::Dave
:::::::::::
:::::::::::
:::::::::::
:::::::::::
:::::::::::After reviewing your last postings info:
:::::::::::My fustus “querstion” was if the radio operated in some degree of receiving stations ? via a tunable superheterodyne action / mode prior to the mass recapping of the unit ?
:::::::::::
:::::::::::
:::::::::::
:::::::::::Can we assume that C9..100 mmfd was ok and not even messed with ?
:::::::::::Is cathode resistor R2 wired up ok and at its ~350 ohm value ?
:::::::::::As well as the grid resistor of R1 ….50k wired properly and at its value ?
:::::::::::The last item which I am sure that you did get involved with was the cathode bypass Condenser C7….05 ufd and it is OK and was reinstalled to the correct terminals…right…as that is also as critical as the 3 companion items.
:::::::::::
:::::::::::
:::::::::::
:::::::::::Looks as if the oscillator coil is on the larger ½ to ¾ in coil form and and a Litz wound unit in a tight layer…rather than the old style of enameled wire wound the full length of a long coil form. Plus, you seem to attest of its wirings continuity integrity as well as the adjunct tuning cap and its trimmer caps not being shorted out or dragging plates. Plus the additional reverting of one of the windings for a proper feed back phase check.
:::::::::::Also with your BEE und KAY, you should be able to couple its input into the first grid of the mixer and at the proper injection of CW RF level, be able to swing its dial thru the 1005-2195 khc range and tune thru your stronger receptive stations in the area, with the two “TRF” stations being the powerhouses, BUT with the necessity of having to manually tune the tuning condenser in order to optimize the RF section being in resonance with them, when trying for weaker stations in bringing up received reception level..
:::::::::::
:::::::::::
:::::::::::
:::::::::::To further ease your mind about the radios oscillator sections L-C combinations , you could go to the juncture of C9 and R1 and couple in CW RF via a series / isolative ~100 pf cap and go to the same junction and tack on an anode of a 1N34 / 60 / 64 / 270 GERMANIUM diode and at its cathodes end , take a .001 cap for bypassing to ground and then meter the cathodes output via a VTVM.
:::::::::::
:::::::::::
:::::::::::(N0…1N 914’s/4148’s/1N400oseries for this application)(Radio Shack stocks them in case you don’t have one from an oooold generation AM transistor radio chassis or from the building of a crystal set.)
:::::::::::
:::::::::::
:::::::::::
:::::::::::Then if you will power up the BEE und KAY and place in its CW mode and set the Emerson…(No power required....as this testing will be passive)…to the 1/3 lower end of the dial 700 kc ish (tuning cap ~ ¾ meshed)
:::::::::::Then you tune the B & K in the ~1000-1400 range and see if the co-joined parasitic tuned oscillators circuit doesn’t give you a rising / declining reading as resonance was scanned across.
:::::::::::Then, hop the radios tuning up to the higher third of the band (tuning cap ~ 1/4 meshed) and test for a like reading of a viable resonant circuit pair working at that
:::::::::::frequency also.
:::::::::::Thereby you have merely temp- rigged up a “po boys” grid dipper to interpret the presence of a functioning / resonating effect by the osc sections variable L-C pair and it having some degree of “Q”.
:::::::::::
:::::::::::
:::::::::::The other alternative being that recurrent sweep Eico 460 Scope / Kluge of yours, so I think that with the former detected and metered RF , you would be much better off.
:::::::::::
:::::::::::
:::::::::::
:::::::::::Addenda:
:::::::::::Noticed your new readings just at this posting time, and the bucolic local osc grid voltages reading. And have you confirmed that there is even any level oscillation by the taking of a portable xstr radios ferri-loop and placing it atop the osc coil winding and tune it off station just onto the very edge / sideband of a weaker ~1400-1740 kc AM station and then run the operating radio's tuning condenser across the bottom half of the AM band to see if even a weak heterodyning / birdie is heard on the xstr radio.
:::::::::::
:::::::::::Standing by for feed back
:::::::::::
:::::::::::
:::::::::::73's de Edd
:::::::::::
:::::::::::
:::::::::::
:::::::::::
:::::::::::
:::::::::::
:::::::::::
:::::::::::
:::::::::::
:::::::::::
::::::::::::Marv and all,
::::::::::::
:::::::::::: Here are the voltage readings on the 6A7 tube.
::::::::::::
::::::::::::Pins 1 & 7: 6.8 volts AC (Filament)
::::::::::::Pin 2: 107.5 v DC (Plate)
::::::::::::Pin 3: 43.5 volts DC (G3 and G5)
::::::::::::Pin 4: 106.7 volts (G2)
::::::::::::Pin 5: 2.2 V DC (G1)
::::::::::::Pin 6: 2.647 volts DC (Cathode)
::::::::::::Cap: -.361 v DC (G4)
::::::::::::
::::::::::::These seem like pretty healthy voltages to me. I don't see anything wrong there. The IF transformer is connecting B+ to the plate and the Oscillator coil is connecting B+ to to pin 4. So neither coil is open.
::::::::::::
::::::::::::I did notice that C17 was missing. I put it back and it might have made an improvement but not with the oscillator.
::::::::::::
::::::::::::Please if anyone has anymore ideas before I "attack" (very closely examine) the oscillator coil, please help.
::::::::::::
::::::::::::Thanks,
::::::::::::
::::::::::::Dave
::::::::::::
:::::::::::::Marv,
::::::::::::: My RF signal generator modulates a 400 Hz tone on the 456 Kc carrier frequency when it's set to 456 Kc. The part of the radio that the signal generator is connected to is tune to exactly tuned to 456 Kc. It can receive 456 Kc and only 456 Kc. That "station" is received and I can blast the 400 Hz tone through the speaker of the radio. If I change the RF signal generator to another frequency, then no 400 Hz tone is heard. It is as perfectly aligned as I can get it. It may not have the best adjacent channel rejection but the signal is the strongest when the signal generator is set to 456 Kc.
::::::::::::: The front part of the radio is what I'm having trouble with, and NOT the 456 Kc area. The radio is not converting (moving) the received frequency to 456 Kc. I can hear 570 Kc near the low end of the band and 620 Kc near the high end of the band (I live right near the brodcast antennas for these stations). That's all it does. It absolutely refuses to oscillate under any circumstances. I have checked about all I can check. All is working and not working at the same time.
::::::::::::: The trimmers you are talking about are the oscillator trimmers that can only do anything, are only active, if the oscillator is working. I can put them in any position and they do nothing. They aren't shorted. They are perfectly good but not active because the oscillator is dead.
::::::::::::: C-18 is brand new. It doesn't have any problems. One end is connected to the chassis and the other end is connected to a resistor. R3. I'll double check that it's also connected to the dead oscillator coil. It's not open. It just refuses to oscillate. All 11 paper and 2 electrolytic capacitors have been replaced. The positives of the electrolytic capacitors connect to the same place and the negatives connect to two different places.
::::::::::::: I am getting close to removing the oscillator coil and replacing it or rewinding this one. If only I had the specs for this one. The part number on it is: 2DT200. Maybe someone has an Emerson specs book.
:::::::::::::
:::::::::::::Thanks,
:::::::::::::
:::::::::::::Dave
:::::::::::::
::::::::::::::Dave,
::::::::::::::The oscillator has 2 trimmers in BC mode. One on the tuning cap (C-3) and the other at the rear (C-5), either of which could hamper operation if misadjusted. The one at C-3 is common to both SW and BC. Check C-18. Also, when you tested the IF, (456kHz) were you using signal levels low to moderate or high enough to blast through at any freq?
::::::::::::::
::::::::::::::marv
::::::::::::::
:::::::::::::::Marv,
::::::::::::::: The resistors are the correct value. I checked them. I never replaced them. I also knew that the long black capacitor looking devices were also resistors. They are all correct. The capacitors are in the correct places. Nothing has been changed.
::::::::::::::: I'll check the voltage and double check for "birdies". I think I did hear them. My huge isolation transformer is getting a lot of use on this restoration.
:::::::::::::::
:::::::::::::::Thanks,
:::::::::::::::
:::::::::::::::Dave
:::::::::::::::
::::::::::::::::Dave,
::::::::::::::::In reading your 2 posts, I assume the set never worked and you re-capped and replaced bad resistors first. In this case, did you replace the parts just as they were originally installed, but did you also verify their placement via the schematic?
::::::::::::::::
::::::::::::::::marv
::::::::::::::::
:::::::::::::::::Radiodoc,
::::::::::::::::: I just tried that and it makes absolutely no difference whatsoever.
::::::::::::::::: What do I look at next?
:::::::::::::::::
:::::::::::::::::Thanks,
:::::::::::::::::
::::::::::::::::::Dave,
::::::::::::::::::
::::::::::::::::::The 98 volts is probably ok. If all else failed and as a shot in the dark, I would reverse the coil leads on the non-tuned winding between B+ and the oscillator "plate" and see what happens.
::::::::::::::::::
::::::::::::::::::Radiodoc
::::::::::::::::::***************
::::::::::::::::::
:::::::::::::::::::Radiodoc,
::::::::::::::::::: I took out the oscillator coil and checked every connection and all are good (Perfect), no opens. I checked and cleaned the band switch several times. I replaced C9 several times. When I connect 456 Kc to it from my RF signal generator, it receives that tone perfectly. It blasts!! But it wont take what's presented to it from the antenna terminals and convert that to 456 Kc. It absolutely refuses to do that under any circumstances.
::::::::::::::::::: I checked all the connections and they are perfectly perfectly perfect. The resistors are all the correct values. The solder connections have been re-done and they are nice and shiny.
::::::::::::::::::: I tried 3 different 6A7 tubes and none of them make any difference.
::::::::::::::::::: I checked to make sure that the tuning capacitor or trimmer have any shorts on the oscillator side and there are no shorts. When the set is on and I try to adjust the oscillator screw or short the rotor with the stator on the oscillator side it makes no difference at all. All it's doing is "TRFing". The person who owns this radio MUST have the radio working immediately. I must continue working on it until it works. What do I do next? How do I convert it to a TRF receiver?
:::::::::::::::::::
:::::::::::::::::::Thanks,
:::::::::::::::::::
:::::::::::::::::::Dave
::::::::::::::::::::Radiodoc,
:::::::::::::::::::: B+ is 98 volts. Is that low? Shouldn't it be a little higher? I can't see any way to raise it. Filament voltage on the 6A7 is 5.3 volts.
::::::::::::::::::::
::::::::::::::::::::Thanks,
::::::::::::::::::::
::::::::::::::::::::Dave
:::::::::::::::::::::Radiodoc,
::::::::::::::::::::: C9 is a 100 pf capacitor. I replaced it and it made absolutely no difference.
:::::::::::::::::::::
:::::::::::::::::::::Dave
::::::::::::::::::::::Dave,
::::::::::::::::::::::
::::::::::::::::::::::If all fails, walk away for a while and then come back and check carefully all the wiring around the osc circuit for correctness and good solder joints. Did you check C9 (probably a mica)or replace it. If not may try substituting another. Voltage checks on the stage may give a clue if any are off very much.
::::::::::::::::::::::
::::::::::::::::::::::Radiodoc
::::::::::::::::::::::***********
::::::::::::::::::::::
::::::::::::::::::::::
:::::::::::::::::::::::Hello All,
::::::::::::::::::::::: I have checked everything and the oscillator absolutely refuses to work. All paper and filter capacitors have been replaced. No part of the oscillator coil is open. The resistors are good. I tried a few 6A7s and it still wont work. What to I look at next?
::::::::::::::::::::::: This is an AC/DC set. There's not that much there.
:::::::::::::::::::::::
:::::::::::::::::::::::Thanks,
:::::::::::::::::::::::
:::::::::::::::::::::::Dave
Is it possible there could be leakage between pins in the socket? In the past I have run into problems with continuity between adjacent pins in a wafer type socket causing problems. I have also seen problems with corrosion at the circular contact area that fits around the tube pin. And a couple of times with wafer sockets I found a broken connection between the solder tab and the metal that fits around the tube pin. This was hidden from view by the wafer part of the socket that was sandwiched together.
Radiodoc
************
:Dave,
:The speaker field coil is directly across the rectifier output, and as it heats up may be the reason for B+ drop. I noticed at least one similar circuit where the equivalent of C-9 was 250uufd. Have you tried paralleling it with another 100uufd to kick this oscillator into overdrive? My basic knowledge of the pentagrid converter is limited, but as I understand it, the cathode, grid 1 & 2 should operate independently, with grid 2 referred to as oscillator anode. This of course assumes that voltage grid 1 to cathode is minus.
:
:marv
:
::Bill,
:: C8 is brand new. It is a bypass capacitor. The old waxy one was removed from the radio about a week ago. The circuit updates don't seem to have anything to do with the oscillator. The 456 Kc part of the radio works fine.
:: When I attempted to look at C8, R9 (500K), in another part of the radio, fell apart. Also one of the leads fell off of a flexible resistor R2. So I had to replace them. I re-soldered the wire C8 wire to the 6A7 pin and it made absolutely no difference. The oscillator is still dead.
::
:: I do notice now that when the set is on a while, the B+ voltage goes down to 85 volts. These are brand new filter capacitors. So that cannot be the problem. I'll just have to replace every resistor, including the flexible ones. Those crimps onto the carbon must all be failing. I have tons of NOS old style resistors.
::The Oscillator is still Dead Dead Dead.
:: I'll replace the resistors and let everyone know if the oscillator starts to work. It will probably never work. I'll also try 7 or 8 more 6A7s.
:: What should I look at next?
::
::Thanks,
::
::Dave
:::Dave, I'm too slow (both ways) to keep up with this thread. But I got to wade in. C-8 is one to recheck, off the 6A7 screen. Also, just curious, did you need to make the changes to R-9, 11, & 12, and C-13 & 14 based on your serial number?
:::
:::Bill VA
:::
:::
::::Radiodoc,
:::: I just looked through the archives and found that if the voltage is positive it means that the oscillator is not operating. This is what I have been trying to tell you. The oscillator is dead. Ok, good, now we have absolute proof that the oscillator is dead. Now what do I look for? There could still be something not working. The oscillator coil? There is continuity but I don't know what it's value is in micro-henries. All I know is that it's a transformer. It has two primaries for the two bands, and one secondary. The part number on the oscillator coil 2DT200 matches the number in the service data. So it is original.
:::: I'll keep checking the archives to see what others have done in this situation. I think that this may be a common problem. If you know what to check please let me know.
::::
::::Thanks,
::::
::::Dave
:::::
:::::Radiodoc,
::::: Yes, it is positive. Pin 5 is 2.4 volts and pin 6 is 2.8 volts now. The only pins that are negative are the filament pins which are -23 volts DC with respect to the chassis. But they are 6.8 volts AC when I measure across the filament.
::::: Is there something else wrong elsewhere in the set that's preventing the oscillator from working?
:::::
:::::Thanks,
:::::
:::::Dave
:::::
::::::Radiodoc,
:::::: It was 2.2 volts and it wasn't minus. What would be wrong if it's positive?
:::::: I'm going to double check that voltage.
::::::
::::::Thanks,
::::::
::::::Dave
:::::::Dave,
:::::::
:::::::With the radio off did you try measuring between adjacent pins (with tube removed) to see if possibly there is an arc over between pins. You mentioned there was 2 volts on the oscillator grid. There should be a negative voltage on the oscillator grid unless you forgot to type a minus sign in front of the voltage reading you posted.
:::::::
:::::::Radiodoc
:::::::************
:::::::
::::::::Marv,
:::::::: The connections and the voltages are quite good. But it still wont oscillate. It works and absolutely refuses to work all at the same time.
::::::::
::::::::Thanks,
::::::::
::::::::Dave
:::::::::Marv,
::::::::: Yes they are. I measure the pin and the contact and I get the same reading from both. But I'll double check.
:::::::::
:::::::::Thanks,
:::::::::
:::::::::Dave
::::::::::Dave,
::::::::::You have eliminated almost everything. There is one remaining item though. Are you sure the socket/tube pin connections are firm?
::::::::::
::::::::::marv
::::::::::
:::::::::::Edd,
::::::::::: This oscillator is dead, dead, dead. A transistor radio will pick up nothing from it. Also, the radio works exactly the same way whether the oscillator coil is connected to the oscillator side of the tuning capacitor or not. No difference. It absolutely refuses to oscillate even though all is connected perfectly. All components are good too (except for I believe, the oscillator coil). I have more than qadruple checked the 30K, 50K, and 300 whatever ohm resistors. They are hooked up correctly. Also, the another 100pf capacitor was tried and it makes no difference. It's still dead dead dead.
::::::::::: I don't quite understand what you want me to do with the B & K. But I was able to use the B & K to "tune" the radio in the CW position. The rest of the radio receives the 460 Kc perfectly. So it's ready for the oscillator/mixer circuit to work. I am getting ready to replace the oscillator coil. I think I can take one from another AC/DC set just to try it out. Can I do that? I see the that there is a B+ side (output) and the other side that connects to the oscillator side of the tuning capacitor. I think that the second I replace the oscillator coil it will work perfectly. Please correct me if I'm wrong.
::::::::::: The oscillator coil has two sections on it. One is the Litz wire and the other is the enameled wire.
::::::::::: I think that what you want me to do at the junction of c1 and R9 is to inject an oscillation to see if I can then tune the radio normally with its tuning capacitor.
:::::::::::
:::::::::::Thanks,
:::::::::::
:::::::::::Dave
::::::::::::
::::::::::::
::::::::::::
::::::::::::
::::::::::::After reviewing your last postings info:
::::::::::::My fustus “querstion” was if the radio operated in some degree of receiving stations ? via a tunable superheterodyne action / mode prior to the mass recapping of the unit ?
::::::::::::
::::::::::::
::::::::::::
::::::::::::Can we assume that C9..100 mmfd was ok and not even messed with ?
::::::::::::Is cathode resistor R2 wired up ok and at its ~350 ohm value ?
::::::::::::As well as the grid resistor of R1 ….50k wired properly and at its value ?
::::::::::::The last item which I am sure that you did get involved with was the cathode bypass Condenser C7….05 ufd and it is OK and was reinstalled to the correct terminals…right…as that is also as critical as the 3 companion items.
::::::::::::
::::::::::::
::::::::::::
::::::::::::Looks as if the oscillator coil is on the larger ½ to ¾ in coil form and and a Litz wound unit in a tight layer…rather than the old style of enameled wire wound the full length of a long coil form. Plus, you seem to attest of its wirings continuity integrity as well as the adjunct tuning cap and its trimmer caps not being shorted out or dragging plates. Plus the additional reverting of one of the windings for a proper feed back phase check.
::::::::::::Also with your BEE und KAY, you should be able to couple its input into the first grid of the mixer and at the proper injection of CW RF level, be able to swing its dial thru the 1005-2195 khc range and tune thru your stronger receptive stations in the area, with the two “TRF” stations being the powerhouses, BUT with the necessity of having to manually tune the tuning condenser in order to optimize the RF section being in resonance with them, when trying for weaker stations in bringing up received reception level..
::::::::::::
::::::::::::
::::::::::::
::::::::::::To further ease your mind about the radios oscillator sections L-C combinations , you could go to the juncture of C9 and R1 and couple in CW RF via a series / isolative ~100 pf cap and go to the same junction and tack on an anode of a 1N34 / 60 / 64 / 270 GERMANIUM diode and at its cathodes end , take a .001 cap for bypassing to ground and then meter the cathodes output via a VTVM.
::::::::::::
::::::::::::
::::::::::::(N0…1N 914’s/4148’s/1N400oseries for this application)(Radio Shack stocks them in case you don’t have one from an oooold generation AM transistor radio chassis or from the building of a crystal set.)
::::::::::::
::::::::::::
::::::::::::
::::::::::::Then if you will power up the BEE und KAY and place in its CW mode and set the Emerson…(No power required....as this testing will be passive)…to the 1/3 lower end of the dial 700 kc ish (tuning cap ~ ¾ meshed)
::::::::::::Then you tune the B & K in the ~1000-1400 range and see if the co-joined parasitic tuned oscillators circuit doesn’t give you a rising / declining reading as resonance was scanned across.
::::::::::::Then, hop the radios tuning up to the higher third of the band (tuning cap ~ 1/4 meshed) and test for a like reading of a viable resonant circuit pair working at that
::::::::::::frequency also.
::::::::::::Thereby you have merely temp- rigged up a “po boys” grid dipper to interpret the presence of a functioning / resonating effect by the osc sections variable L-C pair and it having some degree of “Q”.
::::::::::::
::::::::::::
::::::::::::The other alternative being that recurrent sweep Eico 460 Scope / Kluge of yours, so I think that with the former detected and metered RF , you would be much better off.
::::::::::::
::::::::::::
::::::::::::
::::::::::::Addenda:
::::::::::::Noticed your new readings just at this posting time, and the bucolic local osc grid voltages reading. And have you confirmed that there is even any level oscillation by the taking of a portable xstr radios ferri-loop and placing it atop the osc coil winding and tune it off station just onto the very edge / sideband of a weaker ~1400-1740 kc AM station and then run the operating radio's tuning condenser across the bottom half of the AM band to see if even a weak heterodyning / birdie is heard on the xstr radio.
::::::::::::
::::::::::::Standing by for feed back
::::::::::::
::::::::::::
::::::::::::73's de Edd
::::::::::::
::::::::::::
::::::::::::
::::::::::::
::::::::::::
::::::::::::
::::::::::::
::::::::::::
::::::::::::
::::::::::::
:::::::::::::Marv and all,
:::::::::::::
::::::::::::: Here are the voltage readings on the 6A7 tube.
:::::::::::::
:::::::::::::Pins 1 & 7: 6.8 volts AC (Filament)
:::::::::::::Pin 2: 107.5 v DC (Plate)
:::::::::::::Pin 3: 43.5 volts DC (G3 and G5)
:::::::::::::Pin 4: 106.7 volts (G2)
:::::::::::::Pin 5: 2.2 V DC (G1)
:::::::::::::Pin 6: 2.647 volts DC (Cathode)
:::::::::::::Cap: -.361 v DC (G4)
:::::::::::::
:::::::::::::These seem like pretty healthy voltages to me. I don't see anything wrong there. The IF transformer is connecting B+ to the plate and the Oscillator coil is connecting B+ to to pin 4. So neither coil is open.
:::::::::::::
:::::::::::::I did notice that C17 was missing. I put it back and it might have made an improvement but not with the oscillator.
:::::::::::::
:::::::::::::Please if anyone has anymore ideas before I "attack" (very closely examine) the oscillator coil, please help.
:::::::::::::
:::::::::::::Thanks,
:::::::::::::
:::::::::::::Dave
:::::::::::::
::::::::::::::Marv,
:::::::::::::: My RF signal generator modulates a 400 Hz tone on the 456 Kc carrier frequency when it's set to 456 Kc. The part of the radio that the signal generator is connected to is tune to exactly tuned to 456 Kc. It can receive 456 Kc and only 456 Kc. That "station" is received and I can blast the 400 Hz tone through the speaker of the radio. If I change the RF signal generator to another frequency, then no 400 Hz tone is heard. It is as perfectly aligned as I can get it. It may not have the best adjacent channel rejection but the signal is the strongest when the signal generator is set to 456 Kc.
:::::::::::::: The front part of the radio is what I'm having trouble with, and NOT the 456 Kc area. The radio is not converting (moving) the received frequency to 456 Kc. I can hear 570 Kc near the low end of the band and 620 Kc near the high end of the band (I live right near the brodcast antennas for these stations). That's all it does. It absolutely refuses to oscillate under any circumstances. I have checked about all I can check. All is working and not working at the same time.
:::::::::::::: The trimmers you are talking about are the oscillator trimmers that can only do anything, are only active, if the oscillator is working. I can put them in any position and they do nothing. They aren't shorted. They are perfectly good but not active because the oscillator is dead.
:::::::::::::: C-18 is brand new. It doesn't have any problems. One end is connected to the chassis and the other end is connected to a resistor. R3. I'll double check that it's also connected to the dead oscillator coil. It's not open. It just refuses to oscillate. All 11 paper and 2 electrolytic capacitors have been replaced. The positives of the electrolytic capacitors connect to the same place and the negatives connect to two different places.
:::::::::::::: I am getting close to removing the oscillator coil and replacing it or rewinding this one. If only I had the specs for this one. The part number on it is: 2DT200. Maybe someone has an Emerson specs book.
::::::::::::::
::::::::::::::Thanks,
::::::::::::::
::::::::::::::Dave
::::::::::::::
:::::::::::::::Dave,
:::::::::::::::The oscillator has 2 trimmers in BC mode. One on the tuning cap (C-3) and the other at the rear (C-5), either of which could hamper operation if misadjusted. The one at C-3 is common to both SW and BC. Check C-18. Also, when you tested the IF, (456kHz) were you using signal levels low to moderate or high enough to blast through at any freq?
:::::::::::::::
:::::::::::::::marv
:::::::::::::::
::::::::::::::::Marv,
:::::::::::::::: The resistors are the correct value. I checked them. I never replaced them. I also knew that the long black capacitor looking devices were also resistors. They are all correct. The capacitors are in the correct places. Nothing has been changed.
:::::::::::::::: I'll check the voltage and double check for "birdies". I think I did hear them. My huge isolation transformer is getting a lot of use on this restoration.
::::::::::::::::
::::::::::::::::Thanks,
::::::::::::::::
::::::::::::::::Dave
::::::::::::::::
:::::::::::::::::Dave,
:::::::::::::::::In reading your 2 posts, I assume the set never worked and you re-capped and replaced bad resistors first. In this case, did you replace the parts just as they were originally installed, but did you also verify their placement via the schematic?
:::::::::::::::::
:::::::::::::::::marv
:::::::::::::::::
::::::::::::::::::Radiodoc,
:::::::::::::::::: I just tried that and it makes absolutely no difference whatsoever.
:::::::::::::::::: What do I look at next?
::::::::::::::::::
::::::::::::::::::Thanks,
::::::::::::::::::
:::::::::::::::::::Dave,
:::::::::::::::::::
:::::::::::::::::::The 98 volts is probably ok. If all else failed and as a shot in the dark, I would reverse the coil leads on the non-tuned winding between B+ and the oscillator "plate" and see what happens.
:::::::::::::::::::
:::::::::::::::::::Radiodoc
:::::::::::::::::::***************
:::::::::::::::::::
::::::::::::::::::::Radiodoc,
:::::::::::::::::::: I took out the oscillator coil and checked every connection and all are good (Perfect), no opens. I checked and cleaned the band switch several times. I replaced C9 several times. When I connect 456 Kc to it from my RF signal generator, it receives that tone perfectly. It blasts!! But it wont take what's presented to it from the antenna terminals and convert that to 456 Kc. It absolutely refuses to do that under any circumstances.
:::::::::::::::::::: I checked all the connections and they are perfectly perfectly perfect. The resistors are all the correct values. The solder connections have been re-done and they are nice and shiny.
:::::::::::::::::::: I tried 3 different 6A7 tubes and none of them make any difference.
:::::::::::::::::::: I checked to make sure that the tuning capacitor or trimmer have any shorts on the oscillator side and there are no shorts. When the set is on and I try to adjust the oscillator screw or short the rotor with the stator on the oscillator side it makes no difference at all. All it's doing is "TRFing". The person who owns this radio MUST have the radio working immediately. I must continue working on it until it works. What do I do next? How do I convert it to a TRF receiver?
::::::::::::::::::::
::::::::::::::::::::Thanks,
::::::::::::::::::::
::::::::::::::::::::Dave
:::::::::::::::::::::Radiodoc,
::::::::::::::::::::: B+ is 98 volts. Is that low? Shouldn't it be a little higher? I can't see any way to raise it. Filament voltage on the 6A7 is 5.3 volts.
:::::::::::::::::::::
:::::::::::::::::::::Thanks,
:::::::::::::::::::::
:::::::::::::::::::::Dave
::::::::::::::::::::::Radiodoc,
:::::::::::::::::::::: C9 is a 100 pf capacitor. I replaced it and it made absolutely no difference.
::::::::::::::::::::::
::::::::::::::::::::::Dave
:::::::::::::::::::::::Dave,
:::::::::::::::::::::::
:::::::::::::::::::::::If all fails, walk away for a while and then come back and check carefully all the wiring around the osc circuit for correctness and good solder joints. Did you check C9 (probably a mica)or replace it. If not may try substituting another. Voltage checks on the stage may give a clue if any are off very much.
:::::::::::::::::::::::
:::::::::::::::::::::::Radiodoc
:::::::::::::::::::::::***********
:::::::::::::::::::::::
:::::::::::::::::::::::
::::::::::::::::::::::::Hello All,
:::::::::::::::::::::::: I have checked everything and the oscillator absolutely refuses to work. All paper and filter capacitors have been replaced. No part of the oscillator coil is open. The resistors are good. I tried a few 6A7s and it still wont work. What to I look at next?
:::::::::::::::::::::::: This is an AC/DC set. There's not that much there.
::::::::::::::::::::::::
::::::::::::::::::::::::Thanks,
::::::::::::::::::::::::
::::::::::::::::::::::::Dave
With the tube out of the socket. I have measured between pins and from the pin to the terminal. Pins are connected to terminals perfectly. There are no broken connections. I have measured between pins and no pin is connected to any other pin. There is infinite resistance between pins. I don't think that there's anything wrong with the tube socket.
Thanks,
Dave
:Dave,
:
:Is it possible there could be leakage between pins in the socket? In the past I have run into problems with continuity between adjacent pins in a wafer type socket causing problems. I have also seen problems with corrosion at the circular contact area that fits around the tube pin. And a couple of times with wafer sockets I found a broken connection between the solder tab and the metal that fits around the tube pin. This was hidden from view by the wafer part of the socket that was sandwiched together.
:
:Radiodoc
:************
:
::Dave,
::The speaker field coil is directly across the rectifier output, and as it heats up may be the reason for B+ drop. I noticed at least one similar circuit where the equivalent of C-9 was 250uufd. Have you tried paralleling it with another 100uufd to kick this oscillator into overdrive? My basic knowledge of the pentagrid converter is limited, but as I understand it, the cathode, grid 1 & 2 should operate independently, with grid 2 referred to as oscillator anode. This of course assumes that voltage grid 1 to cathode is minus.
::
::marv
::
:::Bill,
::: C8 is brand new. It is a bypass capacitor. The old waxy one was removed from the radio about a week ago. The circuit updates don't seem to have anything to do with the oscillator. The 456 Kc part of the radio works fine.
::: When I attempted to look at C8, R9 (500K), in another part of the radio, fell apart. Also one of the leads fell off of a flexible resistor R2. So I had to replace them. I re-soldered the wire C8 wire to the 6A7 pin and it made absolutely no difference. The oscillator is still dead.
:::
::: I do notice now that when the set is on a while, the B+ voltage goes down to 85 volts. These are brand new filter capacitors. So that cannot be the problem. I'll just have to replace every resistor, including the flexible ones. Those crimps onto the carbon must all be failing. I have tons of NOS old style resistors.
:::The Oscillator is still Dead Dead Dead.
::: I'll replace the resistors and let everyone know if the oscillator starts to work. It will probably never work. I'll also try 7 or 8 more 6A7s.
::: What should I look at next?
:::
:::Thanks,
:::
:::Dave
::::Dave, I'm too slow (both ways) to keep up with this thread. But I got to wade in. C-8 is one to recheck, off the 6A7 screen. Also, just curious, did you need to make the changes to R-9, 11, & 12, and C-13 & 14 based on your serial number?
::::
::::Bill VA
::::
::::
:::::Radiodoc,
::::: I just looked through the archives and found that if the voltage is positive it means that the oscillator is not operating. This is what I have been trying to tell you. The oscillator is dead. Ok, good, now we have absolute proof that the oscillator is dead. Now what do I look for? There could still be something not working. The oscillator coil? There is continuity but I don't know what it's value is in micro-henries. All I know is that it's a transformer. It has two primaries for the two bands, and one secondary. The part number on the oscillator coil 2DT200 matches the number in the service data. So it is original.
::::: I'll keep checking the archives to see what others have done in this situation. I think that this may be a common problem. If you know what to check please let me know.
:::::
:::::Thanks,
:::::
:::::Dave
::::::
::::::Radiodoc,
:::::: Yes, it is positive. Pin 5 is 2.4 volts and pin 6 is 2.8 volts now. The only pins that are negative are the filament pins which are -23 volts DC with respect to the chassis. But they are 6.8 volts AC when I measure across the filament.
:::::: Is there something else wrong elsewhere in the set that's preventing the oscillator from working?
::::::
::::::Thanks,
::::::
::::::Dave
::::::
:::::::Radiodoc,
::::::: It was 2.2 volts and it wasn't minus. What would be wrong if it's positive?
::::::: I'm going to double check that voltage.
:::::::
:::::::Thanks,
:::::::
:::::::Dave
::::::::Dave,
::::::::
::::::::With the radio off did you try measuring between adjacent pins (with tube removed) to see if possibly there is an arc over between pins. You mentioned there was 2 volts on the oscillator grid. There should be a negative voltage on the oscillator grid unless you forgot to type a minus sign in front of the voltage reading you posted.
::::::::
::::::::Radiodoc
::::::::************
::::::::
:::::::::Marv,
::::::::: The connections and the voltages are quite good. But it still wont oscillate. It works and absolutely refuses to work all at the same time.
:::::::::
:::::::::Thanks,
:::::::::
:::::::::Dave
::::::::::Marv,
:::::::::: Yes they are. I measure the pin and the contact and I get the same reading from both. But I'll double check.
::::::::::
::::::::::Thanks,
::::::::::
::::::::::Dave
:::::::::::Dave,
:::::::::::You have eliminated almost everything. There is one remaining item though. Are you sure the socket/tube pin connections are firm?
:::::::::::
:::::::::::marv
:::::::::::
::::::::::::Edd,
:::::::::::: This oscillator is dead, dead, dead. A transistor radio will pick up nothing from it. Also, the radio works exactly the same way whether the oscillator coil is connected to the oscillator side of the tuning capacitor or not. No difference. It absolutely refuses to oscillate even though all is connected perfectly. All components are good too (except for I believe, the oscillator coil). I have more than qadruple checked the 30K, 50K, and 300 whatever ohm resistors. They are hooked up correctly. Also, the another 100pf capacitor was tried and it makes no difference. It's still dead dead dead.
:::::::::::: I don't quite understand what you want me to do with the B & K. But I was able to use the B & K to "tune" the radio in the CW position. The rest of the radio receives the 460 Kc perfectly. So it's ready for the oscillator/mixer circuit to work. I am getting ready to replace the oscillator coil. I think I can take one from another AC/DC set just to try it out. Can I do that? I see the that there is a B+ side (output) and the other side that connects to the oscillator side of the tuning capacitor. I think that the second I replace the oscillator coil it will work perfectly. Please correct me if I'm wrong.
:::::::::::: The oscillator coil has two sections on it. One is the Litz wire and the other is the enameled wire.
:::::::::::: I think that what you want me to do at the junction of c1 and R9 is to inject an oscillation to see if I can then tune the radio normally with its tuning capacitor.
::::::::::::
::::::::::::Thanks,
::::::::::::
::::::::::::Dave
:::::::::::::
:::::::::::::
:::::::::::::
:::::::::::::
:::::::::::::After reviewing your last postings info:
:::::::::::::My fustus “querstion” was if the radio operated in some degree of receiving stations ? via a tunable superheterodyne action / mode prior to the mass recapping of the unit ?
:::::::::::::
:::::::::::::
:::::::::::::
:::::::::::::Can we assume that C9..100 mmfd was ok and not even messed with ?
:::::::::::::Is cathode resistor R2 wired up ok and at its ~350 ohm value ?
:::::::::::::As well as the grid resistor of R1 ….50k wired properly and at its value ?
:::::::::::::The last item which I am sure that you did get involved with was the cathode bypass Condenser C7….05 ufd and it is OK and was reinstalled to the correct terminals…right…as that is also as critical as the 3 companion items.
:::::::::::::
:::::::::::::
:::::::::::::
:::::::::::::Looks as if the oscillator coil is on the larger ½ to ¾ in coil form and and a Litz wound unit in a tight layer…rather than the old style of enameled wire wound the full length of a long coil form. Plus, you seem to attest of its wirings continuity integrity as well as the adjunct tuning cap and its trimmer caps not being shorted out or dragging plates. Plus the additional reverting of one of the windings for a proper feed back phase check.
:::::::::::::Also with your BEE und KAY, you should be able to couple its input into the first grid of the mixer and at the proper injection of CW RF level, be able to swing its dial thru the 1005-2195 khc range and tune thru your stronger receptive stations in the area, with the two “TRF” stations being the powerhouses, BUT with the necessity of having to manually tune the tuning condenser in order to optimize the RF section being in resonance with them, when trying for weaker stations in bringing up received reception level..
:::::::::::::
:::::::::::::
:::::::::::::
:::::::::::::To further ease your mind about the radios oscillator sections L-C combinations , you could go to the juncture of C9 and R1 and couple in CW RF via a series / isolative ~100 pf cap and go to the same junction and tack on an anode of a 1N34 / 60 / 64 / 270 GERMANIUM diode and at its cathodes end , take a .001 cap for bypassing to ground and then meter the cathodes output via a VTVM.
:::::::::::::
:::::::::::::
:::::::::::::(N0…1N 914’s/4148’s/1N400oseries for this application)(Radio Shack stocks them in case you don’t have one from an oooold generation AM transistor radio chassis or from the building of a crystal set.)
:::::::::::::
:::::::::::::
:::::::::::::
:::::::::::::Then if you will power up the BEE und KAY and place in its CW mode and set the Emerson…(No power required....as this testing will be passive)…to the 1/3 lower end of the dial 700 kc ish (tuning cap ~ ¾ meshed)
:::::::::::::Then you tune the B & K in the ~1000-1400 range and see if the co-joined parasitic tuned oscillators circuit doesn’t give you a rising / declining reading as resonance was scanned across.
:::::::::::::Then, hop the radios tuning up to the higher third of the band (tuning cap ~ 1/4 meshed) and test for a like reading of a viable resonant circuit pair working at that
:::::::::::::frequency also.
:::::::::::::Thereby you have merely temp- rigged up a “po boys” grid dipper to interpret the presence of a functioning / resonating effect by the osc sections variable L-C pair and it having some degree of “Q”.
:::::::::::::
:::::::::::::
:::::::::::::The other alternative being that recurrent sweep Eico 460 Scope / Kluge of yours, so I think that with the former detected and metered RF , you would be much better off.
:::::::::::::
:::::::::::::
:::::::::::::
:::::::::::::Addenda:
:::::::::::::Noticed your new readings just at this posting time, and the bucolic local osc grid voltages reading. And have you confirmed that there is even any level oscillation by the taking of a portable xstr radios ferri-loop and placing it atop the osc coil winding and tune it off station just onto the very edge / sideband of a weaker ~1400-1740 kc AM station and then run the operating radio's tuning condenser across the bottom half of the AM band to see if even a weak heterodyning / birdie is heard on the xstr radio.
:::::::::::::
:::::::::::::Standing by for feed back
:::::::::::::
:::::::::::::
:::::::::::::73's de Edd
:::::::::::::
:::::::::::::
:::::::::::::
:::::::::::::
:::::::::::::
:::::::::::::
:::::::::::::
:::::::::::::
:::::::::::::
:::::::::::::
::::::::::::::Marv and all,
::::::::::::::
:::::::::::::: Here are the voltage readings on the 6A7 tube.
::::::::::::::
::::::::::::::Pins 1 & 7: 6.8 volts AC (Filament)
::::::::::::::Pin 2: 107.5 v DC (Plate)
::::::::::::::Pin 3: 43.5 volts DC (G3 and G5)
::::::::::::::Pin 4: 106.7 volts (G2)
::::::::::::::Pin 5: 2.2 V DC (G1)
::::::::::::::Pin 6: 2.647 volts DC (Cathode)
::::::::::::::Cap: -.361 v DC (G4)
::::::::::::::
::::::::::::::These seem like pretty healthy voltages to me. I don't see anything wrong there. The IF transformer is connecting B+ to the plate and the Oscillator coil is connecting B+ to to pin 4. So neither coil is open.
::::::::::::::
::::::::::::::I did notice that C17 was missing. I put it back and it might have made an improvement but not with the oscillator.
::::::::::::::
::::::::::::::Please if anyone has anymore ideas before I "attack" (very closely examine) the oscillator coil, please help.
::::::::::::::
::::::::::::::Thanks,
::::::::::::::
::::::::::::::Dave
::::::::::::::
:::::::::::::::Marv,
::::::::::::::: My RF signal generator modulates a 400 Hz tone on the 456 Kc carrier frequency when it's set to 456 Kc. The part of the radio that the signal generator is connected to is tune to exactly tuned to 456 Kc. It can receive 456 Kc and only 456 Kc. That "station" is received and I can blast the 400 Hz tone through the speaker of the radio. If I change the RF signal generator to another frequency, then no 400 Hz tone is heard. It is as perfectly aligned as I can get it. It may not have the best adjacent channel rejection but the signal is the strongest when the signal generator is set to 456 Kc.
::::::::::::::: The front part of the radio is what I'm having trouble with, and NOT the 456 Kc area. The radio is not converting (moving) the received frequency to 456 Kc. I can hear 570 Kc near the low end of the band and 620 Kc near the high end of the band (I live right near the brodcast antennas for these stations). That's all it does. It absolutely refuses to oscillate under any circumstances. I have checked about all I can check. All is working and not working at the same time.
::::::::::::::: The trimmers you are talking about are the oscillator trimmers that can only do anything, are only active, if the oscillator is working. I can put them in any position and they do nothing. They aren't shorted. They are perfectly good but not active because the oscillator is dead.
::::::::::::::: C-18 is brand new. It doesn't have any problems. One end is connected to the chassis and the other end is connected to a resistor. R3. I'll double check that it's also connected to the dead oscillator coil. It's not open. It just refuses to oscillate. All 11 paper and 2 electrolytic capacitors have been replaced. The positives of the electrolytic capacitors connect to the same place and the negatives connect to two different places.
::::::::::::::: I am getting close to removing the oscillator coil and replacing it or rewinding this one. If only I had the specs for this one. The part number on it is: 2DT200. Maybe someone has an Emerson specs book.
:::::::::::::::
:::::::::::::::Thanks,
:::::::::::::::
:::::::::::::::Dave
:::::::::::::::
::::::::::::::::Dave,
::::::::::::::::The oscillator has 2 trimmers in BC mode. One on the tuning cap (C-3) and the other at the rear (C-5), either of which could hamper operation if misadjusted. The one at C-3 is common to both SW and BC. Check C-18. Also, when you tested the IF, (456kHz) were you using signal levels low to moderate or high enough to blast through at any freq?
::::::::::::::::
::::::::::::::::marv
::::::::::::::::
:::::::::::::::::Marv,
::::::::::::::::: The resistors are the correct value. I checked them. I never replaced them. I also knew that the long black capacitor looking devices were also resistors. They are all correct. The capacitors are in the correct places. Nothing has been changed.
::::::::::::::::: I'll check the voltage and double check for "birdies". I think I did hear them. My huge isolation transformer is getting a lot of use on this restoration.
:::::::::::::::::
:::::::::::::::::Thanks,
:::::::::::::::::
:::::::::::::::::Dave
:::::::::::::::::
::::::::::::::::::Dave,
::::::::::::::::::In reading your 2 posts, I assume the set never worked and you re-capped and replaced bad resistors first. In this case, did you replace the parts just as they were originally installed, but did you also verify their placement via the schematic?
::::::::::::::::::
::::::::::::::::::marv
::::::::::::::::::
:::::::::::::::::::Radiodoc,
::::::::::::::::::: I just tried that and it makes absolutely no difference whatsoever.
::::::::::::::::::: What do I look at next?
:::::::::::::::::::
:::::::::::::::::::Thanks,
:::::::::::::::::::
::::::::::::::::::::Dave,
::::::::::::::::::::
::::::::::::::::::::The 98 volts is probably ok. If all else failed and as a shot in the dark, I would reverse the coil leads on the non-tuned winding between B+ and the oscillator "plate" and see what happens.
::::::::::::::::::::
::::::::::::::::::::Radiodoc
::::::::::::::::::::***************
::::::::::::::::::::
:::::::::::::::::::::Radiodoc,
::::::::::::::::::::: I took out the oscillator coil and checked every connection and all are good (Perfect), no opens. I checked and cleaned the band switch several times. I replaced C9 several times. When I connect 456 Kc to it from my RF signal generator, it receives that tone perfectly. It blasts!! But it wont take what's presented to it from the antenna terminals and convert that to 456 Kc. It absolutely refuses to do that under any circumstances.
::::::::::::::::::::: I checked all the connections and they are perfectly perfectly perfect. The resistors are all the correct values. The solder connections have been re-done and they are nice and shiny.
::::::::::::::::::::: I tried 3 different 6A7 tubes and none of them make any difference.
::::::::::::::::::::: I checked to make sure that the tuning capacitor or trimmer have any shorts on the oscillator side and there are no shorts. When the set is on and I try to adjust the oscillator screw or short the rotor with the stator on the oscillator side it makes no difference at all. All it's doing is "TRFing". The person who owns this radio MUST have the radio working immediately. I must continue working on it until it works. What do I do next? How do I convert it to a TRF receiver?
:::::::::::::::::::::
:::::::::::::::::::::Thanks,
:::::::::::::::::::::
:::::::::::::::::::::Dave
::::::::::::::::::::::Radiodoc,
:::::::::::::::::::::: B+ is 98 volts. Is that low? Shouldn't it be a little higher? I can't see any way to raise it. Filament voltage on the 6A7 is 5.3 volts.
::::::::::::::::::::::
::::::::::::::::::::::Thanks,
::::::::::::::::::::::
::::::::::::::::::::::Dave
:::::::::::::::::::::::Radiodoc,
::::::::::::::::::::::: C9 is a 100 pf capacitor. I replaced it and it made absolutely no difference.
:::::::::::::::::::::::
:::::::::::::::::::::::Dave
::::::::::::::::::::::::Dave,
::::::::::::::::::::::::
::::::::::::::::::::::::If all fails, walk away for a while and then come back and check carefully all the wiring around the osc circuit for correctness and good solder joints. Did you check C9 (probably a mica)or replace it. If not may try substituting another. Voltage checks on the stage may give a clue if any are off very much.
::::::::::::::::::::::::
::::::::::::::::::::::::Radiodoc
::::::::::::::::::::::::***********
::::::::::::::::::::::::
::::::::::::::::::::::::
:::::::::::::::::::::::::Hello All,
::::::::::::::::::::::::: I have checked everything and the oscillator absolutely refuses to work. All paper and filter capacitors have been replaced. No part of the oscillator coil is open. The resistors are good. I tried a few 6A7s and it still wont work. What to I look at next?
::::::::::::::::::::::::: This is an AC/DC set. There's not that much there.
:::::::::::::::::::::::::
:::::::::::::::::::::::::Thanks,
:::::::::::::::::::::::::
:::::::::::::::::::::::::Dave
Bill VA
:Bill,
: C8 is brand new. It is a bypass capacitor. The old waxy one was removed from the radio about a week ago. The circuit updates don't seem to have anything to do with the oscillator. The 456 Kc part of the radio works fine.
: When I attempted to look at C8, R9 (500K), in another part of the radio, fell apart. Also one of the leads fell off of a flexible resistor R2. So I had to replace them. I re-soldered the wire C8 wire to the 6A7 pin and it made absolutely no difference. The oscillator is still dead.
:
: I do notice now that when the set is on a while, the B+ voltage goes down to 85 volts. These are brand new filter capacitors. So that cannot be the problem. I'll just have to replace every resistor, including the flexible ones. Those crimps onto the carbon must all be failing. I have tons of NOS old style resistors.
:The Oscillator is still Dead Dead Dead.
: I'll replace the resistors and let everyone know if the oscillator starts to work. It will probably never work. I'll also try 7 or 8 more 6A7s.
: What should I look at next?
:
:Thanks,
:
:Dave
::Dave, I'm too slow (both ways) to keep up with this thread. But I got to wade in. C-8 is one to recheck, off the 6A7 screen. Also, just curious, did you need to make the changes to R-9, 11, & 12, and C-13 & 14 based on your serial number?
::
::Bill VA
::
::
:::Radiodoc,
::: I just looked through the archives and found that if the voltage is positive it means that the oscillator is not operating. This is what I have been trying to tell you. The oscillator is dead. Ok, good, now we have absolute proof that the oscillator is dead. Now what do I look for? There could still be something not working. The oscillator coil? There is continuity but I don't know what it's value is in micro-henries. All I know is that it's a transformer. It has two primaries for the two bands, and one secondary. The part number on the oscillator coil 2DT200 matches the number in the service data. So it is original.
::: I'll keep checking the archives to see what others have done in this situation. I think that this may be a common problem. If you know what to check please let me know.
:::
:::Thanks,
:::
:::Dave
::::
::::Radiodoc,
:::: Yes, it is positive. Pin 5 is 2.4 volts and pin 6 is 2.8 volts now. The only pins that are negative are the filament pins which are -23 volts DC with respect to the chassis. But they are 6.8 volts AC when I measure across the filament.
:::: Is there something else wrong elsewhere in the set that's preventing the oscillator from working?
::::
::::Thanks,
::::
::::Dave
::::
:::::Radiodoc,
::::: It was 2.2 volts and it wasn't minus. What would be wrong if it's positive?
::::: I'm going to double check that voltage.
:::::
:::::Thanks,
:::::
:::::Dave
::::::Dave,
::::::
::::::With the radio off did you try measuring between adjacent pins (with tube removed) to see if possibly there is an arc over between pins. You mentioned there was 2 volts on the oscillator grid. There should be a negative voltage on the oscillator grid unless you forgot to type a minus sign in front of the voltage reading you posted.
::::::
::::::Radiodoc
::::::************
::::::
:::::::Marv,
::::::: The connections and the voltages are quite good. But it still wont oscillate. It works and absolutely refuses to work all at the same time.
:::::::
:::::::Thanks,
:::::::
:::::::Dave
::::::::Marv,
:::::::: Yes they are. I measure the pin and the contact and I get the same reading from both. But I'll double check.
::::::::
::::::::Thanks,
::::::::
::::::::Dave
:::::::::Dave,
:::::::::You have eliminated almost everything. There is one remaining item though. Are you sure the socket/tube pin connections are firm?
:::::::::
:::::::::marv
:::::::::
::::::::::Edd,
:::::::::: This oscillator is dead, dead, dead. A transistor radio will pick up nothing from it. Also, the radio works exactly the same way whether the oscillator coil is connected to the oscillator side of the tuning capacitor or not. No difference. It absolutely refuses to oscillate even though all is connected perfectly. All components are good too (except for I believe, the oscillator coil). I have more than qadruple checked the 30K, 50K, and 300 whatever ohm resistors. They are hooked up correctly. Also, the another 100pf capacitor was tried and it makes no difference. It's still dead dead dead.
:::::::::: I don't quite understand what you want me to do with the B & K. But I was able to use the B & K to "tune" the radio in the CW position. The rest of the radio receives the 460 Kc perfectly. So it's ready for the oscillator/mixer circuit to work. I am getting ready to replace the oscillator coil. I think I can take one from another AC/DC set just to try it out. Can I do that? I see the that there is a B+ side (output) and the other side that connects to the oscillator side of the tuning capacitor. I think that the second I replace the oscillator coil it will work perfectly. Please correct me if I'm wrong.
:::::::::: The oscillator coil has two sections on it. One is the Litz wire and the other is the enameled wire.
:::::::::: I think that what you want me to do at the junction of c1 and R9 is to inject an oscillation to see if I can then tune the radio normally with its tuning capacitor.
::::::::::
::::::::::Thanks,
::::::::::
::::::::::Dave
:::::::::::
:::::::::::
:::::::::::
:::::::::::
:::::::::::After reviewing your last postings info:
:::::::::::My fustus “querstion” was if the radio operated in some degree of receiving stations ? via a tunable superheterodyne action / mode prior to the mass recapping of the unit ?
:::::::::::
:::::::::::
:::::::::::
:::::::::::Can we assume that C9..100 mmfd was ok and not even messed with ?
:::::::::::Is cathode resistor R2 wired up ok and at its ~350 ohm value ?
:::::::::::As well as the grid resistor of R1 ….50k wired properly and at its value ?
:::::::::::The last item which I am sure that you did get involved with was the cathode bypass Condenser C7….05 ufd and it is OK and was reinstalled to the correct terminals…right…as that is also as critical as the 3 companion items.
:::::::::::
:::::::::::
:::::::::::
:::::::::::Looks as if the oscillator coil is on the larger ½ to ¾ in coil form and and a Litz wound unit in a tight layer…rather than the old style of enameled wire wound the full length of a long coil form. Plus, you seem to attest of its wirings continuity integrity as well as the adjunct tuning cap and its trimmer caps not being shorted out or dragging plates. Plus the additional reverting of one of the windings for a proper feed back phase check.
:::::::::::Also with your BEE und KAY, you should be able to couple its input into the first grid of the mixer and at the proper injection of CW RF level, be able to swing its dial thru the 1005-2195 khc range and tune thru your stronger receptive stations in the area, with the two “TRF” stations being the powerhouses, BUT with the necessity of having to manually tune the tuning condenser in order to optimize the RF section being in resonance with them, when trying for weaker stations in bringing up received reception level..
:::::::::::
:::::::::::
:::::::::::
:::::::::::To further ease your mind about the radios oscillator sections L-C combinations , you could go to the juncture of C9 and R1 and couple in CW RF via a series / isolative ~100 pf cap and go to the same junction and tack on an anode of a 1N34 / 60 / 64 / 270 GERMANIUM diode and at its cathodes end , take a .001 cap for bypassing to ground and then meter the cathodes output via a VTVM.
:::::::::::
:::::::::::
:::::::::::(N0…1N 914’s/4148’s/1N400oseries for this application)(Radio Shack stocks them in case you don’t have one from an oooold generation AM transistor radio chassis or from the building of a crystal set.)
:::::::::::
:::::::::::
:::::::::::
:::::::::::Then if you will power up the BEE und KAY and place in its CW mode and set the Emerson…(No power required....as this testing will be passive)…to the 1/3 lower end of the dial 700 kc ish (tuning cap ~ ¾ meshed)
:::::::::::Then you tune the B & K in the ~1000-1400 range and see if the co-joined parasitic tuned oscillators circuit doesn’t give you a rising / declining reading as resonance was scanned across.
:::::::::::Then, hop the radios tuning up to the higher third of the band (tuning cap ~ 1/4 meshed) and test for a like reading of a viable resonant circuit pair working at that
:::::::::::frequency also.
:::::::::::Thereby you have merely temp- rigged up a “po boys” grid dipper to interpret the presence of a functioning / resonating effect by the osc sections variable L-C pair and it having some degree of “Q”.
:::::::::::
:::::::::::
:::::::::::The other alternative being that recurrent sweep Eico 460 Scope / Kluge of yours, so I think that with the former detected and metered RF , you would be much better off.
:::::::::::
:::::::::::
:::::::::::
:::::::::::Addenda:
:::::::::::Noticed your new readings just at this posting time, and the bucolic local osc grid voltages reading. And have you confirmed that there is even any level oscillation by the taking of a portable xstr radios ferri-loop and placing it atop the osc coil winding and tune it off station just onto the very edge / sideband of a weaker ~1400-1740 kc AM station and then run the operating radio's tuning condenser across the bottom half of the AM band to see if even a weak heterodyning / birdie is heard on the xstr radio.
:::::::::::
:::::::::::Standing by for feed back
:::::::::::
:::::::::::
:::::::::::73's de Edd
:::::::::::
:::::::::::
:::::::::::
:::::::::::
:::::::::::
:::::::::::
:::::::::::
:::::::::::
:::::::::::
:::::::::::
::::::::::::Marv and all,
::::::::::::
:::::::::::: Here are the voltage readings on the 6A7 tube.
::::::::::::
::::::::::::Pins 1 & 7: 6.8 volts AC (Filament)
::::::::::::Pin 2: 107.5 v DC (Plate)
::::::::::::Pin 3: 43.5 volts DC (G3 and G5)
::::::::::::Pin 4: 106.7 volts (G2)
::::::::::::Pin 5: 2.2 V DC (G1)
::::::::::::Pin 6: 2.647 volts DC (Cathode)
::::::::::::Cap: -.361 v DC (G4)
::::::::::::
::::::::::::These seem like pretty healthy voltages to me. I don't see anything wrong there. The IF transformer is connecting B+ to the plate and the Oscillator coil is connecting B+ to to pin 4. So neither coil is open.
::::::::::::
::::::::::::I did notice that C17 was missing. I put it back and it might have made an improvement but not with the oscillator.
::::::::::::
::::::::::::Please if anyone has anymore ideas before I "attack" (very closely examine) the oscillator coil, please help.
::::::::::::
::::::::::::Thanks,
::::::::::::
::::::::::::Dave
::::::::::::
:::::::::::::Marv,
::::::::::::: My RF signal generator modulates a 400 Hz tone on the 456 Kc carrier frequency when it's set to 456 Kc. The part of the radio that the signal generator is connected to is tune to exactly tuned to 456 Kc. It can receive 456 Kc and only 456 Kc. That "station" is received and I can blast the 400 Hz tone through the speaker of the radio. If I change the RF signal generator to another frequency, then no 400 Hz tone is heard. It is as perfectly aligned as I can get it. It may not have the best adjacent channel rejection but the signal is the strongest when the signal generator is set to 456 Kc.
::::::::::::: The front part of the radio is what I'm having trouble with, and NOT the 456 Kc area. The radio is not converting (moving) the received frequency to 456 Kc. I can hear 570 Kc near the low end of the band and 620 Kc near the high end of the band (I live right near the brodcast antennas for these stations). That's all it does. It absolutely refuses to oscillate under any circumstances. I have checked about all I can check. All is working and not working at the same time.
::::::::::::: The trimmers you are talking about are the oscillator trimmers that can only do anything, are only active, if the oscillator is working. I can put them in any position and they do nothing. They aren't shorted. They are perfectly good but not active because the oscillator is dead.
::::::::::::: C-18 is brand new. It doesn't have any problems. One end is connected to the chassis and the other end is connected to a resistor. R3. I'll double check that it's also connected to the dead oscillator coil. It's not open. It just refuses to oscillate. All 11 paper and 2 electrolytic capacitors have been replaced. The positives of the electrolytic capacitors connect to the same place and the negatives connect to two different places.
::::::::::::: I am getting close to removing the oscillator coil and replacing it or rewinding this one. If only I had the specs for this one. The part number on it is: 2DT200. Maybe someone has an Emerson specs book.
:::::::::::::
:::::::::::::Thanks,
:::::::::::::
:::::::::::::Dave
:::::::::::::
::::::::::::::Dave,
::::::::::::::The oscillator has 2 trimmers in BC mode. One on the tuning cap (C-3) and the other at the rear (C-5), either of which could hamper operation if misadjusted. The one at C-3 is common to both SW and BC. Check C-18. Also, when you tested the IF, (456kHz) were you using signal levels low to moderate or high enough to blast through at any freq?
::::::::::::::
::::::::::::::marv
::::::::::::::
:::::::::::::::Marv,
::::::::::::::: The resistors are the correct value. I checked them. I never replaced them. I also knew that the long black capacitor looking devices were also resistors. They are all correct. The capacitors are in the correct places. Nothing has been changed.
::::::::::::::: I'll check the voltage and double check for "birdies". I think I did hear them. My huge isolation transformer is getting a lot of use on this restoration.
:::::::::::::::
:::::::::::::::Thanks,
:::::::::::::::
:::::::::::::::Dave
:::::::::::::::
::::::::::::::::Dave,
::::::::::::::::In reading your 2 posts, I assume the set never worked and you re-capped and replaced bad resistors first. In this case, did you replace the parts just as they were originally installed, but did you also verify their placement via the schematic?
::::::::::::::::
::::::::::::::::marv
::::::::::::::::
:::::::::::::::::Radiodoc,
::::::::::::::::: I just tried that and it makes absolutely no difference whatsoever.
::::::::::::::::: What do I look at next?
:::::::::::::::::
:::::::::::::::::Thanks,
:::::::::::::::::
::::::::::::::::::Dave,
::::::::::::::::::
::::::::::::::::::The 98 volts is probably ok. If all else failed and as a shot in the dark, I would reverse the coil leads on the non-tuned winding between B+ and the oscillator "plate" and see what happens.
::::::::::::::::::
::::::::::::::::::Radiodoc
::::::::::::::::::***************
::::::::::::::::::
:::::::::::::::::::Radiodoc,
::::::::::::::::::: I took out the oscillator coil and checked every connection and all are good (Perfect), no opens. I checked and cleaned the band switch several times. I replaced C9 several times. When I connect 456 Kc to it from my RF signal generator, it receives that tone perfectly. It blasts!! But it wont take what's presented to it from the antenna terminals and convert that to 456 Kc. It absolutely refuses to do that under any circumstances.
::::::::::::::::::: I checked all the connections and they are perfectly perfectly perfect. The resistors are all the correct values. The solder connections have been re-done and they are nice and shiny.
::::::::::::::::::: I tried 3 different 6A7 tubes and none of them make any difference.
::::::::::::::::::: I checked to make sure that the tuning capacitor or trimmer have any shorts on the oscillator side and there are no shorts. When the set is on and I try to adjust the oscillator screw or short the rotor with the stator on the oscillator side it makes no difference at all. All it's doing is "TRFing". The person who owns this radio MUST have the radio working immediately. I must continue working on it until it works. What do I do next? How do I convert it to a TRF receiver?
:::::::::::::::::::
:::::::::::::::::::Thanks,
:::::::::::::::::::
:::::::::::::::::::Dave
::::::::::::::::::::Radiodoc,
:::::::::::::::::::: B+ is 98 volts. Is that low? Shouldn't it be a little higher? I can't see any way to raise it. Filament voltage on the 6A7 is 5.3 volts.
::::::::::::::::::::
::::::::::::::::::::Thanks,
::::::::::::::::::::
::::::::::::::::::::Dave
:::::::::::::::::::::Radiodoc,
::::::::::::::::::::: C9 is a 100 pf capacitor. I replaced it and it made absolutely no difference.
:::::::::::::::::::::
:::::::::::::::::::::Dave
::::::::::::::::::::::Dave,
::::::::::::::::::::::
::::::::::::::::::::::If all fails, walk away for a while and then come back and check carefully all the wiring around the osc circuit for correctness and good solder joints. Did you check C9 (probably a mica)or replace it. If not may try substituting another. Voltage checks on the stage may give a clue if any are off very much.
::::::::::::::::::::::
::::::::::::::::::::::Radiodoc
::::::::::::::::::::::***********
::::::::::::::::::::::
::::::::::::::::::::::
:::::::::::::::::::::::Hello All,
::::::::::::::::::::::: I have checked everything and the oscillator absolutely refuses to work. All paper and filter capacitors have been replaced. No part of the oscillator coil is open. The resistors are good. I tried a few 6A7s and it still wont work. What to I look at next?
::::::::::::::::::::::: This is an AC/DC set. There's not that much there.
:::::::::::::::::::::::
:::::::::::::::::::::::Thanks,
:::::::::::::::::::::::
:::::::::::::::::::::::Dave
I replaced all the resistors and I still have a very dead oscillator.
Dave
:Dave, You didn't leave any of those old resistors in place? My next try...replace them all regardless of the readings.
:Bill VA
:
::Bill,
:: C8 is brand new. It is a bypass capacitor. The old waxy one was removed from the radio about a week ago. The circuit updates don't seem to have anything to do with the oscillator. The 456 Kc part of the radio works fine.
:: When I attempted to look at C8, R9 (500K), in another part of the radio, fell apart. Also one of the leads fell off of a flexible resistor R2. So I had to replace them. I re-soldered the wire C8 wire to the 6A7 pin and it made absolutely no difference. The oscillator is still dead.
::
:: I do notice now that when the set is on a while, the B+ voltage goes down to 85 volts. These are brand new filter capacitors. So that cannot be the problem. I'll just have to replace every resistor, including the flexible ones. Those crimps onto the carbon must all be failing. I have tons of NOS old style resistors.
::The Oscillator is still Dead Dead Dead.
:: I'll replace the resistors and let everyone know if the oscillator starts to work. It will probably never work. I'll also try 7 or 8 more 6A7s.
:: What should I look at next?
::
::Thanks,
::
::Dave
:::Dave, I'm too slow (both ways) to keep up with this thread. But I got to wade in. C-8 is one to recheck, off the 6A7 screen. Also, just curious, did you need to make the changes to R-9, 11, & 12, and C-13 & 14 based on your serial number?
:::
:::Bill VA
:::
:::
::::Radiodoc,
:::: I just looked through the archives and found that if the voltage is positive it means that the oscillator is not operating. This is what I have been trying to tell you. The oscillator is dead. Ok, good, now we have absolute proof that the oscillator is dead. Now what do I look for? There could still be something not working. The oscillator coil? There is continuity but I don't know what it's value is in micro-henries. All I know is that it's a transformer. It has two primaries for the two bands, and one secondary. The part number on the oscillator coil 2DT200 matches the number in the service data. So it is original.
:::: I'll keep checking the archives to see what others have done in this situation. I think that this may be a common problem. If you know what to check please let me know.
::::
::::Thanks,
::::
::::Dave
:::::
:::::Radiodoc,
::::: Yes, it is positive. Pin 5 is 2.4 volts and pin 6 is 2.8 volts now. The only pins that are negative are the filament pins which are -23 volts DC with respect to the chassis. But they are 6.8 volts AC when I measure across the filament.
::::: Is there something else wrong elsewhere in the set that's preventing the oscillator from working?
:::::
:::::Thanks,
:::::
:::::Dave
:::::
::::::Radiodoc,
:::::: It was 2.2 volts and it wasn't minus. What would be wrong if it's positive?
:::::: I'm going to double check that voltage.
::::::
::::::Thanks,
::::::
::::::Dave
:::::::Dave,
:::::::
:::::::With the radio off did you try measuring between adjacent pins (with tube removed) to see if possibly there is an arc over between pins. You mentioned there was 2 volts on the oscillator grid. There should be a negative voltage on the oscillator grid unless you forgot to type a minus sign in front of the voltage reading you posted.
:::::::
:::::::Radiodoc
:::::::************
:::::::
::::::::Marv,
:::::::: The connections and the voltages are quite good. But it still wont oscillate. It works and absolutely refuses to work all at the same time.
::::::::
::::::::Thanks,
::::::::
::::::::Dave
:::::::::Marv,
::::::::: Yes they are. I measure the pin and the contact and I get the same reading from both. But I'll double check.
:::::::::
:::::::::Thanks,
:::::::::
:::::::::Dave
::::::::::Dave,
::::::::::You have eliminated almost everything. There is one remaining item though. Are you sure the socket/tube pin connections are firm?
::::::::::
::::::::::marv
::::::::::
:::::::::::Edd,
::::::::::: This oscillator is dead, dead, dead. A transistor radio will pick up nothing from it. Also, the radio works exactly the same way whether the oscillator coil is connected to the oscillator side of the tuning capacitor or not. No difference. It absolutely refuses to oscillate even though all is connected perfectly. All components are good too (except for I believe, the oscillator coil). I have more than qadruple checked the 30K, 50K, and 300 whatever ohm resistors. They are hooked up correctly. Also, the another 100pf capacitor was tried and it makes no difference. It's still dead dead dead.
::::::::::: I don't quite understand what you want me to do with the B & K. But I was able to use the B & K to "tune" the radio in the CW position. The rest of the radio receives the 460 Kc perfectly. So it's ready for the oscillator/mixer circuit to work. I am getting ready to replace the oscillator coil. I think I can take one from another AC/DC set just to try it out. Can I do that? I see the that there is a B+ side (output) and the other side that connects to the oscillator side of the tuning capacitor. I think that the second I replace the oscillator coil it will work perfectly. Please correct me if I'm wrong.
::::::::::: The oscillator coil has two sections on it. One is the Litz wire and the other is the enameled wire.
::::::::::: I think that what you want me to do at the junction of c1 and R9 is to inject an oscillation to see if I can then tune the radio normally with its tuning capacitor.
:::::::::::
:::::::::::Thanks,
:::::::::::
:::::::::::Dave
::::::::::::
::::::::::::
::::::::::::
::::::::::::
::::::::::::After reviewing your last postings info:
::::::::::::My fustus “querstion” was if the radio operated in some degree of receiving stations ? via a tunable superheterodyne action / mode prior to the mass recapping of the unit ?
::::::::::::
::::::::::::
::::::::::::
::::::::::::Can we assume that C9..100 mmfd was ok and not even messed with ?
::::::::::::Is cathode resistor R2 wired up ok and at its ~350 ohm value ?
::::::::::::As well as the grid resistor of R1 ….50k wired properly and at its value ?
::::::::::::The last item which I am sure that you did get involved with was the cathode bypass Condenser C7….05 ufd and it is OK and was reinstalled to the correct terminals…right…as that is also as critical as the 3 companion items.
::::::::::::
::::::::::::
::::::::::::
::::::::::::Looks as if the oscillator coil is on the larger ½ to ¾ in coil form and and a Litz wound unit in a tight layer…rather than the old style of enameled wire wound the full length of a long coil form. Plus, you seem to attest of its wirings continuity integrity as well as the adjunct tuning cap and its trimmer caps not being shorted out or dragging plates. Plus the additional reverting of one of the windings for a proper feed back phase check.
::::::::::::Also with your BEE und KAY, you should be able to couple its input into the first grid of the mixer and at the proper injection of CW RF level, be able to swing its dial thru the 1005-2195 khc range and tune thru your stronger receptive stations in the area, with the two “TRF” stations being the powerhouses, BUT with the necessity of having to manually tune the tuning condenser in order to optimize the RF section being in resonance with them, when trying for weaker stations in bringing up received reception level..
::::::::::::
::::::::::::
::::::::::::
::::::::::::To further ease your mind about the radios oscillator sections L-C combinations , you could go to the juncture of C9 and R1 and couple in CW RF via a series / isolative ~100 pf cap and go to the same junction and tack on an anode of a 1N34 / 60 / 64 / 270 GERMANIUM diode and at its cathodes end , take a .001 cap for bypassing to ground and then meter the cathodes output via a VTVM.
::::::::::::
::::::::::::
::::::::::::(N0…1N 914’s/4148’s/1N400oseries for this application)(Radio Shack stocks them in case you don’t have one from an oooold generation AM transistor radio chassis or from the building of a crystal set.)
::::::::::::
::::::::::::
::::::::::::
::::::::::::Then if you will power up the BEE und KAY and place in its CW mode and set the Emerson…(No power required....as this testing will be passive)…to the 1/3 lower end of the dial 700 kc ish (tuning cap ~ ¾ meshed)
::::::::::::Then you tune the B & K in the ~1000-1400 range and see if the co-joined parasitic tuned oscillators circuit doesn’t give you a rising / declining reading as resonance was scanned across.
::::::::::::Then, hop the radios tuning up to the higher third of the band (tuning cap ~ 1/4 meshed) and test for a like reading of a viable resonant circuit pair working at that
::::::::::::frequency also.
::::::::::::Thereby you have merely temp- rigged up a “po boys” grid dipper to interpret the presence of a functioning / resonating effect by the osc sections variable L-C pair and it having some degree of “Q”.
::::::::::::
::::::::::::
::::::::::::The other alternative being that recurrent sweep Eico 460 Scope / Kluge of yours, so I think that with the former detected and metered RF , you would be much better off.
::::::::::::
::::::::::::
::::::::::::
::::::::::::Addenda:
::::::::::::Noticed your new readings just at this posting time, and the bucolic local osc grid voltages reading. And have you confirmed that there is even any level oscillation by the taking of a portable xstr radios ferri-loop and placing it atop the osc coil winding and tune it off station just onto the very edge / sideband of a weaker ~1400-1740 kc AM station and then run the operating radio's tuning condenser across the bottom half of the AM band to see if even a weak heterodyning / birdie is heard on the xstr radio.
::::::::::::
::::::::::::Standing by for feed back
::::::::::::
::::::::::::
::::::::::::73's de Edd
::::::::::::
::::::::::::
::::::::::::
::::::::::::
::::::::::::
::::::::::::
::::::::::::
::::::::::::
::::::::::::
::::::::::::
:::::::::::::Marv and all,
:::::::::::::
::::::::::::: Here are the voltage readings on the 6A7 tube.
:::::::::::::
:::::::::::::Pins 1 & 7: 6.8 volts AC (Filament)
:::::::::::::Pin 2: 107.5 v DC (Plate)
:::::::::::::Pin 3: 43.5 volts DC (G3 and G5)
:::::::::::::Pin 4: 106.7 volts (G2)
:::::::::::::Pin 5: 2.2 V DC (G1)
:::::::::::::Pin 6: 2.647 volts DC (Cathode)
:::::::::::::Cap: -.361 v DC (G4)
:::::::::::::
:::::::::::::These seem like pretty healthy voltages to me. I don't see anything wrong there. The IF transformer is connecting B+ to the plate and the Oscillator coil is connecting B+ to to pin 4. So neither coil is open.
:::::::::::::
:::::::::::::I did notice that C17 was missing. I put it back and it might have made an improvement but not with the oscillator.
:::::::::::::
:::::::::::::Please if anyone has anymore ideas before I "attack" (very closely examine) the oscillator coil, please help.
:::::::::::::
:::::::::::::Thanks,
:::::::::::::
:::::::::::::Dave
:::::::::::::
::::::::::::::Marv,
:::::::::::::: My RF signal generator modulates a 400 Hz tone on the 456 Kc carrier frequency when it's set to 456 Kc. The part of the radio that the signal generator is connected to is tune to exactly tuned to 456 Kc. It can receive 456 Kc and only 456 Kc. That "station" is received and I can blast the 400 Hz tone through the speaker of the radio. If I change the RF signal generator to another frequency, then no 400 Hz tone is heard. It is as perfectly aligned as I can get it. It may not have the best adjacent channel rejection but the signal is the strongest when the signal generator is set to 456 Kc.
:::::::::::::: The front part of the radio is what I'm having trouble with, and NOT the 456 Kc area. The radio is not converting (moving) the received frequency to 456 Kc. I can hear 570 Kc near the low end of the band and 620 Kc near the high end of the band (I live right near the brodcast antennas for these stations). That's all it does. It absolutely refuses to oscillate under any circumstances. I have checked about all I can check. All is working and not working at the same time.
:::::::::::::: The trimmers you are talking about are the oscillator trimmers that can only do anything, are only active, if the oscillator is working. I can put them in any position and they do nothing. They aren't shorted. They are perfectly good but not active because the oscillator is dead.
:::::::::::::: C-18 is brand new. It doesn't have any problems. One end is connected to the chassis and the other end is connected to a resistor. R3. I'll double check that it's also connected to the dead oscillator coil. It's not open. It just refuses to oscillate. All 11 paper and 2 electrolytic capacitors have been replaced. The positives of the electrolytic capacitors connect to the same place and the negatives connect to two different places.
:::::::::::::: I am getting close to removing the oscillator coil and replacing it or rewinding this one. If only I had the specs for this one. The part number on it is: 2DT200. Maybe someone has an Emerson specs book.
::::::::::::::
::::::::::::::Thanks,
::::::::::::::
::::::::::::::Dave
::::::::::::::
:::::::::::::::Dave,
:::::::::::::::The oscillator has 2 trimmers in BC mode. One on the tuning cap (C-3) and the other at the rear (C-5), either of which could hamper operation if misadjusted. The one at C-3 is common to both SW and BC. Check C-18. Also, when you tested the IF, (456kHz) were you using signal levels low to moderate or high enough to blast through at any freq?
:::::::::::::::
:::::::::::::::marv
:::::::::::::::
::::::::::::::::Marv,
:::::::::::::::: The resistors are the correct value. I checked them. I never replaced them. I also knew that the long black capacitor looking devices were also resistors. They are all correct. The capacitors are in the correct places. Nothing has been changed.
:::::::::::::::: I'll check the voltage and double check for "birdies". I think I did hear them. My huge isolation transformer is getting a lot of use on this restoration.
::::::::::::::::
::::::::::::::::Thanks,
::::::::::::::::
::::::::::::::::Dave
::::::::::::::::
:::::::::::::::::Dave,
:::::::::::::::::In reading your 2 posts, I assume the set never worked and you re-capped and replaced bad resistors first. In this case, did you replace the parts just as they were originally installed, but did you also verify their placement via the schematic?
:::::::::::::::::
:::::::::::::::::marv
:::::::::::::::::
::::::::::::::::::Radiodoc,
:::::::::::::::::: I just tried that and it makes absolutely no difference whatsoever.
:::::::::::::::::: What do I look at next?
::::::::::::::::::
::::::::::::::::::Thanks,
::::::::::::::::::
:::::::::::::::::::Dave,
:::::::::::::::::::
:::::::::::::::::::The 98 volts is probably ok. If all else failed and as a shot in the dark, I would reverse the coil leads on the non-tuned winding between B+ and the oscillator "plate" and see what happens.
:::::::::::::::::::
:::::::::::::::::::Radiodoc
:::::::::::::::::::***************
:::::::::::::::::::
::::::::::::::::::::Radiodoc,
:::::::::::::::::::: I took out the oscillator coil and checked every connection and all are good (Perfect), no opens. I checked and cleaned the band switch several times. I replaced C9 several times. When I connect 456 Kc to it from my RF signal generator, it receives that tone perfectly. It blasts!! But it wont take what's presented to it from the antenna terminals and convert that to 456 Kc. It absolutely refuses to do that under any circumstances.
:::::::::::::::::::: I checked all the connections and they are perfectly perfectly perfect. The resistors are all the correct values. The solder connections have been re-done and they are nice and shiny.
:::::::::::::::::::: I tried 3 different 6A7 tubes and none of them make any difference.
:::::::::::::::::::: I checked to make sure that the tuning capacitor or trimmer have any shorts on the oscillator side and there are no shorts. When the set is on and I try to adjust the oscillator screw or short the rotor with the stator on the oscillator side it makes no difference at all. All it's doing is "TRFing". The person who owns this radio MUST have the radio working immediately. I must continue working on it until it works. What do I do next? How do I convert it to a TRF receiver?
::::::::::::::::::::
::::::::::::::::::::Thanks,
::::::::::::::::::::
::::::::::::::::::::Dave
:::::::::::::::::::::Radiodoc,
::::::::::::::::::::: B+ is 98 volts. Is that low? Shouldn't it be a little higher? I can't see any way to raise it. Filament voltage on the 6A7 is 5.3 volts.
:::::::::::::::::::::
:::::::::::::::::::::Thanks,
:::::::::::::::::::::
:::::::::::::::::::::Dave
::::::::::::::::::::::Radiodoc,
:::::::::::::::::::::: C9 is a 100 pf capacitor. I replaced it and it made absolutely no difference.
::::::::::::::::::::::
::::::::::::::::::::::Dave
:::::::::::::::::::::::Dave,
:::::::::::::::::::::::
:::::::::::::::::::::::If all fails, walk away for a while and then come back and check carefully all the wiring around the osc circuit for correctness and good solder joints. Did you check C9 (probably a mica)or replace it. If not may try substituting another. Voltage checks on the stage may give a clue if any are off very much.
:::::::::::::::::::::::
:::::::::::::::::::::::Radiodoc
:::::::::::::::::::::::***********
:::::::::::::::::::::::
:::::::::::::::::::::::
::::::::::::::::::::::::Hello All,
:::::::::::::::::::::::: I have checked everything and the oscillator absolutely refuses to work. All paper and filter capacitors have been replaced. No part of the oscillator coil is open. The resistors are good. I tried a few 6A7s and it still wont work. What to I look at next?
:::::::::::::::::::::::: This is an AC/DC set. There's not that much there.
::::::::::::::::::::::::
::::::::::::::::::::::::Thanks,
::::::::::::::::::::::::
::::::::::::::::::::::::Dave
Bill VA
Bill VA
:Bill,
:
: I replaced all the resistors and I still have a very dead oscillator.
:
:Dave
::Dave, You didn't leave any of those old resistors in place? My next try...replace them all regardless of the readings.
::Bill VA
::
:::Bill,
::: C8 is brand new. It is a bypass capacitor. The old waxy one was removed from the radio about a week ago. The circuit updates don't seem to have anything to do with the oscillator. The 456 Kc part of the radio works fine.
::: When I attempted to look at C8, R9 (500K), in another part of the radio, fell apart. Also one of the leads fell off of a flexible resistor R2. So I had to replace them. I re-soldered the wire C8 wire to the 6A7 pin and it made absolutely no difference. The oscillator is still dead.
:::
::: I do notice now that when the set is on a while, the B+ voltage goes down to 85 volts. These are brand new filter capacitors. So that cannot be the problem. I'll just have to replace every resistor, including the flexible ones. Those crimps onto the carbon must all be failing. I have tons of NOS old style resistors.
:::The Oscillator is still Dead Dead Dead.
::: I'll replace the resistors and let everyone know if the oscillator starts to work. It will probably never work. I'll also try 7 or 8 more 6A7s.
::: What should I look at next?
:::
:::Thanks,
:::
:::Dave
::::Dave, I'm too slow (both ways) to keep up with this thread. But I got to wade in. C-8 is one to recheck, off the 6A7 screen. Also, just curious, did you need to make the changes to R-9, 11, & 12, and C-13 & 14 based on your serial number?
::::
::::Bill VA
::::
::::
:::::Radiodoc,
::::: I just looked through the archives and found that if the voltage is positive it means that the oscillator is not operating. This is what I have been trying to tell you. The oscillator is dead. Ok, good, now we have absolute proof that the oscillator is dead. Now what do I look for? There could still be something not working. The oscillator coil? There is continuity but I don't know what it's value is in micro-henries. All I know is that it's a transformer. It has two primaries for the two bands, and one secondary. The part number on the oscillator coil 2DT200 matches the number in the service data. So it is original.
::::: I'll keep checking the archives to see what others have done in this situation. I think that this may be a common problem. If you know what to check please let me know.
:::::
:::::Thanks,
:::::
:::::Dave
::::::
::::::Radiodoc,
:::::: Yes, it is positive. Pin 5 is 2.4 volts and pin 6 is 2.8 volts now. The only pins that are negative are the filament pins which are -23 volts DC with respect to the chassis. But they are 6.8 volts AC when I measure across the filament.
:::::: Is there something else wrong elsewhere in the set that's preventing the oscillator from working?
::::::
::::::Thanks,
::::::
::::::Dave
::::::
:::::::Radiodoc,
::::::: It was 2.2 volts and it wasn't minus. What would be wrong if it's positive?
::::::: I'm going to double check that voltage.
:::::::
:::::::Thanks,
:::::::
:::::::Dave
::::::::Dave,
::::::::
::::::::With the radio off did you try measuring between adjacent pins (with tube removed) to see if possibly there is an arc over between pins. You mentioned there was 2 volts on the oscillator grid. There should be a negative voltage on the oscillator grid unless you forgot to type a minus sign in front of the voltage reading you posted.
::::::::
::::::::Radiodoc
::::::::************
::::::::
:::::::::Marv,
::::::::: The connections and the voltages are quite good. But it still wont oscillate. It works and absolutely refuses to work all at the same time.
:::::::::
:::::::::Thanks,
:::::::::
:::::::::Dave
::::::::::Marv,
:::::::::: Yes they are. I measure the pin and the contact and I get the same reading from both. But I'll double check.
::::::::::
::::::::::Thanks,
::::::::::
::::::::::Dave
:::::::::::Dave,
:::::::::::You have eliminated almost everything. There is one remaining item though. Are you sure the socket/tube pin connections are firm?
:::::::::::
:::::::::::marv
:::::::::::
::::::::::::Edd,
:::::::::::: This oscillator is dead, dead, dead. A transistor radio will pick up nothing from it. Also, the radio works exactly the same way whether the oscillator coil is connected to the oscillator side of the tuning capacitor or not. No difference. It absolutely refuses to oscillate even though all is connected perfectly. All components are good too (except for I believe, the oscillator coil). I have more than qadruple checked the 30K, 50K, and 300 whatever ohm resistors. They are hooked up correctly. Also, the another 100pf capacitor was tried and it makes no difference. It's still dead dead dead.
:::::::::::: I don't quite understand what you want me to do with the B & K. But I was able to use the B & K to "tune" the radio in the CW position. The rest of the radio receives the 460 Kc perfectly. So it's ready for the oscillator/mixer circuit to work. I am getting ready to replace the oscillator coil. I think I can take one from another AC/DC set just to try it out. Can I do that? I see the that there is a B+ side (output) and the other side that connects to the oscillator side of the tuning capacitor. I think that the second I replace the oscillator coil it will work perfectly. Please correct me if I'm wrong.
:::::::::::: The oscillator coil has two sections on it. One is the Litz wire and the other is the enameled wire.
:::::::::::: I think that what you want me to do at the junction of c1 and R9 is to inject an oscillation to see if I can then tune the radio normally with its tuning capacitor.
::::::::::::
::::::::::::Thanks,
::::::::::::
::::::::::::Dave
:::::::::::::
:::::::::::::
:::::::::::::
:::::::::::::
:::::::::::::After reviewing your last postings info:
:::::::::::::My fustus “querstion” was if the radio operated in some degree of receiving stations ? via a tunable superheterodyne action / mode prior to the mass recapping of the unit ?
:::::::::::::
:::::::::::::
:::::::::::::
:::::::::::::Can we assume that C9..100 mmfd was ok and not even messed with ?
:::::::::::::Is cathode resistor R2 wired up ok and at its ~350 ohm value ?
:::::::::::::As well as the grid resistor of R1 ….50k wired properly and at its value ?
:::::::::::::The last item which I am sure that you did get involved with was the cathode bypass Condenser C7….05 ufd and it is OK and was reinstalled to the correct terminals…right…as that is also as critical as the 3 companion items.
:::::::::::::
:::::::::::::
:::::::::::::
:::::::::::::Looks as if the oscillator coil is on the larger ½ to ¾ in coil form and and a Litz wound unit in a tight layer…rather than the old style of enameled wire wound the full length of a long coil form. Plus, you seem to attest of its wirings continuity integrity as well as the adjunct tuning cap and its trimmer caps not being shorted out or dragging plates. Plus the additional reverting of one of the windings for a proper feed back phase check.
:::::::::::::Also with your BEE und KAY, you should be able to couple its input into the first grid of the mixer and at the proper injection of CW RF level, be able to swing its dial thru the 1005-2195 khc range and tune thru your stronger receptive stations in the area, with the two “TRF” stations being the powerhouses, BUT with the necessity of having to manually tune the tuning condenser in order to optimize the RF section being in resonance with them, when trying for weaker stations in bringing up received reception level..
:::::::::::::
:::::::::::::
:::::::::::::
:::::::::::::To further ease your mind about the radios oscillator sections L-C combinations , you could go to the juncture of C9 and R1 and couple in CW RF via a series / isolative ~100 pf cap and go to the same junction and tack on an anode of a 1N34 / 60 / 64 / 270 GERMANIUM diode and at its cathodes end , take a .001 cap for bypassing to ground and then meter the cathodes output via a VTVM.
:::::::::::::
:::::::::::::
:::::::::::::(N0…1N 914’s/4148’s/1N400oseries for this application)(Radio Shack stocks them in case you don’t have one from an oooold generation AM transistor radio chassis or from the building of a crystal set.)
:::::::::::::
:::::::::::::
:::::::::::::
:::::::::::::Then if you will power up the BEE und KAY and place in its CW mode and set the Emerson…(No power required....as this testing will be passive)…to the 1/3 lower end of the dial 700 kc ish (tuning cap ~ ¾ meshed)
:::::::::::::Then you tune the B & K in the ~1000-1400 range and see if the co-joined parasitic tuned oscillators circuit doesn’t give you a rising / declining reading as resonance was scanned across.
:::::::::::::Then, hop the radios tuning up to the higher third of the band (tuning cap ~ 1/4 meshed) and test for a like reading of a viable resonant circuit pair working at that
:::::::::::::frequency also.
:::::::::::::Thereby you have merely temp- rigged up a “po boys” grid dipper to interpret the presence of a functioning / resonating effect by the osc sections variable L-C pair and it having some degree of “Q”.
:::::::::::::
:::::::::::::
:::::::::::::The other alternative being that recurrent sweep Eico 460 Scope / Kluge of yours, so I think that with the former detected and metered RF , you would be much better off.
:::::::::::::
:::::::::::::
:::::::::::::
:::::::::::::Addenda:
:::::::::::::Noticed your new readings just at this posting time, and the bucolic local osc grid voltages reading. And have you confirmed that there is even any level oscillation by the taking of a portable xstr radios ferri-loop and placing it atop the osc coil winding and tune it off station just onto the very edge / sideband of a weaker ~1400-1740 kc AM station and then run the operating radio's tuning condenser across the bottom half of the AM band to see if even a weak heterodyning / birdie is heard on the xstr radio.
:::::::::::::
:::::::::::::Standing by for feed back
:::::::::::::
:::::::::::::
:::::::::::::73's de Edd
:::::::::::::
:::::::::::::
:::::::::::::
:::::::::::::
:::::::::::::
:::::::::::::
:::::::::::::
:::::::::::::
:::::::::::::
:::::::::::::
::::::::::::::Marv and all,
::::::::::::::
:::::::::::::: Here are the voltage readings on the 6A7 tube.
::::::::::::::
::::::::::::::Pins 1 & 7: 6.8 volts AC (Filament)
::::::::::::::Pin 2: 107.5 v DC (Plate)
::::::::::::::Pin 3: 43.5 volts DC (G3 and G5)
::::::::::::::Pin 4: 106.7 volts (G2)
::::::::::::::Pin 5: 2.2 V DC (G1)
::::::::::::::Pin 6: 2.647 volts DC (Cathode)
::::::::::::::Cap: -.361 v DC (G4)
::::::::::::::
::::::::::::::These seem like pretty healthy voltages to me. I don't see anything wrong there. The IF transformer is connecting B+ to the plate and the Oscillator coil is connecting B+ to to pin 4. So neither coil is open.
::::::::::::::
::::::::::::::I did notice that C17 was missing. I put it back and it might have made an improvement but not with the oscillator.
::::::::::::::
::::::::::::::Please if anyone has anymore ideas before I "attack" (very closely examine) the oscillator coil, please help.
::::::::::::::
::::::::::::::Thanks,
::::::::::::::
::::::::::::::Dave
::::::::::::::
:::::::::::::::Marv,
::::::::::::::: My RF signal generator modulates a 400 Hz tone on the 456 Kc carrier frequency when it's set to 456 Kc. The part of the radio that the signal generator is connected to is tune to exactly tuned to 456 Kc. It can receive 456 Kc and only 456 Kc. That "station" is received and I can blast the 400 Hz tone through the speaker of the radio. If I change the RF signal generator to another frequency, then no 400 Hz tone is heard. It is as perfectly aligned as I can get it. It may not have the best adjacent channel rejection but the signal is the strongest when the signal generator is set to 456 Kc.
::::::::::::::: The front part of the radio is what I'm having trouble with, and NOT the 456 Kc area. The radio is not converting (moving) the received frequency to 456 Kc. I can hear 570 Kc near the low end of the band and 620 Kc near the high end of the band (I live right near the brodcast antennas for these stations). That's all it does. It absolutely refuses to oscillate under any circumstances. I have checked about all I can check. All is working and not working at the same time.
::::::::::::::: The trimmers you are talking about are the oscillator trimmers that can only do anything, are only active, if the oscillator is working. I can put them in any position and they do nothing. They aren't shorted. They are perfectly good but not active because the oscillator is dead.
::::::::::::::: C-18 is brand new. It doesn't have any problems. One end is connected to the chassis and the other end is connected to a resistor. R3. I'll double check that it's also connected to the dead oscillator coil. It's not open. It just refuses to oscillate. All 11 paper and 2 electrolytic capacitors have been replaced. The positives of the electrolytic capacitors connect to the same place and the negatives connect to two different places.
::::::::::::::: I am getting close to removing the oscillator coil and replacing it or rewinding this one. If only I had the specs for this one. The part number on it is: 2DT200. Maybe someone has an Emerson specs book.
:::::::::::::::
:::::::::::::::Thanks,
:::::::::::::::
:::::::::::::::Dave
:::::::::::::::
::::::::::::::::Dave,
::::::::::::::::The oscillator has 2 trimmers in BC mode. One on the tuning cap (C-3) and the other at the rear (C-5), either of which could hamper operation if misadjusted. The one at C-3 is common to both SW and BC. Check C-18. Also, when you tested the IF, (456kHz) were you using signal levels low to moderate or high enough to blast through at any freq?
::::::::::::::::
::::::::::::::::marv
::::::::::::::::
:::::::::::::::::Marv,
::::::::::::::::: The resistors are the correct value. I checked them. I never replaced them. I also knew that the long black capacitor looking devices were also resistors. They are all correct. The capacitors are in the correct places. Nothing has been changed.
::::::::::::::::: I'll check the voltage and double check for "birdies". I think I did hear them. My huge isolation transformer is getting a lot of use on this restoration.
:::::::::::::::::
:::::::::::::::::Thanks,
:::::::::::::::::
:::::::::::::::::Dave
:::::::::::::::::
::::::::::::::::::Dave,
::::::::::::::::::In reading your 2 posts, I assume the set never worked and you re-capped and replaced bad resistors first. In this case, did you replace the parts just as they were originally installed, but did you also verify their placement via the schematic?
::::::::::::::::::
::::::::::::::::::marv
::::::::::::::::::
:::::::::::::::::::Radiodoc,
::::::::::::::::::: I just tried that and it makes absolutely no difference whatsoever.
::::::::::::::::::: What do I look at next?
:::::::::::::::::::
:::::::::::::::::::Thanks,
:::::::::::::::::::
::::::::::::::::::::Dave,
::::::::::::::::::::
::::::::::::::::::::The 98 volts is probably ok. If all else failed and as a shot in the dark, I would reverse the coil leads on the non-tuned winding between B+ and the oscillator "plate" and see what happens.
::::::::::::::::::::
::::::::::::::::::::Radiodoc
::::::::::::::::::::***************
::::::::::::::::::::
:::::::::::::::::::::Radiodoc,
::::::::::::::::::::: I took out the oscillator coil and checked every connection and all are good (Perfect), no opens. I checked and cleaned the band switch several times. I replaced C9 several times. When I connect 456 Kc to it from my RF signal generator, it receives that tone perfectly. It blasts!! But it wont take what's presented to it from the antenna terminals and convert that to 456 Kc. It absolutely refuses to do that under any circumstances.
::::::::::::::::::::: I checked all the connections and they are perfectly perfectly perfect. The resistors are all the correct values. The solder connections have been re-done and they are nice and shiny.
::::::::::::::::::::: I tried 3 different 6A7 tubes and none of them make any difference.
::::::::::::::::::::: I checked to make sure that the tuning capacitor or trimmer have any shorts on the oscillator side and there are no shorts. When the set is on and I try to adjust the oscillator screw or short the rotor with the stator on the oscillator side it makes no difference at all. All it's doing is "TRFing". The person who owns this radio MUST have the radio working immediately. I must continue working on it until it works. What do I do next? How do I convert it to a TRF receiver?
:::::::::::::::::::::
:::::::::::::::::::::Thanks,
:::::::::::::::::::::
:::::::::::::::::::::Dave
::::::::::::::::::::::Radiodoc,
:::::::::::::::::::::: B+ is 98 volts. Is that low? Shouldn't it be a little higher? I can't see any way to raise it. Filament voltage on the 6A7 is 5.3 volts.
::::::::::::::::::::::
::::::::::::::::::::::Thanks,
::::::::::::::::::::::
::::::::::::::::::::::Dave
:::::::::::::::::::::::Radiodoc,
::::::::::::::::::::::: C9 is a 100 pf capacitor. I replaced it and it made absolutely no difference.
:::::::::::::::::::::::
:::::::::::::::::::::::Dave
::::::::::::::::::::::::Dave,
::::::::::::::::::::::::
::::::::::::::::::::::::If all fails, walk away for a while and then come back and check carefully all the wiring around the osc circuit for correctness and good solder joints. Did you check C9 (probably a mica)or replace it. If not may try substituting another. Voltage checks on the stage may give a clue if any are off very much.
::::::::::::::::::::::::
::::::::::::::::::::::::Radiodoc
::::::::::::::::::::::::***********
::::::::::::::::::::::::
::::::::::::::::::::::::
:::::::::::::::::::::::::Hello All,
::::::::::::::::::::::::: I have checked everything and the oscillator absolutely refuses to work. All paper and filter capacitors have been replaced. No part of the oscillator coil is open. The resistors are good. I tried a few 6A7s and it still wont work. What to I look at next?
::::::::::::::::::::::::: This is an AC/DC set. There's not that much there.
:::::::::::::::::::::::::
:::::::::::::::::::::::::Thanks,
:::::::::::::::::::::::::
:::::::::::::::::::::::::Dave
C19 doesn't connect to the chassis. Who said that it does? I don't have 82 volts anymore. It's 115 or 116 and the oscillator is still dead. I have tried various oscillator coils and substituted IF transformers and it's still dead dead dead.
The voltage on pin 5 with the last IF transformer I tried, was 2.8 volts. Pin 6 was 3 volts.
What do I try next? I have replaced and cleaned cleaned cleaned all the switch contacts several times. I have tried 7 6A7s. Replaced all the resistors. I have tried different C9s, and it still absolutely refuses to oscillate. The only thing I can do is use my RF signal generator as the oscillator. Then the voltage on pin 5 goes negative. Nothing else can get it to do that. What's going on? I don't think that the owner of the radio wants to have an RF signal generator attached to it permanently.
THere must be something left to replace. But what?
Thanks,
Dave
:Dave, to me your B+ is low even before it drops to 82V. The schematic indicates voltage readings at 117. I would at least expect B+ on today's line voltage to be higher rather than lower tho 98 sounds ok if steady. I would take the voltage measurements as stated accross the field coil and the choke. C19 does not connect to the chassis. I used to tell my boys when working on dirt bikes or cars, look for something simple causing the problem. I did come home a couple times and parts be laying everywhere...waiting on me. I think you have tried about everything and I know it gets aggravating. But you'll get it and we all will say ahhh.
:Bill VA
:Bill VA
:
:
::Bill,
::
:: I replaced all the resistors and I still have a very dead oscillator.
::
::Dave
:::Dave, You didn't leave any of those old resistors in place? My next try...replace them all regardless of the readings.
:::Bill VA
:::
::::Bill,
:::: C8 is brand new. It is a bypass capacitor. The old waxy one was removed from the radio about a week ago. The circuit updates don't seem to have anything to do with the oscillator. The 456 Kc part of the radio works fine.
:::: When I attempted to look at C8, R9 (500K), in another part of the radio, fell apart. Also one of the leads fell off of a flexible resistor R2. So I had to replace them. I re-soldered the wire C8 wire to the 6A7 pin and it made absolutely no difference. The oscillator is still dead.
::::
:::: I do notice now that when the set is on a while, the B+ voltage goes down to 85 volts. These are brand new filter capacitors. So that cannot be the problem. I'll just have to replace every resistor, including the flexible ones. Those crimps onto the carbon must all be failing. I have tons of NOS old style resistors.
::::The Oscillator is still Dead Dead Dead.
:::: I'll replace the resistors and let everyone know if the oscillator starts to work. It will probably never work. I'll also try 7 or 8 more 6A7s.
:::: What should I look at next?
::::
::::Thanks,
::::
::::Dave
:::::Dave, I'm too slow (both ways) to keep up with this thread. But I got to wade in. C-8 is one to recheck, off the 6A7 screen. Also, just curious, did you need to make the changes to R-9, 11, & 12, and C-13 & 14 based on your serial number?
:::::
:::::Bill VA
:::::
:::::
::::::Radiodoc,
:::::: I just looked through the archives and found that if the voltage is positive it means that the oscillator is not operating. This is what I have been trying to tell you. The oscillator is dead. Ok, good, now we have absolute proof that the oscillator is dead. Now what do I look for? There could still be something not working. The oscillator coil? There is continuity but I don't know what it's value is in micro-henries. All I know is that it's a transformer. It has two primaries for the two bands, and one secondary. The part number on the oscillator coil 2DT200 matches the number in the service data. So it is original.
:::::: I'll keep checking the archives to see what others have done in this situation. I think that this may be a common problem. If you know what to check please let me know.
::::::
::::::Thanks,
::::::
::::::Dave
:::::::
:::::::Radiodoc,
::::::: Yes, it is positive. Pin 5 is 2.4 volts and pin 6 is 2.8 volts now. The only pins that are negative are the filament pins which are -23 volts DC with respect to the chassis. But they are 6.8 volts AC when I measure across the filament.
::::::: Is there something else wrong elsewhere in the set that's preventing the oscillator from working?
:::::::
:::::::Thanks,
:::::::
:::::::Dave
:::::::
::::::::Radiodoc,
:::::::: It was 2.2 volts and it wasn't minus. What would be wrong if it's positive?
:::::::: I'm going to double check that voltage.
::::::::
::::::::Thanks,
::::::::
::::::::Dave
:::::::::Dave,
:::::::::
:::::::::With the radio off did you try measuring between adjacent pins (with tube removed) to see if possibly there is an arc over between pins. You mentioned there was 2 volts on the oscillator grid. There should be a negative voltage on the oscillator grid unless you forgot to type a minus sign in front of the voltage reading you posted.
:::::::::
:::::::::Radiodoc
:::::::::************
:::::::::
::::::::::Marv,
:::::::::: The connections and the voltages are quite good. But it still wont oscillate. It works and absolutely refuses to work all at the same time.
::::::::::
::::::::::Thanks,
::::::::::
::::::::::Dave
:::::::::::Marv,
::::::::::: Yes they are. I measure the pin and the contact and I get the same reading from both. But I'll double check.
:::::::::::
:::::::::::Thanks,
:::::::::::
:::::::::::Dave
::::::::::::Dave,
::::::::::::You have eliminated almost everything. There is one remaining item though. Are you sure the socket/tube pin connections are firm?
::::::::::::
::::::::::::marv
::::::::::::
:::::::::::::Edd,
::::::::::::: This oscillator is dead, dead, dead. A transistor radio will pick up nothing from it. Also, the radio works exactly the same way whether the oscillator coil is connected to the oscillator side of the tuning capacitor or not. No difference. It absolutely refuses to oscillate even though all is connected perfectly. All components are good too (except for I believe, the oscillator coil). I have more than qadruple checked the 30K, 50K, and 300 whatever ohm resistors. They are hooked up correctly. Also, the another 100pf capacitor was tried and it makes no difference. It's still dead dead dead.
::::::::::::: I don't quite understand what you want me to do with the B & K. But I was able to use the B & K to "tune" the radio in the CW position. The rest of the radio receives the 460 Kc perfectly. So it's ready for the oscillator/mixer circuit to work. I am getting ready to replace the oscillator coil. I think I can take one from another AC/DC set just to try it out. Can I do that? I see the that there is a B+ side (output) and the other side that connects to the oscillator side of the tuning capacitor. I think that the second I replace the oscillator coil it will work perfectly. Please correct me if I'm wrong.
::::::::::::: The oscillator coil has two sections on it. One is the Litz wire and the other is the enameled wire.
::::::::::::: I think that what you want me to do at the junction of c1 and R9 is to inject an oscillation to see if I can then tune the radio normally with its tuning capacitor.
:::::::::::::
:::::::::::::Thanks,
:::::::::::::
:::::::::::::Dave
::::::::::::::
::::::::::::::
::::::::::::::
::::::::::::::
::::::::::::::After reviewing your last postings info:
::::::::::::::My fustus “querstion” was if the radio operated in some degree of receiving stations ? via a tunable superheterodyne action / mode prior to the mass recapping of the unit ?
::::::::::::::
::::::::::::::
::::::::::::::
::::::::::::::Can we assume that C9..100 mmfd was ok and not even messed with ?
::::::::::::::Is cathode resistor R2 wired up ok and at its ~350 ohm value ?
::::::::::::::As well as the grid resistor of R1 ….50k wired properly and at its value ?
::::::::::::::The last item which I am sure that you did get involved with was the cathode bypass Condenser C7….05 ufd and it is OK and was reinstalled to the correct terminals…right…as that is also as critical as the 3 companion items.
::::::::::::::
::::::::::::::
::::::::::::::
::::::::::::::Looks as if the oscillator coil is on the larger ½ to ¾ in coil form and and a Litz wound unit in a tight layer…rather than the old style of enameled wire wound the full length of a long coil form. Plus, you seem to attest of its wirings continuity integrity as well as the adjunct tuning cap and its trimmer caps not being shorted out or dragging plates. Plus the additional reverting of one of the windings for a proper feed back phase check.
::::::::::::::Also with your BEE und KAY, you should be able to couple its input into the first grid of the mixer and at the proper injection of CW RF level, be able to swing its dial thru the 1005-2195 khc range and tune thru your stronger receptive stations in the area, with the two “TRF” stations being the powerhouses, BUT with the necessity of having to manually tune the tuning condenser in order to optimize the RF section being in resonance with them, when trying for weaker stations in bringing up received reception level..
::::::::::::::
::::::::::::::
::::::::::::::
::::::::::::::To further ease your mind about the radios oscillator sections L-C combinations , you could go to the juncture of C9 and R1 and couple in CW RF via a series / isolative ~100 pf cap and go to the same junction and tack on an anode of a 1N34 / 60 / 64 / 270 GERMANIUM diode and at its cathodes end , take a .001 cap for bypassing to ground and then meter the cathodes output via a VTVM.
::::::::::::::
::::::::::::::
::::::::::::::(N0…1N 914’s/4148’s/1N400oseries for this application)(Radio Shack stocks them in case you don’t have one from an oooold generation AM transistor radio chassis or from the building of a crystal set.)
::::::::::::::
::::::::::::::
::::::::::::::
::::::::::::::Then if you will power up the BEE und KAY and place in its CW mode and set the Emerson…(No power required....as this testing will be passive)…to the 1/3 lower end of the dial 700 kc ish (tuning cap ~ ¾ meshed)
::::::::::::::Then you tune the B & K in the ~1000-1400 range and see if the co-joined parasitic tuned oscillators circuit doesn’t give you a rising / declining reading as resonance was scanned across.
::::::::::::::Then, hop the radios tuning up to the higher third of the band (tuning cap ~ 1/4 meshed) and test for a like reading of a viable resonant circuit pair working at that
::::::::::::::frequency also.
::::::::::::::Thereby you have merely temp- rigged up a “po boys” grid dipper to interpret the presence of a functioning / resonating effect by the osc sections variable L-C pair and it having some degree of “Q”.
::::::::::::::
::::::::::::::
::::::::::::::The other alternative being that recurrent sweep Eico 460 Scope / Kluge of yours, so I think that with the former detected and metered RF , you would be much better off.
::::::::::::::
::::::::::::::
::::::::::::::
::::::::::::::Addenda:
::::::::::::::Noticed your new readings just at this posting time, and the bucolic local osc grid voltages reading. And have you confirmed that there is even any level oscillation by the taking of a portable xstr radios ferri-loop and placing it atop the osc coil winding and tune it off station just onto the very edge / sideband of a weaker ~1400-1740 kc AM station and then run the operating radio's tuning condenser across the bottom half of the AM band to see if even a weak heterodyning / birdie is heard on the xstr radio.
::::::::::::::
::::::::::::::Standing by for feed back
::::::::::::::
::::::::::::::
::::::::::::::73's de Edd
::::::::::::::
::::::::::::::
::::::::::::::
::::::::::::::
::::::::::::::
::::::::::::::
::::::::::::::
::::::::::::::
::::::::::::::
::::::::::::::
:::::::::::::::Marv and all,
:::::::::::::::
::::::::::::::: Here are the voltage readings on the 6A7 tube.
:::::::::::::::
:::::::::::::::Pins 1 & 7: 6.8 volts AC (Filament)
:::::::::::::::Pin 2: 107.5 v DC (Plate)
:::::::::::::::Pin 3: 43.5 volts DC (G3 and G5)
:::::::::::::::Pin 4: 106.7 volts (G2)
:::::::::::::::Pin 5: 2.2 V DC (G1)
:::::::::::::::Pin 6: 2.647 volts DC (Cathode)
:::::::::::::::Cap: -.361 v DC (G4)
:::::::::::::::
:::::::::::::::These seem like pretty healthy voltages to me. I don't see anything wrong there. The IF transformer is connecting B+ to the plate and the Oscillator coil is connecting B+ to to pin 4. So neither coil is open.
:::::::::::::::
:::::::::::::::I did notice that C17 was missing. I put it back and it might have made an improvement but not with the oscillator.
:::::::::::::::
:::::::::::::::Please if anyone has anymore ideas before I "attack" (very closely examine) the oscillator coil, please help.
:::::::::::::::
:::::::::::::::Thanks,
:::::::::::::::
:::::::::::::::Dave
:::::::::::::::
::::::::::::::::Marv,
:::::::::::::::: My RF signal generator modulates a 400 Hz tone on the 456 Kc carrier frequency when it's set to 456 Kc. The part of the radio that the signal generator is connected to is tune to exactly tuned to 456 Kc. It can receive 456 Kc and only 456 Kc. That "station" is received and I can blast the 400 Hz tone through the speaker of the radio. If I change the RF signal generator to another frequency, then no 400 Hz tone is heard. It is as perfectly aligned as I can get it. It may not have the best adjacent channel rejection but the signal is the strongest when the signal generator is set to 456 Kc.
:::::::::::::::: The front part of the radio is what I'm having trouble with, and NOT the 456 Kc area. The radio is not converting (moving) the received frequency to 456 Kc. I can hear 570 Kc near the low end of the band and 620 Kc near the high end of the band (I live right near the brodcast antennas for these stations). That's all it does. It absolutely refuses to oscillate under any circumstances. I have checked about all I can check. All is working and not working at the same time.
:::::::::::::::: The trimmers you are talking about are the oscillator trimmers that can only do anything, are only active, if the oscillator is working. I can put them in any position and they do nothing. They aren't shorted. They are perfectly good but not active because the oscillator is dead.
:::::::::::::::: C-18 is brand new. It doesn't have any problems. One end is connected to the chassis and the other end is connected to a resistor. R3. I'll double check that it's also connected to the dead oscillator coil. It's not open. It just refuses to oscillate. All 11 paper and 2 electrolytic capacitors have been replaced. The positives of the electrolytic capacitors connect to the same place and the negatives connect to two different places.
:::::::::::::::: I am getting close to removing the oscillator coil and replacing it or rewinding this one. If only I had the specs for this one. The part number on it is: 2DT200. Maybe someone has an Emerson specs book.
::::::::::::::::
::::::::::::::::Thanks,
::::::::::::::::
::::::::::::::::Dave
::::::::::::::::
:::::::::::::::::Dave,
:::::::::::::::::The oscillator has 2 trimmers in BC mode. One on the tuning cap (C-3) and the other at the rear (C-5), either of which could hamper operation if misadjusted. The one at C-3 is common to both SW and BC. Check C-18. Also, when you tested the IF, (456kHz) were you using signal levels low to moderate or high enough to blast through at any freq?
:::::::::::::::::
:::::::::::::::::marv
:::::::::::::::::
::::::::::::::::::Marv,
:::::::::::::::::: The resistors are the correct value. I checked them. I never replaced them. I also knew that the long black capacitor looking devices were also resistors. They are all correct. The capacitors are in the correct places. Nothing has been changed.
:::::::::::::::::: I'll check the voltage and double check for "birdies". I think I did hear them. My huge isolation transformer is getting a lot of use on this restoration.
::::::::::::::::::
::::::::::::::::::Thanks,
::::::::::::::::::
::::::::::::::::::Dave
::::::::::::::::::
:::::::::::::::::::Dave,
:::::::::::::::::::In reading your 2 posts, I assume the set never worked and you re-capped and replaced bad resistors first. In this case, did you replace the parts just as they were originally installed, but did you also verify their placement via the schematic?
:::::::::::::::::::
:::::::::::::::::::marv
:::::::::::::::::::
::::::::::::::::::::Radiodoc,
:::::::::::::::::::: I just tried that and it makes absolutely no difference whatsoever.
:::::::::::::::::::: What do I look at next?
::::::::::::::::::::
::::::::::::::::::::Thanks,
::::::::::::::::::::
:::::::::::::::::::::Dave,
:::::::::::::::::::::
:::::::::::::::::::::The 98 volts is probably ok. If all else failed and as a shot in the dark, I would reverse the coil leads on the non-tuned winding between B+ and the oscillator "plate" and see what happens.
:::::::::::::::::::::
:::::::::::::::::::::Radiodoc
:::::::::::::::::::::***************
:::::::::::::::::::::
::::::::::::::::::::::Radiodoc,
:::::::::::::::::::::: I took out the oscillator coil and checked every connection and all are good (Perfect), no opens. I checked and cleaned the band switch several times. I replaced C9 several times. When I connect 456 Kc to it from my RF signal generator, it receives that tone perfectly. It blasts!! But it wont take what's presented to it from the antenna terminals and convert that to 456 Kc. It absolutely refuses to do that under any circumstances.
:::::::::::::::::::::: I checked all the connections and they are perfectly perfectly perfect. The resistors are all the correct values. The solder connections have been re-done and they are nice and shiny.
:::::::::::::::::::::: I tried 3 different 6A7 tubes and none of them make any difference.
:::::::::::::::::::::: I checked to make sure that the tuning capacitor or trimmer have any shorts on the oscillator side and there are no shorts. When the set is on and I try to adjust the oscillator screw or short the rotor with the stator on the oscillator side it makes no difference at all. All it's doing is "TRFing". The person who owns this radio MUST have the radio working immediately. I must continue working on it until it works. What do I do next? How do I convert it to a TRF receiver?
::::::::::::::::::::::
::::::::::::::::::::::Thanks,
::::::::::::::::::::::
::::::::::::::::::::::Dave
:::::::::::::::::::::::Radiodoc,
::::::::::::::::::::::: B+ is 98 volts. Is that low? Shouldn't it be a little higher? I can't see any way to raise it. Filament voltage on the 6A7 is 5.3 volts.
:::::::::::::::::::::::
:::::::::::::::::::::::Thanks,
:::::::::::::::::::::::
:::::::::::::::::::::::Dave
::::::::::::::::::::::::Radiodoc,
:::::::::::::::::::::::: C9 is a 100 pf capacitor. I replaced it and it made absolutely no difference.
::::::::::::::::::::::::
::::::::::::::::::::::::Dave
:::::::::::::::::::::::::Dave,
:::::::::::::::::::::::::
:::::::::::::::::::::::::If all fails, walk away for a while and then come back and check carefully all the wiring around the osc circuit for correctness and good solder joints. Did you check C9 (probably a mica)or replace it. If not may try substituting another. Voltage checks on the stage may give a clue if any are off very much.
:::::::::::::::::::::::::
:::::::::::::::::::::::::Radiodoc
:::::::::::::::::::::::::***********
:::::::::::::::::::::::::
:::::::::::::::::::::::::
::::::::::::::::::::::::::Hello All,
:::::::::::::::::::::::::: I have checked everything and the oscillator absolutely refuses to work. All paper and filter capacitors have been replaced. No part of the oscillator coil is open. The resistors are good. I tried a few 6A7s and it still wont work. What to I look at next?
:::::::::::::::::::::::::: This is an AC/DC set. There's not that much there.
::::::::::::::::::::::::::
::::::::::::::::::::::::::Thanks,
::::::::::::::::::::::::::
::::::::::::::::::::::::::Dave
I substituted the IF transformers for for the oscillator coil. I didn't replace the IF transformer because it works fine. This is taking much much too long. There must be some reason why this circuit absolutely refuses to oscillate.
Thanks,
Dave
:Bill VA,
: C19 doesn't connect to the chassis. Who said that it does? I don't have 82 volts anymore. It's 115 or 116 and the oscillator is still dead. I have tried various oscillator coils and substituted IF transformers and it's still dead dead dead.
: The voltage on pin 5 with the last IF transformer I tried, was 2.8 volts. Pin 6 was 3 volts.
: What do I try next? I have replaced and cleaned cleaned cleaned all the switch contacts several times. I have tried 7 6A7s. Replaced all the resistors. I have tried different C9s, and it still absolutely refuses to oscillate. The only thing I can do is use my RF signal generator as the oscillator. Then the voltage on pin 5 goes negative. Nothing else can get it to do that. What's going on? I don't think that the owner of the radio wants to have an RF signal generator attached to it permanently.
:THere must be something left to replace. But what?
:
:Thanks,
:
:Dave
::Dave, to me your B+ is low even before it drops to 82V. The schematic indicates voltage readings at 117. I would at least expect B+ on today's line voltage to be higher rather than lower tho 98 sounds ok if steady. I would take the voltage measurements as stated accross the field coil and the choke. C19 does not connect to the chassis. I used to tell my boys when working on dirt bikes or cars, look for something simple causing the problem. I did come home a couple times and parts be laying everywhere...waiting on me. I think you have tried about everything and I know it gets aggravating. But you'll get it and we all will say ahhh.
::Bill VA
::Bill VA
::
::
:::Bill,
:::
::: I replaced all the resistors and I still have a very dead oscillator.
:::
:::Dave
::::Dave, You didn't leave any of those old resistors in place? My next try...replace them all regardless of the readings.
::::Bill VA
::::
:::::Bill,
::::: C8 is brand new. It is a bypass capacitor. The old waxy one was removed from the radio about a week ago. The circuit updates don't seem to have anything to do with the oscillator. The 456 Kc part of the radio works fine.
::::: When I attempted to look at C8, R9 (500K), in another part of the radio, fell apart. Also one of the leads fell off of a flexible resistor R2. So I had to replace them. I re-soldered the wire C8 wire to the 6A7 pin and it made absolutely no difference. The oscillator is still dead.
:::::
::::: I do notice now that when the set is on a while, the B+ voltage goes down to 85 volts. These are brand new filter capacitors. So that cannot be the problem. I'll just have to replace every resistor, including the flexible ones. Those crimps onto the carbon must all be failing. I have tons of NOS old style resistors.
:::::The Oscillator is still Dead Dead Dead.
::::: I'll replace the resistors and let everyone know if the oscillator starts to work. It will probably never work. I'll also try 7 or 8 more 6A7s.
::::: What should I look at next?
:::::
:::::Thanks,
:::::
:::::Dave
::::::Dave, I'm too slow (both ways) to keep up with this thread. But I got to wade in. C-8 is one to recheck, off the 6A7 screen. Also, just curious, did you need to make the changes to R-9, 11, & 12, and C-13 & 14 based on your serial number?
::::::
::::::Bill VA
::::::
::::::
:::::::Radiodoc,
::::::: I just looked through the archives and found that if the voltage is positive it means that the oscillator is not operating. This is what I have been trying to tell you. The oscillator is dead. Ok, good, now we have absolute proof that the oscillator is dead. Now what do I look for? There could still be something not working. The oscillator coil? There is continuity but I don't know what it's value is in micro-henries. All I know is that it's a transformer. It has two primaries for the two bands, and one secondary. The part number on the oscillator coil 2DT200 matches the number in the service data. So it is original.
::::::: I'll keep checking the archives to see what others have done in this situation. I think that this may be a common problem. If you know what to check please let me know.
:::::::
:::::::Thanks,
:::::::
:::::::Dave
::::::::
::::::::Radiodoc,
:::::::: Yes, it is positive. Pin 5 is 2.4 volts and pin 6 is 2.8 volts now. The only pins that are negative are the filament pins which are -23 volts DC with respect to the chassis. But they are 6.8 volts AC when I measure across the filament.
:::::::: Is there something else wrong elsewhere in the set that's preventing the oscillator from working?
::::::::
::::::::Thanks,
::::::::
::::::::Dave
::::::::
:::::::::Radiodoc,
::::::::: It was 2.2 volts and it wasn't minus. What would be wrong if it's positive?
::::::::: I'm going to double check that voltage.
:::::::::
:::::::::Thanks,
:::::::::
:::::::::Dave
::::::::::Dave,
::::::::::
::::::::::With the radio off did you try measuring between adjacent pins (with tube removed) to see if possibly there is an arc over between pins. You mentioned there was 2 volts on the oscillator grid. There should be a negative voltage on the oscillator grid unless you forgot to type a minus sign in front of the voltage reading you posted.
::::::::::
::::::::::Radiodoc
::::::::::************
::::::::::
:::::::::::Marv,
::::::::::: The connections and the voltages are quite good. But it still wont oscillate. It works and absolutely refuses to work all at the same time.
:::::::::::
:::::::::::Thanks,
:::::::::::
:::::::::::Dave
::::::::::::Marv,
:::::::::::: Yes they are. I measure the pin and the contact and I get the same reading from both. But I'll double check.
::::::::::::
::::::::::::Thanks,
::::::::::::
::::::::::::Dave
:::::::::::::Dave,
:::::::::::::You have eliminated almost everything. There is one remaining item though. Are you sure the socket/tube pin connections are firm?
:::::::::::::
:::::::::::::marv
:::::::::::::
::::::::::::::Edd,
:::::::::::::: This oscillator is dead, dead, dead. A transistor radio will pick up nothing from it. Also, the radio works exactly the same way whether the oscillator coil is connected to the oscillator side of the tuning capacitor or not. No difference. It absolutely refuses to oscillate even though all is connected perfectly. All components are good too (except for I believe, the oscillator coil). I have more than qadruple checked the 30K, 50K, and 300 whatever ohm resistors. They are hooked up correctly. Also, the another 100pf capacitor was tried and it makes no difference. It's still dead dead dead.
:::::::::::::: I don't quite understand what you want me to do with the B & K. But I was able to use the B & K to "tune" the radio in the CW position. The rest of the radio receives the 460 Kc perfectly. So it's ready for the oscillator/mixer circuit to work. I am getting ready to replace the oscillator coil. I think I can take one from another AC/DC set just to try it out. Can I do that? I see the that there is a B+ side (output) and the other side that connects to the oscillator side of the tuning capacitor. I think that the second I replace the oscillator coil it will work perfectly. Please correct me if I'm wrong.
:::::::::::::: The oscillator coil has two sections on it. One is the Litz wire and the other is the enameled wire.
:::::::::::::: I think that what you want me to do at the junction of c1 and R9 is to inject an oscillation to see if I can then tune the radio normally with its tuning capacitor.
::::::::::::::
::::::::::::::Thanks,
::::::::::::::
::::::::::::::Dave
:::::::::::::::
:::::::::::::::
:::::::::::::::
:::::::::::::::
:::::::::::::::After reviewing your last postings info:
:::::::::::::::My fustus “querstion” was if the radio operated in some degree of receiving stations ? via a tunable superheterodyne action / mode prior to the mass recapping of the unit ?
:::::::::::::::
:::::::::::::::
:::::::::::::::
:::::::::::::::Can we assume that C9..100 mmfd was ok and not even messed with ?
:::::::::::::::Is cathode resistor R2 wired up ok and at its ~350 ohm value ?
:::::::::::::::As well as the grid resistor of R1 ….50k wired properly and at its value ?
:::::::::::::::The last item which I am sure that you did get involved with was the cathode bypass Condenser C7….05 ufd and it is OK and was reinstalled to the correct terminals…right…as that is also as critical as the 3 companion items.
:::::::::::::::
:::::::::::::::
:::::::::::::::
:::::::::::::::Looks as if the oscillator coil is on the larger ½ to ¾ in coil form and and a Litz wound unit in a tight layer…rather than the old style of enameled wire wound the full length of a long coil form. Plus, you seem to attest of its wirings continuity integrity as well as the adjunct tuning cap and its trimmer caps not being shorted out or dragging plates. Plus the additional reverting of one of the windings for a proper feed back phase check.
:::::::::::::::Also with your BEE und KAY, you should be able to couple its input into the first grid of the mixer and at the proper injection of CW RF level, be able to swing its dial thru the 1005-2195 khc range and tune thru your stronger receptive stations in the area, with the two “TRF” stations being the powerhouses, BUT with the necessity of having to manually tune the tuning condenser in order to optimize the RF section being in resonance with them, when trying for weaker stations in bringing up received reception level..
:::::::::::::::
:::::::::::::::
:::::::::::::::
:::::::::::::::To further ease your mind about the radios oscillator sections L-C combinations , you could go to the juncture of C9 and R1 and couple in CW RF via a series / isolative ~100 pf cap and go to the same junction and tack on an anode of a 1N34 / 60 / 64 / 270 GERMANIUM diode and at its cathodes end , take a .001 cap for bypassing to ground and then meter the cathodes output via a VTVM.
:::::::::::::::
:::::::::::::::
:::::::::::::::(N0…1N 914’s/4148’s/1N400oseries for this application)(Radio Shack stocks them in case you don’t have one from an oooold generation AM transistor radio chassis or from the building of a crystal set.)
:::::::::::::::
:::::::::::::::
:::::::::::::::
:::::::::::::::Then if you will power up the BEE und KAY and place in its CW mode and set the Emerson…(No power required....as this testing will be passive)…to the 1/3 lower end of the dial 700 kc ish (tuning cap ~ ¾ meshed)
:::::::::::::::Then you tune the B & K in the ~1000-1400 range and see if the co-joined parasitic tuned oscillators circuit doesn’t give you a rising / declining reading as resonance was scanned across.
:::::::::::::::Then, hop the radios tuning up to the higher third of the band (tuning cap ~ 1/4 meshed) and test for a like reading of a viable resonant circuit pair working at that
:::::::::::::::frequency also.
:::::::::::::::Thereby you have merely temp- rigged up a “po boys” grid dipper to interpret the presence of a functioning / resonating effect by the osc sections variable L-C pair and it having some degree of “Q”.
:::::::::::::::
:::::::::::::::
:::::::::::::::The other alternative being that recurrent sweep Eico 460 Scope / Kluge of yours, so I think that with the former detected and metered RF , you would be much better off.
:::::::::::::::
:::::::::::::::
:::::::::::::::
:::::::::::::::Addenda:
:::::::::::::::Noticed your new readings just at this posting time, and the bucolic local osc grid voltages reading. And have you confirmed that there is even any level oscillation by the taking of a portable xstr radios ferri-loop and placing it atop the osc coil winding and tune it off station just onto the very edge / sideband of a weaker ~1400-1740 kc AM station and then run the operating radio's tuning condenser across the bottom half of the AM band to see if even a weak heterodyning / birdie is heard on the xstr radio.
:::::::::::::::
:::::::::::::::Standing by for feed back
:::::::::::::::
:::::::::::::::
:::::::::::::::73's de Edd
:::::::::::::::
:::::::::::::::
:::::::::::::::
:::::::::::::::
:::::::::::::::
:::::::::::::::
:::::::::::::::
:::::::::::::::
:::::::::::::::
:::::::::::::::
::::::::::::::::Marv and all,
::::::::::::::::
:::::::::::::::: Here are the voltage readings on the 6A7 tube.
::::::::::::::::
::::::::::::::::Pins 1 & 7: 6.8 volts AC (Filament)
::::::::::::::::Pin 2: 107.5 v DC (Plate)
::::::::::::::::Pin 3: 43.5 volts DC (G3 and G5)
::::::::::::::::Pin 4: 106.7 volts (G2)
::::::::::::::::Pin 5: 2.2 V DC (G1)
::::::::::::::::Pin 6: 2.647 volts DC (Cathode)
::::::::::::::::Cap: -.361 v DC (G4)
::::::::::::::::
::::::::::::::::These seem like pretty healthy voltages to me. I don't see anything wrong there. The IF transformer is connecting B+ to the plate and the Oscillator coil is connecting B+ to to pin 4. So neither coil is open.
::::::::::::::::
::::::::::::::::I did notice that C17 was missing. I put it back and it might have made an improvement but not with the oscillator.
::::::::::::::::
::::::::::::::::Please if anyone has anymore ideas before I "attack" (very closely examine) the oscillator coil, please help.
::::::::::::::::
::::::::::::::::Thanks,
::::::::::::::::
::::::::::::::::Dave
::::::::::::::::
:::::::::::::::::Marv,
::::::::::::::::: My RF signal generator modulates a 400 Hz tone on the 456 Kc carrier frequency when it's set to 456 Kc. The part of the radio that the signal generator is connected to is tune to exactly tuned to 456 Kc. It can receive 456 Kc and only 456 Kc. That "station" is received and I can blast the 400 Hz tone through the speaker of the radio. If I change the RF signal generator to another frequency, then no 400 Hz tone is heard. It is as perfectly aligned as I can get it. It may not have the best adjacent channel rejection but the signal is the strongest when the signal generator is set to 456 Kc.
::::::::::::::::: The front part of the radio is what I'm having trouble with, and NOT the 456 Kc area. The radio is not converting (moving) the received frequency to 456 Kc. I can hear 570 Kc near the low end of the band and 620 Kc near the high end of the band (I live right near the brodcast antennas for these stations). That's all it does. It absolutely refuses to oscillate under any circumstances. I have checked about all I can check. All is working and not working at the same time.
::::::::::::::::: The trimmers you are talking about are the oscillator trimmers that can only do anything, are only active, if the oscillator is working. I can put them in any position and they do nothing. They aren't shorted. They are perfectly good but not active because the oscillator is dead.
::::::::::::::::: C-18 is brand new. It doesn't have any problems. One end is connected to the chassis and the other end is connected to a resistor. R3. I'll double check that it's also connected to the dead oscillator coil. It's not open. It just refuses to oscillate. All 11 paper and 2 electrolytic capacitors have been replaced. The positives of the electrolytic capacitors connect to the same place and the negatives connect to two different places.
::::::::::::::::: I am getting close to removing the oscillator coil and replacing it or rewinding this one. If only I had the specs for this one. The part number on it is: 2DT200. Maybe someone has an Emerson specs book.
:::::::::::::::::
:::::::::::::::::Thanks,
:::::::::::::::::
:::::::::::::::::Dave
:::::::::::::::::
::::::::::::::::::Dave,
::::::::::::::::::The oscillator has 2 trimmers in BC mode. One on the tuning cap (C-3) and the other at the rear (C-5), either of which could hamper operation if misadjusted. The one at C-3 is common to both SW and BC. Check C-18. Also, when you tested the IF, (456kHz) were you using signal levels low to moderate or high enough to blast through at any freq?
::::::::::::::::::
::::::::::::::::::marv
::::::::::::::::::
:::::::::::::::::::Marv,
::::::::::::::::::: The resistors are the correct value. I checked them. I never replaced them. I also knew that the long black capacitor looking devices were also resistors. They are all correct. The capacitors are in the correct places. Nothing has been changed.
::::::::::::::::::: I'll check the voltage and double check for "birdies". I think I did hear them. My huge isolation transformer is getting a lot of use on this restoration.
:::::::::::::::::::
:::::::::::::::::::Thanks,
:::::::::::::::::::
:::::::::::::::::::Dave
:::::::::::::::::::
::::::::::::::::::::Dave,
::::::::::::::::::::In reading your 2 posts, I assume the set never worked and you re-capped and replaced bad resistors first. In this case, did you replace the parts just as they were originally installed, but did you also verify their placement via the schematic?
::::::::::::::::::::
::::::::::::::::::::marv
::::::::::::::::::::
:::::::::::::::::::::Radiodoc,
::::::::::::::::::::: I just tried that and it makes absolutely no difference whatsoever.
::::::::::::::::::::: What do I look at next?
:::::::::::::::::::::
:::::::::::::::::::::Thanks,
:::::::::::::::::::::
::::::::::::::::::::::Dave,
::::::::::::::::::::::
::::::::::::::::::::::The 98 volts is probably ok. If all else failed and as a shot in the dark, I would reverse the coil leads on the non-tuned winding between B+ and the oscillator "plate" and see what happens.
::::::::::::::::::::::
::::::::::::::::::::::Radiodoc
::::::::::::::::::::::***************
::::::::::::::::::::::
:::::::::::::::::::::::Radiodoc,
::::::::::::::::::::::: I took out the oscillator coil and checked every connection and all are good (Perfect), no opens. I checked and cleaned the band switch several times. I replaced C9 several times. When I connect 456 Kc to it from my RF signal generator, it receives that tone perfectly. It blasts!! But it wont take what's presented to it from the antenna terminals and convert that to 456 Kc. It absolutely refuses to do that under any circumstances.
::::::::::::::::::::::: I checked all the connections and they are perfectly perfectly perfect. The resistors are all the correct values. The solder connections have been re-done and they are nice and shiny.
::::::::::::::::::::::: I tried 3 different 6A7 tubes and none of them make any difference.
::::::::::::::::::::::: I checked to make sure that the tuning capacitor or trimmer have any shorts on the oscillator side and there are no shorts. When the set is on and I try to adjust the oscillator screw or short the rotor with the stator on the oscillator side it makes no difference at all. All it's doing is "TRFing". The person who owns this radio MUST have the radio working immediately. I must continue working on it until it works. What do I do next? How do I convert it to a TRF receiver?
:::::::::::::::::::::::
:::::::::::::::::::::::Thanks,
:::::::::::::::::::::::
:::::::::::::::::::::::Dave
::::::::::::::::::::::::Radiodoc,
:::::::::::::::::::::::: B+ is 98 volts. Is that low? Shouldn't it be a little higher? I can't see any way to raise it. Filament voltage on the 6A7 is 5.3 volts.
::::::::::::::::::::::::
::::::::::::::::::::::::Thanks,
::::::::::::::::::::::::
::::::::::::::::::::::::Dave
:::::::::::::::::::::::::Radiodoc,
::::::::::::::::::::::::: C9 is a 100 pf capacitor. I replaced it and it made absolutely no difference.
:::::::::::::::::::::::::
:::::::::::::::::::::::::Dave
::::::::::::::::::::::::::Dave,
::::::::::::::::::::::::::
::::::::::::::::::::::::::If all fails, walk away for a while and then come back and check carefully all the wiring around the osc circuit for correctness and good solder joints. Did you check C9 (probably a mica)or replace it. If not may try substituting another. Voltage checks on the stage may give a clue if any are off very much.
::::::::::::::::::::::::::
::::::::::::::::::::::::::Radiodoc
::::::::::::::::::::::::::***********
::::::::::::::::::::::::::
::::::::::::::::::::::::::
:::::::::::::::::::::::::::Hello All,
::::::::::::::::::::::::::: I have checked everything and the oscillator absolutely refuses to work. All paper and filter capacitors have been replaced. No part of the oscillator coil is open. The resistors are good. I tried a few 6A7s and it still wont work. What to I look at next?
::::::::::::::::::::::::::: This is an AC/DC set. There's not that much there.
:::::::::::::::::::::::::::
:::::::::::::::::::::::::::Thanks,
:::::::::::::::::::::::::::
:::::::::::::::::::::::::::Dave
I don't see the need for a large antenna but I don't know what you mean about that either. But "even if the oscillator coil is disconnected from the oscillator side of the tuning capacitor" smacks of an open. I see where you have clean the sw contacts etc. I believe you need to take some point-to-point resistance readings from antenna thru osc coil. You are having this problem on both bands and I wouldn't rule out a connection to that band switch, for sure if you coil reads good.
Bill VA
Bill VA,
: I substituted the IF transformers for for the oscillator coil. I didn't replace the IF transformer because it works fine. This is taking much much too long. There must be some reason why this circuit absolutely refuses to oscillate.
:
:Thanks,
:
:Dave
::Bill VA,
:: C19 doesn't connect to the chassis. Who said that it does? I don't have 82 volts anymore. It's 115 or 116 and the oscillator is still dead. I have tried various oscillator coils and substituted IF transformers and it's still dead dead dead.
:: The voltage on pin 5 with the last IF transformer I tried, was 2.8 volts. Pin 6 was 3 volts.
:: What do I try next? I have replaced and cleaned cleaned cleaned all the switch contacts several times. I have tried 7 6A7s. Replaced all the resistors. I have tried different C9s, and it still absolutely refuses to oscillate. The only thing I can do is use my RF signal generator as the oscillator. Then the voltage on pin 5 goes negative. Nothing else can get it to do that. What's going on? I don't think that the owner of the radio wants to have an RF signal generator attached to it permanently.
::THere must be something left to replace. But what?
::
::Thanks,
::
::Dave
:::Dave, to me your B+ is low even before it drops to 82V. The schematic indicates voltage readings at 117. I would at least expect B+ on today's line voltage to be higher rather than lower tho 98 sounds ok if steady. I would take the voltage measurements as stated accross the field coil and the choke. C19 does not connect to the chassis. I used to tell my boys when working on dirt bikes or cars, look for something simple causing the problem. I did come home a couple times and parts be laying everywhere...waiting on me. I think you have tried about everything and I know it gets aggravating. But you'll get it and we all will say ahhh.
:::Bill VA
:::Bill VA
:::
:::
::::Bill,
::::
:::: I replaced all the resistors and I still have a very dead oscillator.
::::
::::Dave
:::::Dave, You didn't leave any of those old resistors in place? My next try...replace them all regardless of the readings.
:::::Bill VA
:::::
::::::Bill,
:::::: C8 is brand new. It is a bypass capacitor. The old waxy one was removed from the radio about a week ago. The circuit updates don't seem to have anything to do with the oscillator. The 456 Kc part of the radio works fine.
:::::: When I attempted to look at C8, R9 (500K), in another part of the radio, fell apart. Also one of the leads fell off of a flexible resistor R2. So I had to replace them. I re-soldered the wire C8 wire to the 6A7 pin and it made absolutely no difference. The oscillator is still dead.
::::::
:::::: I do notice now that when the set is on a while, the B+ voltage goes down to 85 volts. These are brand new filter capacitors. So that cannot be the problem. I'll just have to replace every resistor, including the flexible ones. Those crimps onto the carbon must all be failing. I have tons of NOS old style resistors.
::::::The Oscillator is still Dead Dead Dead.
:::::: I'll replace the resistors and let everyone know if the oscillator starts to work. It will probably never work. I'll also try 7 or 8 more 6A7s.
:::::: What should I look at next?
::::::
::::::Thanks,
::::::
::::::Dave
:::::::Dave, I'm too slow (both ways) to keep up with this thread. But I got to wade in. C-8 is one to recheck, off the 6A7 screen. Also, just curious, did you need to make the changes to R-9, 11, & 12, and C-13 & 14 based on your serial number?
:::::::
:::::::Bill VA
:::::::
:::::::
::::::::Radiodoc,
:::::::: I just looked through the archives and found that if the voltage is positive it means that the oscillator is not operating. This is what I have been trying to tell you. The oscillator is dead. Ok, good, now we have absolute proof that the oscillator is dead. Now what do I look for? There could still be something not working. The oscillator coil? There is continuity but I don't know what it's value is in micro-henries. All I know is that it's a transformer. It has two primaries for the two bands, and one secondary. The part number on the oscillator coil 2DT200 matches the number in the service data. So it is original.
:::::::: I'll keep checking the archives to see what others have done in this situation. I think that this may be a common problem. If you know what to check please let me know.
::::::::
::::::::Thanks,
::::::::
::::::::Dave
:::::::::
:::::::::Radiodoc,
::::::::: Yes, it is positive. Pin 5 is 2.4 volts and pin 6 is 2.8 volts now. The only pins that are negative are the filament pins which are -23 volts DC with respect to the chassis. But they are 6.8 volts AC when I measure across the filament.
::::::::: Is there something else wrong elsewhere in the set that's preventing the oscillator from working?
:::::::::
:::::::::Thanks,
:::::::::
:::::::::Dave
:::::::::
::::::::::Radiodoc,
:::::::::: It was 2.2 volts and it wasn't minus. What would be wrong if it's positive?
:::::::::: I'm going to double check that voltage.
::::::::::
::::::::::Thanks,
::::::::::
::::::::::Dave
:::::::::::Dave,
:::::::::::
:::::::::::With the radio off did you try measuring between adjacent pins (with tube removed) to see if possibly there is an arc over between pins. You mentioned there was 2 volts on the oscillator grid. There should be a negative voltage on the oscillator grid unless you forgot to type a minus sign in front of the voltage reading you posted.
:::::::::::
:::::::::::Radiodoc
:::::::::::************
:::::::::::
::::::::::::Marv,
:::::::::::: The connections and the voltages are quite good. But it still wont oscillate. It works and absolutely refuses to work all at the same time.
::::::::::::
::::::::::::Thanks,
::::::::::::
::::::::::::Dave
:::::::::::::Marv,
::::::::::::: Yes they are. I measure the pin and the contact and I get the same reading from both. But I'll double check.
:::::::::::::
:::::::::::::Thanks,
:::::::::::::
:::::::::::::Dave
::::::::::::::Dave,
::::::::::::::You have eliminated almost everything. There is one remaining item though. Are you sure the socket/tube pin connections are firm?
::::::::::::::
::::::::::::::marv
::::::::::::::
:::::::::::::::Edd,
::::::::::::::: This oscillator is dead, dead, dead. A transistor radio will pick up nothing from it. Also, the radio works exactly the same way whether the oscillator coil is connected to the oscillator side of the tuning capacitor or not. No difference. It absolutely refuses to oscillate even though all is connected perfectly. All components are good too (except for I believe, the oscillator coil). I have more than qadruple checked the 30K, 50K, and 300 whatever ohm resistors. They are hooked up correctly. Also, the another 100pf capacitor was tried and it makes no difference. It's still dead dead dead.
::::::::::::::: I don't quite understand what you want me to do with the B & K. But I was able to use the B & K to "tune" the radio in the CW position. The rest of the radio receives the 460 Kc perfectly. So it's ready for the oscillator/mixer circuit to work. I am getting ready to replace the oscillator coil. I think I can take one from another AC/DC set just to try it out. Can I do that? I see the that there is a B+ side (output) and the other side that connects to the oscillator side of the tuning capacitor. I think that the second I replace the oscillator coil it will work perfectly. Please correct me if I'm wrong.
::::::::::::::: The oscillator coil has two sections on it. One is the Litz wire and the other is the enameled wire.
::::::::::::::: I think that what you want me to do at the junction of c1 and R9 is to inject an oscillation to see if I can then tune the radio normally with its tuning capacitor.
:::::::::::::::
:::::::::::::::Thanks,
:::::::::::::::
:::::::::::::::Dave
::::::::::::::::
::::::::::::::::
::::::::::::::::
::::::::::::::::
::::::::::::::::After reviewing your last postings info:
::::::::::::::::My fustus “querstion” was if the radio operated in some degree of receiving stations ? via a tunable superheterodyne action / mode prior to the mass recapping of the unit ?
::::::::::::::::
::::::::::::::::
::::::::::::::::
::::::::::::::::Can we assume that C9..100 mmfd was ok and not even messed with ?
::::::::::::::::Is cathode resistor R2 wired up ok and at its ~350 ohm value ?
::::::::::::::::As well as the grid resistor of R1 ….50k wired properly and at its value ?
::::::::::::::::The last item which I am sure that you did get involved with was the cathode bypass Condenser C7….05 ufd and it is OK and was reinstalled to the correct terminals…right…as that is also as critical as the 3 companion items.
::::::::::::::::
::::::::::::::::
::::::::::::::::
::::::::::::::::Looks as if the oscillator coil is on the larger ½ to ¾ in coil form and and a Litz wound unit in a tight layer…rather than the old style of enameled wire wound the full length of a long coil form. Plus, you seem to attest of its wirings continuity integrity as well as the adjunct tuning cap and its trimmer caps not being shorted out or dragging plates. Plus the additional reverting of one of the windings for a proper feed back phase check.
::::::::::::::::Also with your BEE und KAY, you should be able to couple its input into the first grid of the mixer and at the proper injection of CW RF level, be able to swing its dial thru the 1005-2195 khc range and tune thru your stronger receptive stations in the area, with the two “TRF” stations being the powerhouses, BUT with the necessity of having to manually tune the tuning condenser in order to optimize the RF section being in resonance with them, when trying for weaker stations in bringing up received reception level..
::::::::::::::::
::::::::::::::::
::::::::::::::::
::::::::::::::::To further ease your mind about the radios oscillator sections L-C combinations , you could go to the juncture of C9 and R1 and couple in CW RF via a series / isolative ~100 pf cap and go to the same junction and tack on an anode of a 1N34 / 60 / 64 / 270 GERMANIUM diode and at its cathodes end , take a .001 cap for bypassing to ground and then meter the cathodes output via a VTVM.
::::::::::::::::
::::::::::::::::
::::::::::::::::(N0…1N 914’s/4148’s/1N400oseries for this application)(Radio Shack stocks them in case you don’t have one from an oooold generation AM transistor radio chassis or from the building of a crystal set.)
::::::::::::::::
::::::::::::::::
::::::::::::::::
::::::::::::::::Then if you will power up the BEE und KAY and place in its CW mode and set the Emerson…(No power required....as this testing will be passive)…to the 1/3 lower end of the dial 700 kc ish (tuning cap ~ ¾ meshed)
::::::::::::::::Then you tune the B & K in the ~1000-1400 range and see if the co-joined parasitic tuned oscillators circuit doesn’t give you a rising / declining reading as resonance was scanned across.
::::::::::::::::Then, hop the radios tuning up to the higher third of the band (tuning cap ~ 1/4 meshed) and test for a like reading of a viable resonant circuit pair working at that
::::::::::::::::frequency also.
::::::::::::::::Thereby you have merely temp- rigged up a “po boys” grid dipper to interpret the presence of a functioning / resonating effect by the osc sections variable L-C pair and it having some degree of “Q”.
::::::::::::::::
::::::::::::::::
::::::::::::::::The other alternative being that recurrent sweep Eico 460 Scope / Kluge of yours, so I think that with the former detected and metered RF , you would be much better off.
::::::::::::::::
::::::::::::::::
::::::::::::::::
::::::::::::::::Addenda:
::::::::::::::::Noticed your new readings just at this posting time, and the bucolic local osc grid voltages reading. And have you confirmed that there is even any level oscillation by the taking of a portable xstr radios ferri-loop and placing it atop the osc coil winding and tune it off station just onto the very edge / sideband of a weaker ~1400-1740 kc AM station and then run the operating radio's tuning condenser across the bottom half of the AM band to see if even a weak heterodyning / birdie is heard on the xstr radio.
::::::::::::::::
::::::::::::::::Standing by for feed back
::::::::::::::::
::::::::::::::::
::::::::::::::::73's de Edd
::::::::::::::::
::::::::::::::::
::::::::::::::::
::::::::::::::::
::::::::::::::::
::::::::::::::::
::::::::::::::::
::::::::::::::::
::::::::::::::::
::::::::::::::::
:::::::::::::::::Marv and all,
:::::::::::::::::
::::::::::::::::: Here are the voltage readings on the 6A7 tube.
:::::::::::::::::
:::::::::::::::::Pins 1 & 7: 6.8 volts AC (Filament)
:::::::::::::::::Pin 2: 107.5 v DC (Plate)
:::::::::::::::::Pin 3: 43.5 volts DC (G3 and G5)
:::::::::::::::::Pin 4: 106.7 volts (G2)
:::::::::::::::::Pin 5: 2.2 V DC (G1)
:::::::::::::::::Pin 6: 2.647 volts DC (Cathode)
:::::::::::::::::Cap: -.361 v DC (G4)
:::::::::::::::::
:::::::::::::::::These seem like pretty healthy voltages to me. I don't see anything wrong there. The IF transformer is connecting B+ to the plate and the Oscillator coil is connecting B+ to to pin 4. So neither coil is open.
:::::::::::::::::
:::::::::::::::::I did notice that C17 was missing. I put it back and it might have made an improvement but not with the oscillator.
:::::::::::::::::
:::::::::::::::::Please if anyone has anymore ideas before I "attack" (very closely examine) the oscillator coil, please help.
:::::::::::::::::
:::::::::::::::::Thanks,
:::::::::::::::::
:::::::::::::::::Dave
:::::::::::::::::
::::::::::::::::::Marv,
:::::::::::::::::: My RF signal generator modulates a 400 Hz tone on the 456 Kc carrier frequency when it's set to 456 Kc. The part of the radio that the signal generator is connected to is tune to exactly tuned to 456 Kc. It can receive 456 Kc and only 456 Kc. That "station" is received and I can blast the 400 Hz tone through the speaker of the radio. If I change the RF signal generator to another frequency, then no 400 Hz tone is heard. It is as perfectly aligned as I can get it. It may not have the best adjacent channel rejection but the signal is the strongest when the signal generator is set to 456 Kc.
:::::::::::::::::: The front part of the radio is what I'm having trouble with, and NOT the 456 Kc area. The radio is not converting (moving) the received frequency to 456 Kc. I can hear 570 Kc near the low end of the band and 620 Kc near the high end of the band (I live right near the brodcast antennas for these stations). That's all it does. It absolutely refuses to oscillate under any circumstances. I have checked about all I can check. All is working and not working at the same time.
:::::::::::::::::: The trimmers you are talking about are the oscillator trimmers that can only do anything, are only active, if the oscillator is working. I can put them in any position and they do nothing. They aren't shorted. They are perfectly good but not active because the oscillator is dead.
:::::::::::::::::: C-18 is brand new. It doesn't have any problems. One end is connected to the chassis and the other end is connected to a resistor. R3. I'll double check that it's also connected to the dead oscillator coil. It's not open. It just refuses to oscillate. All 11 paper and 2 electrolytic capacitors have been replaced. The positives of the electrolytic capacitors connect to the same place and the negatives connect to two different places.
:::::::::::::::::: I am getting close to removing the oscillator coil and replacing it or rewinding this one. If only I had the specs for this one. The part number on it is: 2DT200. Maybe someone has an Emerson specs book.
::::::::::::::::::
::::::::::::::::::Thanks,
::::::::::::::::::
::::::::::::::::::Dave
::::::::::::::::::
:::::::::::::::::::Dave,
:::::::::::::::::::The oscillator has 2 trimmers in BC mode. One on the tuning cap (C-3) and the other at the rear (C-5), either of which could hamper operation if misadjusted. The one at C-3 is common to both SW and BC. Check C-18. Also, when you tested the IF, (456kHz) were you using signal levels low to moderate or high enough to blast through at any freq?
:::::::::::::::::::
:::::::::::::::::::marv
:::::::::::::::::::
::::::::::::::::::::Marv,
:::::::::::::::::::: The resistors are the correct value. I checked them. I never replaced them. I also knew that the long black capacitor looking devices were also resistors. They are all correct. The capacitors are in the correct places. Nothing has been changed.
:::::::::::::::::::: I'll check the voltage and double check for "birdies". I think I did hear them. My huge isolation transformer is getting a lot of use on this restoration.
::::::::::::::::::::
::::::::::::::::::::Thanks,
::::::::::::::::::::
::::::::::::::::::::Dave
::::::::::::::::::::
:::::::::::::::::::::Dave,
:::::::::::::::::::::In reading your 2 posts, I assume the set never worked and you re-capped and replaced bad resistors first. In this case, did you replace the parts just as they were originally installed, but did you also verify their placement via the schematic?
:::::::::::::::::::::
:::::::::::::::::::::marv
:::::::::::::::::::::
::::::::::::::::::::::Radiodoc,
:::::::::::::::::::::: I just tried that and it makes absolutely no difference whatsoever.
:::::::::::::::::::::: What do I look at next?
::::::::::::::::::::::
::::::::::::::::::::::Thanks,
::::::::::::::::::::::
:::::::::::::::::::::::Dave,
:::::::::::::::::::::::
:::::::::::::::::::::::The 98 volts is probably ok. If all else failed and as a shot in the dark, I would reverse the coil leads on the non-tuned winding between B+ and the oscillator "plate" and see what happens.
:::::::::::::::::::::::
:::::::::::::::::::::::Radiodoc
:::::::::::::::::::::::***************
:::::::::::::::::::::::
::::::::::::::::::::::::Radiodoc,
:::::::::::::::::::::::: I took out the oscillator coil and checked every connection and all are good (Perfect), no opens. I checked and cleaned the band switch several times. I replaced C9 several times. When I connect 456 Kc to it from my RF signal generator, it receives that tone perfectly. It blasts!! But it wont take what's presented to it from the antenna terminals and convert that to 456 Kc. It absolutely refuses to do that under any circumstances.
:::::::::::::::::::::::: I checked all the connections and they are perfectly perfectly perfect. The resistors are all the correct values. The solder connections have been re-done and they are nice and shiny.
:::::::::::::::::::::::: I tried 3 different 6A7 tubes and none of them make any difference.
:::::::::::::::::::::::: I checked to make sure that the tuning capacitor or trimmer have any shorts on the oscillator side and there are no shorts. When the set is on and I try to adjust the oscillator screw or short the rotor with the stator on the oscillator side it makes no difference at all. All it's doing is "TRFing". The person who owns this radio MUST have the radio working immediately. I must continue working on it until it works. What do I do next? How do I convert it to a TRF receiver?
::::::::::::::::::::::::
::::::::::::::::::::::::Thanks,
::::::::::::::::::::::::
::::::::::::::::::::::::Dave
:::::::::::::::::::::::::Radiodoc,
::::::::::::::::::::::::: B+ is 98 volts. Is that low? Shouldn't it be a little higher? I can't see any way to raise it. Filament voltage on the 6A7 is 5.3 volts.
:::::::::::::::::::::::::
:::::::::::::::::::::::::Thanks,
:::::::::::::::::::::::::
:::::::::::::::::::::::::Dave
::::::::::::::::::::::::::Radiodoc,
:::::::::::::::::::::::::: C9 is a 100 pf capacitor. I replaced it and it made absolutely no difference.
::::::::::::::::::::::::::
::::::::::::::::::::::::::Dave
:::::::::::::::::::::::::::Dave,
:::::::::::::::::::::::::::
:::::::::::::::::::::::::::If all fails, walk away for a while and then come back and check carefully all the wiring around the osc circuit for correctness and good solder joints. Did you check C9 (probably a mica)or replace it. If not may try substituting another. Voltage checks on the stage may give a clue if any are off very much.
:::::::::::::::::::::::::::
:::::::::::::::::::::::::::Radiodoc
:::::::::::::::::::::::::::***********
:::::::::::::::::::::::::::
:::::::::::::::::::::::::::
::::::::::::::::::::::::::::Hello All,
:::::::::::::::::::::::::::: I have checked everything and the oscillator absolutely refuses to work. All paper and filter capacitors have been replaced. No part of the oscillator coil is open. The resistors are good. I tried a few 6A7s and it still wont work. What to I look at next?
:::::::::::::::::::::::::::: This is an AC/DC set. There's not that much there.
::::::::::::::::::::::::::::
::::::::::::::::::::::::::::Thanks,
::::::::::::::::::::::::::::
::::::::::::::::::::::::::::Dave
Is the radio still using the linecord resistor or has it been replaced and a 145 Ohm resistor substituted in its place. Is it possible the plates of the 25Z5 have been wired to the wrong side of the resistor? What is the AC voltage on the plates of the 25Z5 referenced to the other side of the line. It looks as though it should be the full line voltage of 120 volts.
Radiodoc
***********
:Bill,
:
: I replaced all the resistors and I still have a very dead oscillator.
:
:Dave
::Dave, You didn't leave any of those old resistors in place? My next try...replace them all regardless of the readings.
::Bill VA
::
:::Bill,
::: C8 is brand new. It is a bypass capacitor. The old waxy one was removed from the radio about a week ago. The circuit updates don't seem to have anything to do with the oscillator. The 456 Kc part of the radio works fine.
::: When I attempted to look at C8, R9 (500K), in another part of the radio, fell apart. Also one of the leads fell off of a flexible resistor R2. So I had to replace them. I re-soldered the wire C8 wire to the 6A7 pin and it made absolutely no difference. The oscillator is still dead.
:::
::: I do notice now that when the set is on a while, the B+ voltage goes down to 85 volts. These are brand new filter capacitors. So that cannot be the problem. I'll just have to replace every resistor, including the flexible ones. Those crimps onto the carbon must all be failing. I have tons of NOS old style resistors.
:::The Oscillator is still Dead Dead Dead.
::: I'll replace the resistors and let everyone know if the oscillator starts to work. It will probably never work. I'll also try 7 or 8 more 6A7s.
::: What should I look at next?
:::
:::Thanks,
:::
:::Dave
::::Dave, I'm too slow (both ways) to keep up with this thread. But I got to wade in. C-8 is one to recheck, off the 6A7 screen. Also, just curious, did you need to make the changes to R-9, 11, & 12, and C-13 & 14 based on your serial number?
::::
::::Bill VA
::::
::::
:::::Radiodoc,
::::: I just looked through the archives and found that if the voltage is positive it means that the oscillator is not operating. This is what I have been trying to tell you. The oscillator is dead. Ok, good, now we have absolute proof that the oscillator is dead. Now what do I look for? There could still be something not working. The oscillator coil? There is continuity but I don't know what it's value is in micro-henries. All I know is that it's a transformer. It has two primaries for the two bands, and one secondary. The part number on the oscillator coil 2DT200 matches the number in the service data. So it is original.
::::: I'll keep checking the archives to see what others have done in this situation. I think that this may be a common problem. If you know what to check please let me know.
:::::
:::::Thanks,
:::::
:::::Dave
::::::
::::::Radiodoc,
:::::: Yes, it is positive. Pin 5 is 2.4 volts and pin 6 is 2.8 volts now. The only pins that are negative are the filament pins which are -23 volts DC with respect to the chassis. But they are 6.8 volts AC when I measure across the filament.
:::::: Is there something else wrong elsewhere in the set that's preventing the oscillator from working?
::::::
::::::Thanks,
::::::
::::::Dave
::::::
:::::::Radiodoc,
::::::: It was 2.2 volts and it wasn't minus. What would be wrong if it's positive?
::::::: I'm going to double check that voltage.
:::::::
:::::::Thanks,
:::::::
:::::::Dave
::::::::Dave,
::::::::
::::::::With the radio off did you try measuring between adjacent pins (with tube removed) to see if possibly there is an arc over between pins. You mentioned there was 2 volts on the oscillator grid. There should be a negative voltage on the oscillator grid unless you forgot to type a minus sign in front of the voltage reading you posted.
::::::::
::::::::Radiodoc
::::::::************
::::::::
:::::::::Marv,
::::::::: The connections and the voltages are quite good. But it still wont oscillate. It works and absolutely refuses to work all at the same time.
:::::::::
:::::::::Thanks,
:::::::::
:::::::::Dave
::::::::::Marv,
:::::::::: Yes they are. I measure the pin and the contact and I get the same reading from both. But I'll double check.
::::::::::
::::::::::Thanks,
::::::::::
::::::::::Dave
:::::::::::Dave,
:::::::::::You have eliminated almost everything. There is one remaining item though. Are you sure the socket/tube pin connections are firm?
:::::::::::
:::::::::::marv
:::::::::::
::::::::::::Edd,
:::::::::::: This oscillator is dead, dead, dead. A transistor radio will pick up nothing from it. Also, the radio works exactly the same way whether the oscillator coil is connected to the oscillator side of the tuning capacitor or not. No difference. It absolutely refuses to oscillate even though all is connected perfectly. All components are good too (except for I believe, the oscillator coil). I have more than qadruple checked the 30K, 50K, and 300 whatever ohm resistors. They are hooked up correctly. Also, the another 100pf capacitor was tried and it makes no difference. It's still dead dead dead.
:::::::::::: I don't quite understand what you want me to do with the B & K. But I was able to use the B & K to "tune" the radio in the CW position. The rest of the radio receives the 460 Kc perfectly. So it's ready for the oscillator/mixer circuit to work. I am getting ready to replace the oscillator coil. I think I can take one from another AC/DC set just to try it out. Can I do that? I see the that there is a B+ side (output) and the other side that connects to the oscillator side of the tuning capacitor. I think that the second I replace the oscillator coil it will work perfectly. Please correct me if I'm wrong.
:::::::::::: The oscillator coil has two sections on it. One is the Litz wire and the other is the enameled wire.
:::::::::::: I think that what you want me to do at the junction of c1 and R9 is to inject an oscillation to see if I can then tune the radio normally with its tuning capacitor.
::::::::::::
::::::::::::Thanks,
::::::::::::
::::::::::::Dave
:::::::::::::
:::::::::::::
:::::::::::::
:::::::::::::
:::::::::::::After reviewing your last postings info:
:::::::::::::My fustus “querstion” was if the radio operated in some degree of receiving stations ? via a tunable superheterodyne action / mode prior to the mass recapping of the unit ?
:::::::::::::
:::::::::::::
:::::::::::::
:::::::::::::Can we assume that C9..100 mmfd was ok and not even messed with ?
:::::::::::::Is cathode resistor R2 wired up ok and at its ~350 ohm value ?
:::::::::::::As well as the grid resistor of R1 ….50k wired properly and at its value ?
:::::::::::::The last item which I am sure that you did get involved with was the cathode bypass Condenser C7….05 ufd and it is OK and was reinstalled to the correct terminals…right…as that is also as critical as the 3 companion items.
:::::::::::::
:::::::::::::
:::::::::::::
:::::::::::::Looks as if the oscillator coil is on the larger ½ to ¾ in coil form and and a Litz wound unit in a tight layer…rather than the old style of enameled wire wound the full length of a long coil form. Plus, you seem to attest of its wirings continuity integrity as well as the adjunct tuning cap and its trimmer caps not being shorted out or dragging plates. Plus the additional reverting of one of the windings for a proper feed back phase check.
:::::::::::::Also with your BEE und KAY, you should be able to couple its input into the first grid of the mixer and at the proper injection of CW RF level, be able to swing its dial thru the 1005-2195 khc range and tune thru your stronger receptive stations in the area, with the two “TRF” stations being the powerhouses, BUT with the necessity of having to manually tune the tuning condenser in order to optimize the RF section being in resonance with them, when trying for weaker stations in bringing up received reception level..
:::::::::::::
:::::::::::::
:::::::::::::
:::::::::::::To further ease your mind about the radios oscillator sections L-C combinations , you could go to the juncture of C9 and R1 and couple in CW RF via a series / isolative ~100 pf cap and go to the same junction and tack on an anode of a 1N34 / 60 / 64 / 270 GERMANIUM diode and at its cathodes end , take a .001 cap for bypassing to ground and then meter the cathodes output via a VTVM.
:::::::::::::
:::::::::::::
:::::::::::::(N0…1N 914’s/4148’s/1N400oseries for this application)(Radio Shack stocks them in case you don’t have one from an oooold generation AM transistor radio chassis or from the building of a crystal set.)
:::::::::::::
:::::::::::::
:::::::::::::
:::::::::::::Then if you will power up the BEE und KAY and place in its CW mode and set the Emerson…(No power required....as this testing will be passive)…to the 1/3 lower end of the dial 700 kc ish (tuning cap ~ ¾ meshed)
:::::::::::::Then you tune the B & K in the ~1000-1400 range and see if the co-joined parasitic tuned oscillators circuit doesn’t give you a rising / declining reading as resonance was scanned across.
:::::::::::::Then, hop the radios tuning up to the higher third of the band (tuning cap ~ 1/4 meshed) and test for a like reading of a viable resonant circuit pair working at that
:::::::::::::frequency also.
:::::::::::::Thereby you have merely temp- rigged up a “po boys” grid dipper to interpret the presence of a functioning / resonating effect by the osc sections variable L-C pair and it having some degree of “Q”.
:::::::::::::
:::::::::::::
:::::::::::::The other alternative being that recurrent sweep Eico 460 Scope / Kluge of yours, so I think that with the former detected and metered RF , you would be much better off.
:::::::::::::
:::::::::::::
:::::::::::::
:::::::::::::Addenda:
:::::::::::::Noticed your new readings just at this posting time, and the bucolic local osc grid voltages reading. And have you confirmed that there is even any level oscillation by the taking of a portable xstr radios ferri-loop and placing it atop the osc coil winding and tune it off station just onto the very edge / sideband of a weaker ~1400-1740 kc AM station and then run the operating radio's tuning condenser across the bottom half of the AM band to see if even a weak heterodyning / birdie is heard on the xstr radio.
:::::::::::::
:::::::::::::Standing by for feed back
:::::::::::::
:::::::::::::
:::::::::::::73's de Edd
:::::::::::::
:::::::::::::
:::::::::::::
:::::::::::::
:::::::::::::
:::::::::::::
:::::::::::::
:::::::::::::
:::::::::::::
:::::::::::::
::::::::::::::Marv and all,
::::::::::::::
:::::::::::::: Here are the voltage readings on the 6A7 tube.
::::::::::::::
::::::::::::::Pins 1 & 7: 6.8 volts AC (Filament)
::::::::::::::Pin 2: 107.5 v DC (Plate)
::::::::::::::Pin 3: 43.5 volts DC (G3 and G5)
::::::::::::::Pin 4: 106.7 volts (G2)
::::::::::::::Pin 5: 2.2 V DC (G1)
::::::::::::::Pin 6: 2.647 volts DC (Cathode)
::::::::::::::Cap: -.361 v DC (G4)
::::::::::::::
::::::::::::::These seem like pretty healthy voltages to me. I don't see anything wrong there. The IF transformer is connecting B+ to the plate and the Oscillator coil is connecting B+ to to pin 4. So neither coil is open.
::::::::::::::
::::::::::::::I did notice that C17 was missing. I put it back and it might have made an improvement but not with the oscillator.
::::::::::::::
::::::::::::::Please if anyone has anymore ideas before I "attack" (very closely examine) the oscillator coil, please help.
::::::::::::::
::::::::::::::Thanks,
::::::::::::::
::::::::::::::Dave
::::::::::::::
:::::::::::::::Marv,
::::::::::::::: My RF signal generator modulates a 400 Hz tone on the 456 Kc carrier frequency when it's set to 456 Kc. The part of the radio that the signal generator is connected to is tune to exactly tuned to 456 Kc. It can receive 456 Kc and only 456 Kc. That "station" is received and I can blast the 400 Hz tone through the speaker of the radio. If I change the RF signal generator to another frequency, then no 400 Hz tone is heard. It is as perfectly aligned as I can get it. It may not have the best adjacent channel rejection but the signal is the strongest when the signal generator is set to 456 Kc.
::::::::::::::: The front part of the radio is what I'm having trouble with, and NOT the 456 Kc area. The radio is not converting (moving) the received frequency to 456 Kc. I can hear 570 Kc near the low end of the band and 620 Kc near the high end of the band (I live right near the brodcast antennas for these stations). That's all it does. It absolutely refuses to oscillate under any circumstances. I have checked about all I can check. All is working and not working at the same time.
::::::::::::::: The trimmers you are talking about are the oscillator trimmers that can only do anything, are only active, if the oscillator is working. I can put them in any position and they do nothing. They aren't shorted. They are perfectly good but not active because the oscillator is dead.
::::::::::::::: C-18 is brand new. It doesn't have any problems. One end is connected to the chassis and the other end is connected to a resistor. R3. I'll double check that it's also connected to the dead oscillator coil. It's not open. It just refuses to oscillate. All 11 paper and 2 electrolytic capacitors have been replaced. The positives of the electrolytic capacitors connect to the same place and the negatives connect to two different places.
::::::::::::::: I am getting close to removing the oscillator coil and replacing it or rewinding this one. If only I had the specs for this one. The part number on it is: 2DT200. Maybe someone has an Emerson specs book.
:::::::::::::::
:::::::::::::::Thanks,
:::::::::::::::
:::::::::::::::Dave
:::::::::::::::
::::::::::::::::Dave,
::::::::::::::::The oscillator has 2 trimmers in BC mode. One on the tuning cap (C-3) and the other at the rear (C-5), either of which could hamper operation if misadjusted. The one at C-3 is common to both SW and BC. Check C-18. Also, when you tested the IF, (456kHz) were you using signal levels low to moderate or high enough to blast through at any freq?
::::::::::::::::
::::::::::::::::marv
::::::::::::::::
:::::::::::::::::Marv,
::::::::::::::::: The resistors are the correct value. I checked them. I never replaced them. I also knew that the long black capacitor looking devices were also resistors. They are all correct. The capacitors are in the correct places. Nothing has been changed.
::::::::::::::::: I'll check the voltage and double check for "birdies". I think I did hear them. My huge isolation transformer is getting a lot of use on this restoration.
:::::::::::::::::
:::::::::::::::::Thanks,
:::::::::::::::::
:::::::::::::::::Dave
:::::::::::::::::
::::::::::::::::::Dave,
::::::::::::::::::In reading your 2 posts, I assume the set never worked and you re-capped and replaced bad resistors first. In this case, did you replace the parts just as they were originally installed, but did you also verify their placement via the schematic?
::::::::::::::::::
::::::::::::::::::marv
::::::::::::::::::
:::::::::::::::::::Radiodoc,
::::::::::::::::::: I just tried that and it makes absolutely no difference whatsoever.
::::::::::::::::::: What do I look at next?
:::::::::::::::::::
:::::::::::::::::::Thanks,
:::::::::::::::::::
::::::::::::::::::::Dave,
::::::::::::::::::::
::::::::::::::::::::The 98 volts is probably ok. If all else failed and as a shot in the dark, I would reverse the coil leads on the non-tuned winding between B+ and the oscillator "plate" and see what happens.
::::::::::::::::::::
::::::::::::::::::::Radiodoc
::::::::::::::::::::***************
::::::::::::::::::::
:::::::::::::::::::::Radiodoc,
::::::::::::::::::::: I took out the oscillator coil and checked every connection and all are good (Perfect), no opens. I checked and cleaned the band switch several times. I replaced C9 several times. When I connect 456 Kc to it from my RF signal generator, it receives that tone perfectly. It blasts!! But it wont take what's presented to it from the antenna terminals and convert that to 456 Kc. It absolutely refuses to do that under any circumstances.
::::::::::::::::::::: I checked all the connections and they are perfectly perfectly perfect. The resistors are all the correct values. The solder connections have been re-done and they are nice and shiny.
::::::::::::::::::::: I tried 3 different 6A7 tubes and none of them make any difference.
::::::::::::::::::::: I checked to make sure that the tuning capacitor or trimmer have any shorts on the oscillator side and there are no shorts. When the set is on and I try to adjust the oscillator screw or short the rotor with the stator on the oscillator side it makes no difference at all. All it's doing is "TRFing". The person who owns this radio MUST have the radio working immediately. I must continue working on it until it works. What do I do next? How do I convert it to a TRF receiver?
:::::::::::::::::::::
:::::::::::::::::::::Thanks,
:::::::::::::::::::::
:::::::::::::::::::::Dave
::::::::::::::::::::::Radiodoc,
:::::::::::::::::::::: B+ is 98 volts. Is that low? Shouldn't it be a little higher? I can't see any way to raise it. Filament voltage on the 6A7 is 5.3 volts.
::::::::::::::::::::::
::::::::::::::::::::::Thanks,
::::::::::::::::::::::
::::::::::::::::::::::Dave
:::::::::::::::::::::::Radiodoc,
::::::::::::::::::::::: C9 is a 100 pf capacitor. I replaced it and it made absolutely no difference.
:::::::::::::::::::::::
:::::::::::::::::::::::Dave
::::::::::::::::::::::::Dave,
::::::::::::::::::::::::
::::::::::::::::::::::::If all fails, walk away for a while and then come back and check carefully all the wiring around the osc circuit for correctness and good solder joints. Did you check C9 (probably a mica)or replace it. If not may try substituting another. Voltage checks on the stage may give a clue if any are off very much.
::::::::::::::::::::::::
::::::::::::::::::::::::Radiodoc
::::::::::::::::::::::::***********
::::::::::::::::::::::::
::::::::::::::::::::::::
:::::::::::::::::::::::::Hello All,
::::::::::::::::::::::::: I have checked everything and the oscillator absolutely refuses to work. All paper and filter capacitors have been replaced. No part of the oscillator coil is open. The resistors are good. I tried a few 6A7s and it still wont work. What to I look at next?
::::::::::::::::::::::::: This is an AC/DC set. There's not that much there.
:::::::::::::::::::::::::
:::::::::::::::::::::::::Thanks,
:::::::::::::::::::::::::
:::::::::::::::::::::::::Dave
The original resistor cord is fine. No, it's not hooked up on the wrong side of the resistor. Yes, 116 is the voltage reading I get.
Thanks,
Dave
:Dave,
:
:Is the radio still using the linecord resistor or has it been replaced and a 145 Ohm resistor substituted in its place. Is it possible the plates of the 25Z5 have been wired to the wrong side of the resistor? What is the AC voltage on the plates of the 25Z5 referenced to the other side of the line. It looks as though it should be the full line voltage of 120 volts.
:
:Radiodoc
:***********
:
::Bill,
::
:: I replaced all the resistors and I still have a very dead oscillator.
::
::Dave
:::Dave, You didn't leave any of those old resistors in place? My next try...replace them all regardless of the readings.
:::Bill VA
:::
::::Bill,
:::: C8 is brand new. It is a bypass capacitor. The old waxy one was removed from the radio about a week ago. The circuit updates don't seem to have anything to do with the oscillator. The 456 Kc part of the radio works fine.
:::: When I attempted to look at C8, R9 (500K), in another part of the radio, fell apart. Also one of the leads fell off of a flexible resistor R2. So I had to replace them. I re-soldered the wire C8 wire to the 6A7 pin and it made absolutely no difference. The oscillator is still dead.
::::
:::: I do notice now that when the set is on a while, the B+ voltage goes down to 85 volts. These are brand new filter capacitors. So that cannot be the problem. I'll just have to replace every resistor, including the flexible ones. Those crimps onto the carbon must all be failing. I have tons of NOS old style resistors.
::::The Oscillator is still Dead Dead Dead.
:::: I'll replace the resistors and let everyone know if the oscillator starts to work. It will probably never work. I'll also try 7 or 8 more 6A7s.
:::: What should I look at next?
::::
::::Thanks,
::::
::::Dave
:::::Dave, I'm too slow (both ways) to keep up with this thread. But I got to wade in. C-8 is one to recheck, off the 6A7 screen. Also, just curious, did you need to make the changes to R-9, 11, & 12, and C-13 & 14 based on your serial number?
:::::
:::::Bill VA
:::::
:::::
::::::Radiodoc,
:::::: I just looked through the archives and found that if the voltage is positive it means that the oscillator is not operating. This is what I have been trying to tell you. The oscillator is dead. Ok, good, now we have absolute proof that the oscillator is dead. Now what do I look for? There could still be something not working. The oscillator coil? There is continuity but I don't know what it's value is in micro-henries. All I know is that it's a transformer. It has two primaries for the two bands, and one secondary. The part number on the oscillator coil 2DT200 matches the number in the service data. So it is original.
:::::: I'll keep checking the archives to see what others have done in this situation. I think that this may be a common problem. If you know what to check please let me know.
::::::
::::::Thanks,
::::::
::::::Dave
:::::::
:::::::Radiodoc,
::::::: Yes, it is positive. Pin 5 is 2.4 volts and pin 6 is 2.8 volts now. The only pins that are negative are the filament pins which are -23 volts DC with respect to the chassis. But they are 6.8 volts AC when I measure across the filament.
::::::: Is there something else wrong elsewhere in the set that's preventing the oscillator from working?
:::::::
:::::::Thanks,
:::::::
:::::::Dave
:::::::
::::::::Radiodoc,
:::::::: It was 2.2 volts and it wasn't minus. What would be wrong if it's positive?
:::::::: I'm going to double check that voltage.
::::::::
::::::::Thanks,
::::::::
::::::::Dave
:::::::::Dave,
:::::::::
:::::::::With the radio off did you try measuring between adjacent pins (with tube removed) to see if possibly there is an arc over between pins. You mentioned there was 2 volts on the oscillator grid. There should be a negative voltage on the oscillator grid unless you forgot to type a minus sign in front of the voltage reading you posted.
:::::::::
:::::::::Radiodoc
:::::::::************
:::::::::
::::::::::Marv,
:::::::::: The connections and the voltages are quite good. But it still wont oscillate. It works and absolutely refuses to work all at the same time.
::::::::::
::::::::::Thanks,
::::::::::
::::::::::Dave
:::::::::::Marv,
::::::::::: Yes they are. I measure the pin and the contact and I get the same reading from both. But I'll double check.
:::::::::::
:::::::::::Thanks,
:::::::::::
:::::::::::Dave
::::::::::::Dave,
::::::::::::You have eliminated almost everything. There is one remaining item though. Are you sure the socket/tube pin connections are firm?
::::::::::::
::::::::::::marv
::::::::::::
:::::::::::::Edd,
::::::::::::: This oscillator is dead, dead, dead. A transistor radio will pick up nothing from it. Also, the radio works exactly the same way whether the oscillator coil is connected to the oscillator side of the tuning capacitor or not. No difference. It absolutely refuses to oscillate even though all is connected perfectly. All components are good too (except for I believe, the oscillator coil). I have more than qadruple checked the 30K, 50K, and 300 whatever ohm resistors. They are hooked up correctly. Also, the another 100pf capacitor was tried and it makes no difference. It's still dead dead dead.
::::::::::::: I don't quite understand what you want me to do with the B & K. But I was able to use the B & K to "tune" the radio in the CW position. The rest of the radio receives the 460 Kc perfectly. So it's ready for the oscillator/mixer circuit to work. I am getting ready to replace the oscillator coil. I think I can take one from another AC/DC set just to try it out. Can I do that? I see the that there is a B+ side (output) and the other side that connects to the oscillator side of the tuning capacitor. I think that the second I replace the oscillator coil it will work perfectly. Please correct me if I'm wrong.
::::::::::::: The oscillator coil has two sections on it. One is the Litz wire and the other is the enameled wire.
::::::::::::: I think that what you want me to do at the junction of c1 and R9 is to inject an oscillation to see if I can then tune the radio normally with its tuning capacitor.
:::::::::::::
:::::::::::::Thanks,
:::::::::::::
:::::::::::::Dave
::::::::::::::
::::::::::::::
::::::::::::::
::::::::::::::
::::::::::::::After reviewing your last postings info:
::::::::::::::My fustus “querstion” was if the radio operated in some degree of receiving stations ? via a tunable superheterodyne action / mode prior to the mass recapping of the unit ?
::::::::::::::
::::::::::::::
::::::::::::::
::::::::::::::Can we assume that C9..100 mmfd was ok and not even messed with ?
::::::::::::::Is cathode resistor R2 wired up ok and at its ~350 ohm value ?
::::::::::::::As well as the grid resistor of R1 ….50k wired properly and at its value ?
::::::::::::::The last item which I am sure that you did get involved with was the cathode bypass Condenser C7….05 ufd and it is OK and was reinstalled to the correct terminals…right…as that is also as critical as the 3 companion items.
::::::::::::::
::::::::::::::
::::::::::::::
::::::::::::::Looks as if the oscillator coil is on the larger ½ to ¾ in coil form and and a Litz wound unit in a tight layer…rather than the old style of enameled wire wound the full length of a long coil form. Plus, you seem to attest of its wirings continuity integrity as well as the adjunct tuning cap and its trimmer caps not being shorted out or dragging plates. Plus the additional reverting of one of the windings for a proper feed back phase check.
::::::::::::::Also with your BEE und KAY, you should be able to couple its input into the first grid of the mixer and at the proper injection of CW RF level, be able to swing its dial thru the 1005-2195 khc range and tune thru your stronger receptive stations in the area, with the two “TRF” stations being the powerhouses, BUT with the necessity of having to manually tune the tuning condenser in order to optimize the RF section being in resonance with them, when trying for weaker stations in bringing up received reception level..
::::::::::::::
::::::::::::::
::::::::::::::
::::::::::::::To further ease your mind about the radios oscillator sections L-C combinations , you could go to the juncture of C9 and R1 and couple in CW RF via a series / isolative ~100 pf cap and go to the same junction and tack on an anode of a 1N34 / 60 / 64 / 270 GERMANIUM diode and at its cathodes end , take a .001 cap for bypassing to ground and then meter the cathodes output via a VTVM.
::::::::::::::
::::::::::::::
::::::::::::::(N0…1N 914’s/4148’s/1N400oseries for this application)(Radio Shack stocks them in case you don’t have one from an oooold generation AM transistor radio chassis or from the building of a crystal set.)
::::::::::::::
::::::::::::::
::::::::::::::
::::::::::::::Then if you will power up the BEE und KAY and place in its CW mode and set the Emerson…(No power required....as this testing will be passive)…to the 1/3 lower end of the dial 700 kc ish (tuning cap ~ ¾ meshed)
::::::::::::::Then you tune the B & K in the ~1000-1400 range and see if the co-joined parasitic tuned oscillators circuit doesn’t give you a rising / declining reading as resonance was scanned across.
::::::::::::::Then, hop the radios tuning up to the higher third of the band (tuning cap ~ 1/4 meshed) and test for a like reading of a viable resonant circuit pair working at that
::::::::::::::frequency also.
::::::::::::::Thereby you have merely temp- rigged up a “po boys” grid dipper to interpret the presence of a functioning / resonating effect by the osc sections variable L-C pair and it having some degree of “Q”.
::::::::::::::
::::::::::::::
::::::::::::::The other alternative being that recurrent sweep Eico 460 Scope / Kluge of yours, so I think that with the former detected and metered RF , you would be much better off.
::::::::::::::
::::::::::::::
::::::::::::::
::::::::::::::Addenda:
::::::::::::::Noticed your new readings just at this posting time, and the bucolic local osc grid voltages reading. And have you confirmed that there is even any level oscillation by the taking of a portable xstr radios ferri-loop and placing it atop the osc coil winding and tune it off station just onto the very edge / sideband of a weaker ~1400-1740 kc AM station and then run the operating radio's tuning condenser across the bottom half of the AM band to see if even a weak heterodyning / birdie is heard on the xstr radio.
::::::::::::::
::::::::::::::Standing by for feed back
::::::::::::::
::::::::::::::
::::::::::::::73's de Edd
::::::::::::::
::::::::::::::
::::::::::::::
::::::::::::::
::::::::::::::
::::::::::::::
::::::::::::::
::::::::::::::
::::::::::::::
::::::::::::::
:::::::::::::::Marv and all,
:::::::::::::::
::::::::::::::: Here are the voltage readings on the 6A7 tube.
:::::::::::::::
:::::::::::::::Pins 1 & 7: 6.8 volts AC (Filament)
:::::::::::::::Pin 2: 107.5 v DC (Plate)
:::::::::::::::Pin 3: 43.5 volts DC (G3 and G5)
:::::::::::::::Pin 4: 106.7 volts (G2)
:::::::::::::::Pin 5: 2.2 V DC (G1)
:::::::::::::::Pin 6: 2.647 volts DC (Cathode)
:::::::::::::::Cap: -.361 v DC (G4)
:::::::::::::::
:::::::::::::::These seem like pretty healthy voltages to me. I don't see anything wrong there. The IF transformer is connecting B+ to the plate and the Oscillator coil is connecting B+ to to pin 4. So neither coil is open.
:::::::::::::::
:::::::::::::::I did notice that C17 was missing. I put it back and it might have made an improvement but not with the oscillator.
:::::::::::::::
:::::::::::::::Please if anyone has anymore ideas before I "attack" (very closely examine) the oscillator coil, please help.
:::::::::::::::
:::::::::::::::Thanks,
:::::::::::::::
:::::::::::::::Dave
:::::::::::::::
::::::::::::::::Marv,
:::::::::::::::: My RF signal generator modulates a 400 Hz tone on the 456 Kc carrier frequency when it's set to 456 Kc. The part of the radio that the signal generator is connected to is tune to exactly tuned to 456 Kc. It can receive 456 Kc and only 456 Kc. That "station" is received and I can blast the 400 Hz tone through the speaker of the radio. If I change the RF signal generator to another frequency, then no 400 Hz tone is heard. It is as perfectly aligned as I can get it. It may not have the best adjacent channel rejection but the signal is the strongest when the signal generator is set to 456 Kc.
:::::::::::::::: The front part of the radio is what I'm having trouble with, and NOT the 456 Kc area. The radio is not converting (moving) the received frequency to 456 Kc. I can hear 570 Kc near the low end of the band and 620 Kc near the high end of the band (I live right near the brodcast antennas for these stations). That's all it does. It absolutely refuses to oscillate under any circumstances. I have checked about all I can check. All is working and not working at the same time.
:::::::::::::::: The trimmers you are talking about are the oscillator trimmers that can only do anything, are only active, if the oscillator is working. I can put them in any position and they do nothing. They aren't shorted. They are perfectly good but not active because the oscillator is dead.
:::::::::::::::: C-18 is brand new. It doesn't have any problems. One end is connected to the chassis and the other end is connected to a resistor. R3. I'll double check that it's also connected to the dead oscillator coil. It's not open. It just refuses to oscillate. All 11 paper and 2 electrolytic capacitors have been replaced. The positives of the electrolytic capacitors connect to the same place and the negatives connect to two different places.
:::::::::::::::: I am getting close to removing the oscillator coil and replacing it or rewinding this one. If only I had the specs for this one. The part number on it is: 2DT200. Maybe someone has an Emerson specs book.
::::::::::::::::
::::::::::::::::Thanks,
::::::::::::::::
::::::::::::::::Dave
::::::::::::::::
:::::::::::::::::Dave,
:::::::::::::::::The oscillator has 2 trimmers in BC mode. One on the tuning cap (C-3) and the other at the rear (C-5), either of which could hamper operation if misadjusted. The one at C-3 is common to both SW and BC. Check C-18. Also, when you tested the IF, (456kHz) were you using signal levels low to moderate or high enough to blast through at any freq?
:::::::::::::::::
:::::::::::::::::marv
:::::::::::::::::
::::::::::::::::::Marv,
:::::::::::::::::: The resistors are the correct value. I checked them. I never replaced them. I also knew that the long black capacitor looking devices were also resistors. They are all correct. The capacitors are in the correct places. Nothing has been changed.
:::::::::::::::::: I'll check the voltage and double check for "birdies". I think I did hear them. My huge isolation transformer is getting a lot of use on this restoration.
::::::::::::::::::
::::::::::::::::::Thanks,
::::::::::::::::::
::::::::::::::::::Dave
::::::::::::::::::
:::::::::::::::::::Dave,
:::::::::::::::::::In reading your 2 posts, I assume the set never worked and you re-capped and replaced bad resistors first. In this case, did you replace the parts just as they were originally installed, but did you also verify their placement via the schematic?
:::::::::::::::::::
:::::::::::::::::::marv
:::::::::::::::::::
::::::::::::::::::::Radiodoc,
:::::::::::::::::::: I just tried that and it makes absolutely no difference whatsoever.
:::::::::::::::::::: What do I look at next?
::::::::::::::::::::
::::::::::::::::::::Thanks,
::::::::::::::::::::
:::::::::::::::::::::Dave,
:::::::::::::::::::::
:::::::::::::::::::::The 98 volts is probably ok. If all else failed and as a shot in the dark, I would reverse the coil leads on the non-tuned winding between B+ and the oscillator "plate" and see what happens.
:::::::::::::::::::::
:::::::::::::::::::::Radiodoc
:::::::::::::::::::::***************
:::::::::::::::::::::
::::::::::::::::::::::Radiodoc,
:::::::::::::::::::::: I took out the oscillator coil and checked every connection and all are good (Perfect), no opens. I checked and cleaned the band switch several times. I replaced C9 several times. When I connect 456 Kc to it from my RF signal generator, it receives that tone perfectly. It blasts!! But it wont take what's presented to it from the antenna terminals and convert that to 456 Kc. It absolutely refuses to do that under any circumstances.
:::::::::::::::::::::: I checked all the connections and they are perfectly perfectly perfect. The resistors are all the correct values. The solder connections have been re-done and they are nice and shiny.
:::::::::::::::::::::: I tried 3 different 6A7 tubes and none of them make any difference.
:::::::::::::::::::::: I checked to make sure that the tuning capacitor or trimmer have any shorts on the oscillator side and there are no shorts. When the set is on and I try to adjust the oscillator screw or short the rotor with the stator on the oscillator side it makes no difference at all. All it's doing is "TRFing". The person who owns this radio MUST have the radio working immediately. I must continue working on it until it works. What do I do next? How do I convert it to a TRF receiver?
::::::::::::::::::::::
::::::::::::::::::::::Thanks,
::::::::::::::::::::::
::::::::::::::::::::::Dave
:::::::::::::::::::::::Radiodoc,
::::::::::::::::::::::: B+ is 98 volts. Is that low? Shouldn't it be a little higher? I can't see any way to raise it. Filament voltage on the 6A7 is 5.3 volts.
:::::::::::::::::::::::
:::::::::::::::::::::::Thanks,
:::::::::::::::::::::::
:::::::::::::::::::::::Dave
::::::::::::::::::::::::Radiodoc,
:::::::::::::::::::::::: C9 is a 100 pf capacitor. I replaced it and it made absolutely no difference.
::::::::::::::::::::::::
::::::::::::::::::::::::Dave
:::::::::::::::::::::::::Dave,
:::::::::::::::::::::::::
:::::::::::::::::::::::::If all fails, walk away for a while and then come back and check carefully all the wiring around the osc circuit for correctness and good solder joints. Did you check C9 (probably a mica)or replace it. If not may try substituting another. Voltage checks on the stage may give a clue if any are off very much.
:::::::::::::::::::::::::
:::::::::::::::::::::::::Radiodoc
:::::::::::::::::::::::::***********
:::::::::::::::::::::::::
:::::::::::::::::::::::::
::::::::::::::::::::::::::Hello All,
:::::::::::::::::::::::::: I have checked everything and the oscillator absolutely refuses to work. All paper and filter capacitors have been replaced. No part of the oscillator coil is open. The resistors are good. I tried a few 6A7s and it still wont work. What to I look at next?
:::::::::::::::::::::::::: This is an AC/DC set. There's not that much there.
::::::::::::::::::::::::::
::::::::::::::::::::::::::Thanks,
::::::::::::::::::::::::::
::::::::::::::::::::::::::Dave
I noted the cathode (self bias) resistor on the parts list is wire wound, which would make it inductive. Have you yet/or tried replacing it with a standard carbon resistor?
marv
:Bill,
:
: I replaced all the resistors and I still have a very dead oscillator.
:
:Dave
::Dave, You didn't leave any of those old resistors in place? My next try...replace them all regardless of the readings.
::Bill VA
::
:::Bill,
::: C8 is brand new. It is a bypass capacitor. The old waxy one was removed from the radio about a week ago. The circuit updates don't seem to have anything to do with the oscillator. The 456 Kc part of the radio works fine.
::: When I attempted to look at C8, R9 (500K), in another part of the radio, fell apart. Also one of the leads fell off of a flexible resistor R2. So I had to replace them. I re-soldered the wire C8 wire to the 6A7 pin and it made absolutely no difference. The oscillator is still dead.
:::
::: I do notice now that when the set is on a while, the B+ voltage goes down to 85 volts. These are brand new filter capacitors. So that cannot be the problem. I'll just have to replace every resistor, including the flexible ones. Those crimps onto the carbon must all be failing. I have tons of NOS old style resistors.
:::The Oscillator is still Dead Dead Dead.
::: I'll replace the resistors and let everyone know if the oscillator starts to work. It will probably never work. I'll also try 7 or 8 more 6A7s.
::: What should I look at next?
:::
:::Thanks,
:::
:::Dave
::::Dave, I'm too slow (both ways) to keep up with this thread. But I got to wade in. C-8 is one to recheck, off the 6A7 screen. Also, just curious, did you need to make the changes to R-9, 11, & 12, and C-13 & 14 based on your serial number?
::::
::::Bill VA
::::
::::
:::::Radiodoc,
::::: I just looked through the archives and found that if the voltage is positive it means that the oscillator is not operating. This is what I have been trying to tell you. The oscillator is dead. Ok, good, now we have absolute proof that the oscillator is dead. Now what do I look for? There could still be something not working. The oscillator coil? There is continuity but I don't know what it's value is in micro-henries. All I know is that it's a transformer. It has two primaries for the two bands, and one secondary. The part number on the oscillator coil 2DT200 matches the number in the service data. So it is original.
::::: I'll keep checking the archives to see what others have done in this situation. I think that this may be a common problem. If you know what to check please let me know.
:::::
:::::Thanks,
:::::
:::::Dave
::::::
::::::Radiodoc,
:::::: Yes, it is positive. Pin 5 is 2.4 volts and pin 6 is 2.8 volts now. The only pins that are negative are the filament pins which are -23 volts DC with respect to the chassis. But they are 6.8 volts AC when I measure across the filament.
:::::: Is there something else wrong elsewhere in the set that's preventing the oscillator from working?
::::::
::::::Thanks,
::::::
::::::Dave
::::::
:::::::Radiodoc,
::::::: It was 2.2 volts and it wasn't minus. What would be wrong if it's positive?
::::::: I'm going to double check that voltage.
:::::::
:::::::Thanks,
:::::::
:::::::Dave
::::::::Dave,
::::::::
::::::::With the radio off did you try measuring between adjacent pins (with tube removed) to see if possibly there is an arc over between pins. You mentioned there was 2 volts on the oscillator grid. There should be a negative voltage on the oscillator grid unless you forgot to type a minus sign in front of the voltage reading you posted.
::::::::
::::::::Radiodoc
::::::::************
::::::::
:::::::::Marv,
::::::::: The connections and the voltages are quite good. But it still wont oscillate. It works and absolutely refuses to work all at the same time.
:::::::::
:::::::::Thanks,
:::::::::
:::::::::Dave
::::::::::Marv,
:::::::::: Yes they are. I measure the pin and the contact and I get the same reading from both. But I'll double check.
::::::::::
::::::::::Thanks,
::::::::::
::::::::::Dave
:::::::::::Dave,
:::::::::::You have eliminated almost everything. There is one remaining item though. Are you sure the socket/tube pin connections are firm?
:::::::::::
:::::::::::marv
:::::::::::
::::::::::::Edd,
:::::::::::: This oscillator is dead, dead, dead. A transistor radio will pick up nothing from it. Also, the radio works exactly the same way whether the oscillator coil is connected to the oscillator side of the tuning capacitor or not. No difference. It absolutely refuses to oscillate even though all is connected perfectly. All components are good too (except for I believe, the oscillator coil). I have more than qadruple checked the 30K, 50K, and 300 whatever ohm resistors. They are hooked up correctly. Also, the another 100pf capacitor was tried and it makes no difference. It's still dead dead dead.
:::::::::::: I don't quite understand what you want me to do with the B & K. But I was able to use the B & K to "tune" the radio in the CW position. The rest of the radio receives the 460 Kc perfectly. So it's ready for the oscillator/mixer circuit to work. I am getting ready to replace the oscillator coil. I think I can take one from another AC/DC set just to try it out. Can I do that? I see the that there is a B+ side (output) and the other side that connects to the oscillator side of the tuning capacitor. I think that the second I replace the oscillator coil it will work perfectly. Please correct me if I'm wrong.
:::::::::::: The oscillator coil has two sections on it. One is the Litz wire and the other is the enameled wire.
:::::::::::: I think that what you want me to do at the junction of c1 and R9 is to inject an oscillation to see if I can then tune the radio normally with its tuning capacitor.
::::::::::::
::::::::::::Thanks,
::::::::::::
::::::::::::Dave
:::::::::::::
:::::::::::::
:::::::::::::
:::::::::::::
:::::::::::::After reviewing your last postings info:
:::::::::::::My fustus “querstion” was if the radio operated in some degree of receiving stations ? via a tunable superheterodyne action / mode prior to the mass recapping of the unit ?
:::::::::::::
:::::::::::::
:::::::::::::
:::::::::::::Can we assume that C9..100 mmfd was ok and not even messed with ?
:::::::::::::Is cathode resistor R2 wired up ok and at its ~350 ohm value ?
:::::::::::::As well as the grid resistor of R1 ….50k wired properly and at its value ?
:::::::::::::The last item which I am sure that you did get involved with was the cathode bypass Condenser C7….05 ufd and it is OK and was reinstalled to the correct terminals…right…as that is also as critical as the 3 companion items.
:::::::::::::
:::::::::::::
:::::::::::::
:::::::::::::Looks as if the oscillator coil is on the larger ½ to ¾ in coil form and and a Litz wound unit in a tight layer…rather than the old style of enameled wire wound the full length of a long coil form. Plus, you seem to attest of its wirings continuity integrity as well as the adjunct tuning cap and its trimmer caps not being shorted out or dragging plates. Plus the additional reverting of one of the windings for a proper feed back phase check.
:::::::::::::Also with your BEE und KAY, you should be able to couple its input into the first grid of the mixer and at the proper injection of CW RF level, be able to swing its dial thru the 1005-2195 khc range and tune thru your stronger receptive stations in the area, with the two “TRF” stations being the powerhouses, BUT with the necessity of having to manually tune the tuning condenser in order to optimize the RF section being in resonance with them, when trying for weaker stations in bringing up received reception level..
:::::::::::::
:::::::::::::
:::::::::::::
:::::::::::::To further ease your mind about the radios oscillator sections L-C combinations , you could go to the juncture of C9 and R1 and couple in CW RF via a series / isolative ~100 pf cap and go to the same junction and tack on an anode of a 1N34 / 60 / 64 / 270 GERMANIUM diode and at its cathodes end , take a .001 cap for bypassing to ground and then meter the cathodes output via a VTVM.
:::::::::::::
:::::::::::::
:::::::::::::(N0…1N 914’s/4148’s/1N400oseries for this application)(Radio Shack stocks them in case you don’t have one from an oooold generation AM transistor radio chassis or from the building of a crystal set.)
:::::::::::::
:::::::::::::
:::::::::::::
:::::::::::::Then if you will power up the BEE und KAY and place in its CW mode and set the Emerson…(No power required....as this testing will be passive)…to the 1/3 lower end of the dial 700 kc ish (tuning cap ~ ¾ meshed)
:::::::::::::Then you tune the B & K in the ~1000-1400 range and see if the co-joined parasitic tuned oscillators circuit doesn’t give you a rising / declining reading as resonance was scanned across.
:::::::::::::Then, hop the radios tuning up to the higher third of the band (tuning cap ~ 1/4 meshed) and test for a like reading of a viable resonant circuit pair working at that
:::::::::::::frequency also.
:::::::::::::Thereby you have merely temp- rigged up a “po boys” grid dipper to interpret the presence of a functioning / resonating effect by the osc sections variable L-C pair and it having some degree of “Q”.
:::::::::::::
:::::::::::::
:::::::::::::The other alternative being that recurrent sweep Eico 460 Scope / Kluge of yours, so I think that with the former detected and metered RF , you would be much better off.
:::::::::::::
:::::::::::::
:::::::::::::
:::::::::::::Addenda:
:::::::::::::Noticed your new readings just at this posting time, and the bucolic local osc grid voltages reading. And have you confirmed that there is even any level oscillation by the taking of a portable xstr radios ferri-loop and placing it atop the osc coil winding and tune it off station just onto the very edge / sideband of a weaker ~1400-1740 kc AM station and then run the operating radio's tuning condenser across the bottom half of the AM band to see if even a weak heterodyning / birdie is heard on the xstr radio.
:::::::::::::
:::::::::::::Standing by for feed back
:::::::::::::
:::::::::::::
:::::::::::::73's de Edd
:::::::::::::
:::::::::::::
:::::::::::::
:::::::::::::
:::::::::::::
:::::::::::::
:::::::::::::
:::::::::::::
:::::::::::::
:::::::::::::
::::::::::::::Marv and all,
::::::::::::::
:::::::::::::: Here are the voltage readings on the 6A7 tube.
::::::::::::::
::::::::::::::Pins 1 & 7: 6.8 volts AC (Filament)
::::::::::::::Pin 2: 107.5 v DC (Plate)
::::::::::::::Pin 3: 43.5 volts DC (G3 and G5)
::::::::::::::Pin 4: 106.7 volts (G2)
::::::::::::::Pin 5: 2.2 V DC (G1)
::::::::::::::Pin 6: 2.647 volts DC (Cathode)
::::::::::::::Cap: -.361 v DC (G4)
::::::::::::::
::::::::::::::These seem like pretty healthy voltages to me. I don't see anything wrong there. The IF transformer is connecting B+ to the plate and the Oscillator coil is connecting B+ to to pin 4. So neither coil is open.
::::::::::::::
::::::::::::::I did notice that C17 was missing. I put it back and it might have made an improvement but not with the oscillator.
::::::::::::::
::::::::::::::Please if anyone has anymore ideas before I "attack" (very closely examine) the oscillator coil, please help.
::::::::::::::
::::::::::::::Thanks,
::::::::::::::
::::::::::::::Dave
::::::::::::::
:::::::::::::::Marv,
::::::::::::::: My RF signal generator modulates a 400 Hz tone on the 456 Kc carrier frequency when it's set to 456 Kc. The part of the radio that the signal generator is connected to is tune to exactly tuned to 456 Kc. It can receive 456 Kc and only 456 Kc. That "station" is received and I can blast the 400 Hz tone through the speaker of the radio. If I change the RF signal generator to another frequency, then no 400 Hz tone is heard. It is as perfectly aligned as I can get it. It may not have the best adjacent channel rejection but the signal is the strongest when the signal generator is set to 456 Kc.
::::::::::::::: The front part of the radio is what I'm having trouble with, and NOT the 456 Kc area. The radio is not converting (moving) the received frequency to 456 Kc. I can hear 570 Kc near the low end of the band and 620 Kc near the high end of the band (I live right near the brodcast antennas for these stations). That's all it does. It absolutely refuses to oscillate under any circumstances. I have checked about all I can check. All is working and not working at the same time.
::::::::::::::: The trimmers you are talking about are the oscillator trimmers that can only do anything, are only active, if the oscillator is working. I can put them in any position and they do nothing. They aren't shorted. They are perfectly good but not active because the oscillator is dead.
::::::::::::::: C-18 is brand new. It doesn't have any problems. One end is connected to the chassis and the other end is connected to a resistor. R3. I'll double check that it's also connected to the dead oscillator coil. It's not open. It just refuses to oscillate. All 11 paper and 2 electrolytic capacitors have been replaced. The positives of the electrolytic capacitors connect to the same place and the negatives connect to two different places.
::::::::::::::: I am getting close to removing the oscillator coil and replacing it or rewinding this one. If only I had the specs for this one. The part number on it is: 2DT200. Maybe someone has an Emerson specs book.
:::::::::::::::
:::::::::::::::Thanks,
:::::::::::::::
:::::::::::::::Dave
:::::::::::::::
::::::::::::::::Dave,
::::::::::::::::The oscillator has 2 trimmers in BC mode. One on the tuning cap (C-3) and the other at the rear (C-5), either of which could hamper operation if misadjusted. The one at C-3 is common to both SW and BC. Check C-18. Also, when you tested the IF, (456kHz) were you using signal levels low to moderate or high enough to blast through at any freq?
::::::::::::::::
::::::::::::::::marv
::::::::::::::::
:::::::::::::::::Marv,
::::::::::::::::: The resistors are the correct value. I checked them. I never replaced them. I also knew that the long black capacitor looking devices were also resistors. They are all correct. The capacitors are in the correct places. Nothing has been changed.
::::::::::::::::: I'll check the voltage and double check for "birdies". I think I did hear them. My huge isolation transformer is getting a lot of use on this restoration.
:::::::::::::::::
:::::::::::::::::Thanks,
:::::::::::::::::
:::::::::::::::::Dave
:::::::::::::::::
::::::::::::::::::Dave,
::::::::::::::::::In reading your 2 posts, I assume the set never worked and you re-capped and replaced bad resistors first. In this case, did you replace the parts just as they were originally installed, but did you also verify their placement via the schematic?
::::::::::::::::::
::::::::::::::::::marv
::::::::::::::::::
:::::::::::::::::::Radiodoc,
::::::::::::::::::: I just tried that and it makes absolutely no difference whatsoever.
::::::::::::::::::: What do I look at next?
:::::::::::::::::::
:::::::::::::::::::Thanks,
:::::::::::::::::::
::::::::::::::::::::Dave,
::::::::::::::::::::
::::::::::::::::::::The 98 volts is probably ok. If all else failed and as a shot in the dark, I would reverse the coil leads on the non-tuned winding between B+ and the oscillator "plate" and see what happens.
::::::::::::::::::::
::::::::::::::::::::Radiodoc
::::::::::::::::::::***************
::::::::::::::::::::
:::::::::::::::::::::Radiodoc,
::::::::::::::::::::: I took out the oscillator coil and checked every connection and all are good (Perfect), no opens. I checked and cleaned the band switch several times. I replaced C9 several times. When I connect 456 Kc to it from my RF signal generator, it receives that tone perfectly. It blasts!! But it wont take what's presented to it from the antenna terminals and convert that to 456 Kc. It absolutely refuses to do that under any circumstances.
::::::::::::::::::::: I checked all the connections and they are perfectly perfectly perfect. The resistors are all the correct values. The solder connections have been re-done and they are nice and shiny.
::::::::::::::::::::: I tried 3 different 6A7 tubes and none of them make any difference.
::::::::::::::::::::: I checked to make sure that the tuning capacitor or trimmer have any shorts on the oscillator side and there are no shorts. When the set is on and I try to adjust the oscillator screw or short the rotor with the stator on the oscillator side it makes no difference at all. All it's doing is "TRFing". The person who owns this radio MUST have the radio working immediately. I must continue working on it until it works. What do I do next? How do I convert it to a TRF receiver?
:::::::::::::::::::::
:::::::::::::::::::::Thanks,
:::::::::::::::::::::
:::::::::::::::::::::Dave
::::::::::::::::::::::Radiodoc,
:::::::::::::::::::::: B+ is 98 volts. Is that low? Shouldn't it be a little higher? I can't see any way to raise it. Filament voltage on the 6A7 is 5.3 volts.
::::::::::::::::::::::
::::::::::::::::::::::Thanks,
::::::::::::::::::::::
::::::::::::::::::::::Dave
:::::::::::::::::::::::Radiodoc,
::::::::::::::::::::::: C9 is a 100 pf capacitor. I replaced it and it made absolutely no difference.
:::::::::::::::::::::::
:::::::::::::::::::::::Dave
::::::::::::::::::::::::Dave,
::::::::::::::::::::::::
::::::::::::::::::::::::If all fails, walk away for a while and then come back and check carefully all the wiring around the osc circuit for correctness and good solder joints. Did you check C9 (probably a mica)or replace it. If not may try substituting another. Voltage checks on the stage may give a clue if any are off very much.
::::::::::::::::::::::::
::::::::::::::::::::::::Radiodoc
::::::::::::::::::::::::***********
::::::::::::::::::::::::
::::::::::::::::::::::::
:::::::::::::::::::::::::Hello All,
::::::::::::::::::::::::: I have checked everything and the oscillator absolutely refuses to work. All paper and filter capacitors have been replaced. No part of the oscillator coil is open. The resistors are good. I tried a few 6A7s and it still wont work. What to I look at next?
::::::::::::::::::::::::: This is an AC/DC set. There's not that much there.
:::::::::::::::::::::::::
:::::::::::::::::::::::::Thanks,
:::::::::::::::::::::::::
:::::::::::::::::::::::::Dave
Yes I did and the oscillator is still dead.
Thanks,
Dave
:Dave,
:I noted the cathode (self bias) resistor on the parts list is wire wound, which would make it inductive. Have you yet/or tried replacing it with a standard carbon resistor?
:
:marv
:
::Bill,
::
:: I replaced all the resistors and I still have a very dead oscillator.
::
::Dave
:::Dave, You didn't leave any of those old resistors in place? My next try...replace them all regardless of the readings.
:::Bill VA
:::
::::Bill,
:::: C8 is brand new. It is a bypass capacitor. The old waxy one was removed from the radio about a week ago. The circuit updates don't seem to have anything to do with the oscillator. The 456 Kc part of the radio works fine.
:::: When I attempted to look at C8, R9 (500K), in another part of the radio, fell apart. Also one of the leads fell off of a flexible resistor R2. So I had to replace them. I re-soldered the wire C8 wire to the 6A7 pin and it made absolutely no difference. The oscillator is still dead.
::::
:::: I do notice now that when the set is on a while, the B+ voltage goes down to 85 volts. These are brand new filter capacitors. So that cannot be the problem. I'll just have to replace every resistor, including the flexible ones. Those crimps onto the carbon must all be failing. I have tons of NOS old style resistors.
::::The Oscillator is still Dead Dead Dead.
:::: I'll replace the resistors and let everyone know if the oscillator starts to work. It will probably never work. I'll also try 7 or 8 more 6A7s.
:::: What should I look at next?
::::
::::Thanks,
::::
::::Dave
:::::Dave, I'm too slow (both ways) to keep up with this thread. But I got to wade in. C-8 is one to recheck, off the 6A7 screen. Also, just curious, did you need to make the changes to R-9, 11, & 12, and C-13 & 14 based on your serial number?
:::::
:::::Bill VA
:::::
:::::
::::::Radiodoc,
:::::: I just looked through the archives and found that if the voltage is positive it means that the oscillator is not operating. This is what I have been trying to tell you. The oscillator is dead. Ok, good, now we have absolute proof that the oscillator is dead. Now what do I look for? There could still be something not working. The oscillator coil? There is continuity but I don't know what it's value is in micro-henries. All I know is that it's a transformer. It has two primaries for the two bands, and one secondary. The part number on the oscillator coil 2DT200 matches the number in the service data. So it is original.
:::::: I'll keep checking the archives to see what others have done in this situation. I think that this may be a common problem. If you know what to check please let me know.
::::::
::::::Thanks,
::::::
::::::Dave
:::::::
:::::::Radiodoc,
::::::: Yes, it is positive. Pin 5 is 2.4 volts and pin 6 is 2.8 volts now. The only pins that are negative are the filament pins which are -23 volts DC with respect to the chassis. But they are 6.8 volts AC when I measure across the filament.
::::::: Is there something else wrong elsewhere in the set that's preventing the oscillator from working?
:::::::
:::::::Thanks,
:::::::
:::::::Dave
:::::::
::::::::Radiodoc,
:::::::: It was 2.2 volts and it wasn't minus. What would be wrong if it's positive?
:::::::: I'm going to double check that voltage.
::::::::
::::::::Thanks,
::::::::
::::::::Dave
:::::::::Dave,
:::::::::
:::::::::With the radio off did you try measuring between adjacent pins (with tube removed) to see if possibly there is an arc over between pins. You mentioned there was 2 volts on the oscillator grid. There should be a negative voltage on the oscillator grid unless you forgot to type a minus sign in front of the voltage reading you posted.
:::::::::
:::::::::Radiodoc
:::::::::************
:::::::::
::::::::::Marv,
:::::::::: The connections and the voltages are quite good. But it still wont oscillate. It works and absolutely refuses to work all at the same time.
::::::::::
::::::::::Thanks,
::::::::::
::::::::::Dave
:::::::::::Marv,
::::::::::: Yes they are. I measure the pin and the contact and I get the same reading from both. But I'll double check.
:::::::::::
:::::::::::Thanks,
:::::::::::
:::::::::::Dave
::::::::::::Dave,
::::::::::::You have eliminated almost everything. There is one remaining item though. Are you sure the socket/tube pin connections are firm?
::::::::::::
::::::::::::marv
::::::::::::
:::::::::::::Edd,
::::::::::::: This oscillator is dead, dead, dead. A transistor radio will pick up nothing from it. Also, the radio works exactly the same way whether the oscillator coil is connected to the oscillator side of the tuning capacitor or not. No difference. It absolutely refuses to oscillate even though all is connected perfectly. All components are good too (except for I believe, the oscillator coil). I have more than qadruple checked the 30K, 50K, and 300 whatever ohm resistors. They are hooked up correctly. Also, the another 100pf capacitor was tried and it makes no difference. It's still dead dead dead.
::::::::::::: I don't quite understand what you want me to do with the B & K. But I was able to use the B & K to "tune" the radio in the CW position. The rest of the radio receives the 460 Kc perfectly. So it's ready for the oscillator/mixer circuit to work. I am getting ready to replace the oscillator coil. I think I can take one from another AC/DC set just to try it out. Can I do that? I see the that there is a B+ side (output) and the other side that connects to the oscillator side of the tuning capacitor. I think that the second I replace the oscillator coil it will work perfectly. Please correct me if I'm wrong.
::::::::::::: The oscillator coil has two sections on it. One is the Litz wire and the other is the enameled wire.
::::::::::::: I think that what you want me to do at the junction of c1 and R9 is to inject an oscillation to see if I can then tune the radio normally with its tuning capacitor.
:::::::::::::
:::::::::::::Thanks,
:::::::::::::
:::::::::::::Dave
::::::::::::::
::::::::::::::
::::::::::::::
::::::::::::::
::::::::::::::After reviewing your last postings info:
::::::::::::::My fustus “querstion” was if the radio operated in some degree of receiving stations ? via a tunable superheterodyne action / mode prior to the mass recapping of the unit ?
::::::::::::::
::::::::::::::
::::::::::::::
::::::::::::::Can we assume that C9..100 mmfd was ok and not even messed with ?
::::::::::::::Is cathode resistor R2 wired up ok and at its ~350 ohm value ?
::::::::::::::As well as the grid resistor of R1 ….50k wired properly and at its value ?
::::::::::::::The last item which I am sure that you did get involved with was the cathode bypass Condenser C7….05 ufd and it is OK and was reinstalled to the correct terminals…right…as that is also as critical as the 3 companion items.
::::::::::::::
::::::::::::::
::::::::::::::
::::::::::::::Looks as if the oscillator coil is on the larger ½ to ¾ in coil form and and a Litz wound unit in a tight layer…rather than the old style of enameled wire wound the full length of a long coil form. Plus, you seem to attest of its wirings continuity integrity as well as the adjunct tuning cap and its trimmer caps not being shorted out or dragging plates. Plus the additional reverting of one of the windings for a proper feed back phase check.
::::::::::::::Also with your BEE und KAY, you should be able to couple its input into the first grid of the mixer and at the proper injection of CW RF level, be able to swing its dial thru the 1005-2195 khc range and tune thru your stronger receptive stations in the area, with the two “TRF” stations being the powerhouses, BUT with the necessity of having to manually tune the tuning condenser in order to optimize the RF section being in resonance with them, when trying for weaker stations in bringing up received reception level..
::::::::::::::
::::::::::::::
::::::::::::::
::::::::::::::To further ease your mind about the radios oscillator sections L-C combinations , you could go to the juncture of C9 and R1 and couple in CW RF via a series / isolative ~100 pf cap and go to the same junction and tack on an anode of a 1N34 / 60 / 64 / 270 GERMANIUM diode and at its cathodes end , take a .001 cap for bypassing to ground and then meter the cathodes output via a VTVM.
::::::::::::::
::::::::::::::
::::::::::::::(N0…1N 914’s/4148’s/1N400oseries for this application)(Radio Shack stocks them in case you don’t have one from an oooold generation AM transistor radio chassis or from the building of a crystal set.)
::::::::::::::
::::::::::::::
::::::::::::::
::::::::::::::Then if you will power up the BEE und KAY and place in its CW mode and set the Emerson…(No power required....as this testing will be passive)…to the 1/3 lower end of the dial 700 kc ish (tuning cap ~ ¾ meshed)
::::::::::::::Then you tune the B & K in the ~1000-1400 range and see if the co-joined parasitic tuned oscillators circuit doesn’t give you a rising / declining reading as resonance was scanned across.
::::::::::::::Then, hop the radios tuning up to the higher third of the band (tuning cap ~ 1/4 meshed) and test for a like reading of a viable resonant circuit pair working at that
::::::::::::::frequency also.
::::::::::::::Thereby you have merely temp- rigged up a “po boys” grid dipper to interpret the presence of a functioning / resonating effect by the osc sections variable L-C pair and it having some degree of “Q”.
::::::::::::::
::::::::::::::
::::::::::::::The other alternative being that recurrent sweep Eico 460 Scope / Kluge of yours, so I think that with the former detected and metered RF , you would be much better off.
::::::::::::::
::::::::::::::
::::::::::::::
::::::::::::::Addenda:
::::::::::::::Noticed your new readings just at this posting time, and the bucolic local osc grid voltages reading. And have you confirmed that there is even any level oscillation by the taking of a portable xstr radios ferri-loop and placing it atop the osc coil winding and tune it off station just onto the very edge / sideband of a weaker ~1400-1740 kc AM station and then run the operating radio's tuning condenser across the bottom half of the AM band to see if even a weak heterodyning / birdie is heard on the xstr radio.
::::::::::::::
::::::::::::::Standing by for feed back
::::::::::::::
::::::::::::::
::::::::::::::73's de Edd
::::::::::::::
::::::::::::::
::::::::::::::
::::::::::::::
::::::::::::::
::::::::::::::
::::::::::::::
::::::::::::::
::::::::::::::
::::::::::::::
:::::::::::::::Marv and all,
:::::::::::::::
::::::::::::::: Here are the voltage readings on the 6A7 tube.
:::::::::::::::
:::::::::::::::Pins 1 & 7: 6.8 volts AC (Filament)
:::::::::::::::Pin 2: 107.5 v DC (Plate)
:::::::::::::::Pin 3: 43.5 volts DC (G3 and G5)
:::::::::::::::Pin 4: 106.7 volts (G2)
:::::::::::::::Pin 5: 2.2 V DC (G1)
:::::::::::::::Pin 6: 2.647 volts DC (Cathode)
:::::::::::::::Cap: -.361 v DC (G4)
:::::::::::::::
:::::::::::::::These seem like pretty healthy voltages to me. I don't see anything wrong there. The IF transformer is connecting B+ to the plate and the Oscillator coil is connecting B+ to to pin 4. So neither coil is open.
:::::::::::::::
:::::::::::::::I did notice that C17 was missing. I put it back and it might have made an improvement but not with the oscillator.
:::::::::::::::
:::::::::::::::Please if anyone has anymore ideas before I "attack" (very closely examine) the oscillator coil, please help.
:::::::::::::::
:::::::::::::::Thanks,
:::::::::::::::
:::::::::::::::Dave
:::::::::::::::
::::::::::::::::Marv,
:::::::::::::::: My RF signal generator modulates a 400 Hz tone on the 456 Kc carrier frequency when it's set to 456 Kc. The part of the radio that the signal generator is connected to is tune to exactly tuned to 456 Kc. It can receive 456 Kc and only 456 Kc. That "station" is received and I can blast the 400 Hz tone through the speaker of the radio. If I change the RF signal generator to another frequency, then no 400 Hz tone is heard. It is as perfectly aligned as I can get it. It may not have the best adjacent channel rejection but the signal is the strongest when the signal generator is set to 456 Kc.
:::::::::::::::: The front part of the radio is what I'm having trouble with, and NOT the 456 Kc area. The radio is not converting (moving) the received frequency to 456 Kc. I can hear 570 Kc near the low end of the band and 620 Kc near the high end of the band (I live right near the brodcast antennas for these stations). That's all it does. It absolutely refuses to oscillate under any circumstances. I have checked about all I can check. All is working and not working at the same time.
:::::::::::::::: The trimmers you are talking about are the oscillator trimmers that can only do anything, are only active, if the oscillator is working. I can put them in any position and they do nothing. They aren't shorted. They are perfectly good but not active because the oscillator is dead.
:::::::::::::::: C-18 is brand new. It doesn't have any problems. One end is connected to the chassis and the other end is connected to a resistor. R3. I'll double check that it's also connected to the dead oscillator coil. It's not open. It just refuses to oscillate. All 11 paper and 2 electrolytic capacitors have been replaced. The positives of the electrolytic capacitors connect to the same place and the negatives connect to two different places.
:::::::::::::::: I am getting close to removing the oscillator coil and replacing it or rewinding this one. If only I had the specs for this one. The part number on it is: 2DT200. Maybe someone has an Emerson specs book.
::::::::::::::::
::::::::::::::::Thanks,
::::::::::::::::
::::::::::::::::Dave
::::::::::::::::
:::::::::::::::::Dave,
:::::::::::::::::The oscillator has 2 trimmers in BC mode. One on the tuning cap (C-3) and the other at the rear (C-5), either of which could hamper operation if misadjusted. The one at C-3 is common to both SW and BC. Check C-18. Also, when you tested the IF, (456kHz) were you using signal levels low to moderate or high enough to blast through at any freq?
:::::::::::::::::
:::::::::::::::::marv
:::::::::::::::::
::::::::::::::::::Marv,
:::::::::::::::::: The resistors are the correct value. I checked them. I never replaced them. I also knew that the long black capacitor looking devices were also resistors. They are all correct. The capacitors are in the correct places. Nothing has been changed.
:::::::::::::::::: I'll check the voltage and double check for "birdies". I think I did hear them. My huge isolation transformer is getting a lot of use on this restoration.
::::::::::::::::::
::::::::::::::::::Thanks,
::::::::::::::::::
::::::::::::::::::Dave
::::::::::::::::::
:::::::::::::::::::Dave,
:::::::::::::::::::In reading your 2 posts, I assume the set never worked and you re-capped and replaced bad resistors first. In this case, did you replace the parts just as they were originally installed, but did you also verify their placement via the schematic?
:::::::::::::::::::
:::::::::::::::::::marv
:::::::::::::::::::
::::::::::::::::::::Radiodoc,
:::::::::::::::::::: I just tried that and it makes absolutely no difference whatsoever.
:::::::::::::::::::: What do I look at next?
::::::::::::::::::::
::::::::::::::::::::Thanks,
::::::::::::::::::::
:::::::::::::::::::::Dave,
:::::::::::::::::::::
:::::::::::::::::::::The 98 volts is probably ok. If all else failed and as a shot in the dark, I would reverse the coil leads on the non-tuned winding between B+ and the oscillator "plate" and see what happens.
:::::::::::::::::::::
:::::::::::::::::::::Radiodoc
:::::::::::::::::::::***************
:::::::::::::::::::::
::::::::::::::::::::::Radiodoc,
:::::::::::::::::::::: I took out the oscillator coil and checked every connection and all are good (Perfect), no opens. I checked and cleaned the band switch several times. I replaced C9 several times. When I connect 456 Kc to it from my RF signal generator, it receives that tone perfectly. It blasts!! But it wont take what's presented to it from the antenna terminals and convert that to 456 Kc. It absolutely refuses to do that under any circumstances.
:::::::::::::::::::::: I checked all the connections and they are perfectly perfectly perfect. The resistors are all the correct values. The solder connections have been re-done and they are nice and shiny.
:::::::::::::::::::::: I tried 3 different 6A7 tubes and none of them make any difference.
:::::::::::::::::::::: I checked to make sure that the tuning capacitor or trimmer have any shorts on the oscillator side and there are no shorts. When the set is on and I try to adjust the oscillator screw or short the rotor with the stator on the oscillator side it makes no difference at all. All it's doing is "TRFing". The person who owns this radio MUST have the radio working immediately. I must continue working on it until it works. What do I do next? How do I convert it to a TRF receiver?
::::::::::::::::::::::
::::::::::::::::::::::Thanks,
::::::::::::::::::::::
::::::::::::::::::::::Dave
:::::::::::::::::::::::Radiodoc,
::::::::::::::::::::::: B+ is 98 volts. Is that low? Shouldn't it be a little higher? I can't see any way to raise it. Filament voltage on the 6A7 is 5.3 volts.
:::::::::::::::::::::::
:::::::::::::::::::::::Thanks,
:::::::::::::::::::::::
:::::::::::::::::::::::Dave
::::::::::::::::::::::::Radiodoc,
:::::::::::::::::::::::: C9 is a 100 pf capacitor. I replaced it and it made absolutely no difference.
::::::::::::::::::::::::
::::::::::::::::::::::::Dave
:::::::::::::::::::::::::Dave,
:::::::::::::::::::::::::
:::::::::::::::::::::::::If all fails, walk away for a while and then come back and check carefully all the wiring around the osc circuit for correctness and good solder joints. Did you check C9 (probably a mica)or replace it. If not may try substituting another. Voltage checks on the stage may give a clue if any are off very much.
:::::::::::::::::::::::::
:::::::::::::::::::::::::Radiodoc
:::::::::::::::::::::::::***********
:::::::::::::::::::::::::
:::::::::::::::::::::::::
::::::::::::::::::::::::::Hello All,
:::::::::::::::::::::::::: I have checked everything and the oscillator absolutely refuses to work. All paper and filter capacitors have been replaced. No part of the oscillator coil is open. The resistors are good. I tried a few 6A7s and it still wont work. What to I look at next?
:::::::::::::::::::::::::: This is an AC/DC set. There's not that much there.
::::::::::::::::::::::::::
::::::::::::::::::::::::::Thanks,
::::::::::::::::::::::::::
::::::::::::::::::::::::::Dave
How are you verifying osc operation DMM, VTVM, O'scope, looking for 456kHz at the 6A7 plate, looking for osc at the tank ckt, grids 1, 2, cathode? Keep in mind that even with a working oscillator, the lack of RF through that VERY UNUSUAL antenna transformer will not produce 456kHz. The tuning you described earlier from local stations at 570kHz on the low end tuning and 620kHz at the high end would suggest problems in the set's RF path or severe harmonic content from the station. If the detection was taking place in the audio stage(s), tuning should have no affect.
marv
:Bill,
: C8 is brand new. It is a bypass capacitor. The old waxy one was removed from the radio about a week ago. The circuit updates don't seem to have anything to do with the oscillator. The 456 Kc part of the radio works fine.
: When I attempted to look at C8, R9 (500K), in another part of the radio, fell apart. Also one of the leads fell off of a flexible resistor R2. So I had to replace them. I re-soldered the wire C8 wire to the 6A7 pin and it made absolutely no difference. The oscillator is still dead.
:
: I do notice now that when the set is on a while, the B+ voltage goes down to 85 volts. These are brand new filter capacitors. So that cannot be the problem. I'll just have to replace every resistor, including the flexible ones. Those crimps onto the carbon must all be failing. I have tons of NOS old style resistors.
:The Oscillator is still Dead Dead Dead.
: I'll replace the resistors and let everyone know if the oscillator starts to work. It will probably never work. I'll also try 7 or 8 more 6A7s.
: What should I look at next?
:
:Thanks,
:
:Dave
::Dave, I'm too slow (both ways) to keep up with this thread. But I got to wade in. C-8 is one to recheck, off the 6A7 screen. Also, just curious, did you need to make the changes to R-9, 11, & 12, and C-13 & 14 based on your serial number?
::
::Bill VA
::
::
:::Radiodoc,
::: I just looked through the archives and found that if the voltage is positive it means that the oscillator is not operating. This is what I have been trying to tell you. The oscillator is dead. Ok, good, now we have absolute proof that the oscillator is dead. Now what do I look for? There could still be something not working. The oscillator coil? There is continuity but I don't know what it's value is in micro-henries. All I know is that it's a transformer. It has two primaries for the two bands, and one secondary. The part number on the oscillator coil 2DT200 matches the number in the service data. So it is original.
::: I'll keep checking the archives to see what others have done in this situation. I think that this may be a common problem. If you know what to check please let me know.
:::
:::Thanks,
:::
:::Dave
::::
::::Radiodoc,
:::: Yes, it is positive. Pin 5 is 2.4 volts and pin 6 is 2.8 volts now. The only pins that are negative are the filament pins which are -23 volts DC with respect to the chassis. But they are 6.8 volts AC when I measure across the filament.
:::: Is there something else wrong elsewhere in the set that's preventing the oscillator from working?
::::
::::Thanks,
::::
::::Dave
::::
:::::Radiodoc,
::::: It was 2.2 volts and it wasn't minus. What would be wrong if it's positive?
::::: I'm going to double check that voltage.
:::::
:::::Thanks,
:::::
:::::Dave
::::::Dave,
::::::
::::::With the radio off did you try measuring between adjacent pins (with tube removed) to see if possibly there is an arc over between pins. You mentioned there was 2 volts on the oscillator grid. There should be a negative voltage on the oscillator grid unless you forgot to type a minus sign in front of the voltage reading you posted.
::::::
::::::Radiodoc
::::::************
::::::
:::::::Marv,
::::::: The connections and the voltages are quite good. But it still wont oscillate. It works and absolutely refuses to work all at the same time.
:::::::
:::::::Thanks,
:::::::
:::::::Dave
::::::::Marv,
:::::::: Yes they are. I measure the pin and the contact and I get the same reading from both. But I'll double check.
::::::::
::::::::Thanks,
::::::::
::::::::Dave
:::::::::Dave,
:::::::::You have eliminated almost everything. There is one remaining item though. Are you sure the socket/tube pin connections are firm?
:::::::::
:::::::::marv
:::::::::
::::::::::Edd,
:::::::::: This oscillator is dead, dead, dead. A transistor radio will pick up nothing from it. Also, the radio works exactly the same way whether the oscillator coil is connected to the oscillator side of the tuning capacitor or not. No difference. It absolutely refuses to oscillate even though all is connected perfectly. All components are good too (except for I believe, the oscillator coil). I have more than qadruple checked the 30K, 50K, and 300 whatever ohm resistors. They are hooked up correctly. Also, the another 100pf capacitor was tried and it makes no difference. It's still dead dead dead.
:::::::::: I don't quite understand what you want me to do with the B & K. But I was able to use the B & K to "tune" the radio in the CW position. The rest of the radio receives the 460 Kc perfectly. So it's ready for the oscillator/mixer circuit to work. I am getting ready to replace the oscillator coil. I think I can take one from another AC/DC set just to try it out. Can I do that? I see the that there is a B+ side (output) and the other side that connects to the oscillator side of the tuning capacitor. I think that the second I replace the oscillator coil it will work perfectly. Please correct me if I'm wrong.
:::::::::: The oscillator coil has two sections on it. One is the Litz wire and the other is the enameled wire.
:::::::::: I think that what you want me to do at the junction of c1 and R9 is to inject an oscillation to see if I can then tune the radio normally with its tuning capacitor.
::::::::::
::::::::::Thanks,
::::::::::
::::::::::Dave
:::::::::::
:::::::::::
:::::::::::
:::::::::::
:::::::::::After reviewing your last postings info:
:::::::::::My fustus “querstion” was if the radio operated in some degree of receiving stations ? via a tunable superheterodyne action / mode prior to the mass recapping of the unit ?
:::::::::::
:::::::::::
:::::::::::
:::::::::::Can we assume that C9..100 mmfd was ok and not even messed with ?
:::::::::::Is cathode resistor R2 wired up ok and at its ~350 ohm value ?
:::::::::::As well as the grid resistor of R1 ….50k wired properly and at its value ?
:::::::::::The last item which I am sure that you did get involved with was the cathode bypass Condenser C7….05 ufd and it is OK and was reinstalled to the correct terminals…right…as that is also as critical as the 3 companion items.
:::::::::::
:::::::::::
:::::::::::
:::::::::::Looks as if the oscillator coil is on the larger ½ to ¾ in coil form and and a Litz wound unit in a tight layer…rather than the old style of enameled wire wound the full length of a long coil form. Plus, you seem to attest of its wirings continuity integrity as well as the adjunct tuning cap and its trimmer caps not being shorted out or dragging plates. Plus the additional reverting of one of the windings for a proper feed back phase check.
:::::::::::Also with your BEE und KAY, you should be able to couple its input into the first grid of the mixer and at the proper injection of CW RF level, be able to swing its dial thru the 1005-2195 khc range and tune thru your stronger receptive stations in the area, with the two “TRF” stations being the powerhouses, BUT with the necessity of having to manually tune the tuning condenser in order to optimize the RF section being in resonance with them, when trying for weaker stations in bringing up received reception level..
:::::::::::
:::::::::::
:::::::::::
:::::::::::To further ease your mind about the radios oscillator sections L-C combinations , you could go to the juncture of C9 and R1 and couple in CW RF via a series / isolative ~100 pf cap and go to the same junction and tack on an anode of a 1N34 / 60 / 64 / 270 GERMANIUM diode and at its cathodes end , take a .001 cap for bypassing to ground and then meter the cathodes output via a VTVM.
:::::::::::
:::::::::::
:::::::::::(N0…1N 914’s/4148’s/1N400oseries for this application)(Radio Shack stocks them in case you don’t have one from an oooold generation AM transistor radio chassis or from the building of a crystal set.)
:::::::::::
:::::::::::
:::::::::::
:::::::::::Then if you will power up the BEE und KAY and place in its CW mode and set the Emerson…(No power required....as this testing will be passive)…to the 1/3 lower end of the dial 700 kc ish (tuning cap ~ ¾ meshed)
:::::::::::Then you tune the B & K in the ~1000-1400 range and see if the co-joined parasitic tuned oscillators circuit doesn’t give you a rising / declining reading as resonance was scanned across.
:::::::::::Then, hop the radios tuning up to the higher third of the band (tuning cap ~ 1/4 meshed) and test for a like reading of a viable resonant circuit pair working at that
:::::::::::frequency also.
:::::::::::Thereby you have merely temp- rigged up a “po boys” grid dipper to interpret the presence of a functioning / resonating effect by the osc sections variable L-C pair and it having some degree of “Q”.
:::::::::::
:::::::::::
:::::::::::The other alternative being that recurrent sweep Eico 460 Scope / Kluge of yours, so I think that with the former detected and metered RF , you would be much better off.
:::::::::::
:::::::::::
:::::::::::
:::::::::::Addenda:
:::::::::::Noticed your new readings just at this posting time, and the bucolic local osc grid voltages reading. And have you confirmed that there is even any level oscillation by the taking of a portable xstr radios ferri-loop and placing it atop the osc coil winding and tune it off station just onto the very edge / sideband of a weaker ~1400-1740 kc AM station and then run the operating radio's tuning condenser across the bottom half of the AM band to see if even a weak heterodyning / birdie is heard on the xstr radio.
:::::::::::
:::::::::::Standing by for feed back
:::::::::::
:::::::::::
:::::::::::73's de Edd
:::::::::::
:::::::::::
:::::::::::
:::::::::::
:::::::::::
:::::::::::
:::::::::::
:::::::::::
:::::::::::
:::::::::::
::::::::::::Marv and all,
::::::::::::
:::::::::::: Here are the voltage readings on the 6A7 tube.
::::::::::::
::::::::::::Pins 1 & 7: 6.8 volts AC (Filament)
::::::::::::Pin 2: 107.5 v DC (Plate)
::::::::::::Pin 3: 43.5 volts DC (G3 and G5)
::::::::::::Pin 4: 106.7 volts (G2)
::::::::::::Pin 5: 2.2 V DC (G1)
::::::::::::Pin 6: 2.647 volts DC (Cathode)
::::::::::::Cap: -.361 v DC (G4)
::::::::::::
::::::::::::These seem like pretty healthy voltages to me. I don't see anything wrong there. The IF transformer is connecting B+ to the plate and the Oscillator coil is connecting B+ to to pin 4. So neither coil is open.
::::::::::::
::::::::::::I did notice that C17 was missing. I put it back and it might have made an improvement but not with the oscillator.
::::::::::::
::::::::::::Please if anyone has anymore ideas before I "attack" (very closely examine) the oscillator coil, please help.
::::::::::::
::::::::::::Thanks,
::::::::::::
::::::::::::Dave
::::::::::::
:::::::::::::Marv,
::::::::::::: My RF signal generator modulates a 400 Hz tone on the 456 Kc carrier frequency when it's set to 456 Kc. The part of the radio that the signal generator is connected to is tune to exactly tuned to 456 Kc. It can receive 456 Kc and only 456 Kc. That "station" is received and I can blast the 400 Hz tone through the speaker of the radio. If I change the RF signal generator to another frequency, then no 400 Hz tone is heard. It is as perfectly aligned as I can get it. It may not have the best adjacent channel rejection but the signal is the strongest when the signal generator is set to 456 Kc.
::::::::::::: The front part of the radio is what I'm having trouble with, and NOT the 456 Kc area. The radio is not converting (moving) the received frequency to 456 Kc. I can hear 570 Kc near the low end of the band and 620 Kc near the high end of the band (I live right near the brodcast antennas for these stations). That's all it does. It absolutely refuses to oscillate under any circumstances. I have checked about all I can check. All is working and not working at the same time.
::::::::::::: The trimmers you are talking about are the oscillator trimmers that can only do anything, are only active, if the oscillator is working. I can put them in any position and they do nothing. They aren't shorted. They are perfectly good but not active because the oscillator is dead.
::::::::::::: C-18 is brand new. It doesn't have any problems. One end is connected to the chassis and the other end is connected to a resistor. R3. I'll double check that it's also connected to the dead oscillator coil. It's not open. It just refuses to oscillate. All 11 paper and 2 electrolytic capacitors have been replaced. The positives of the electrolytic capacitors connect to the same place and the negatives connect to two different places.
::::::::::::: I am getting close to removing the oscillator coil and replacing it or rewinding this one. If only I had the specs for this one. The part number on it is: 2DT200. Maybe someone has an Emerson specs book.
:::::::::::::
:::::::::::::Thanks,
:::::::::::::
:::::::::::::Dave
:::::::::::::
::::::::::::::Dave,
::::::::::::::The oscillator has 2 trimmers in BC mode. One on the tuning cap (C-3) and the other at the rear (C-5), either of which could hamper operation if misadjusted. The one at C-3 is common to both SW and BC. Check C-18. Also, when you tested the IF, (456kHz) were you using signal levels low to moderate or high enough to blast through at any freq?
::::::::::::::
::::::::::::::marv
::::::::::::::
:::::::::::::::Marv,
::::::::::::::: The resistors are the correct value. I checked them. I never replaced them. I also knew that the long black capacitor looking devices were also resistors. They are all correct. The capacitors are in the correct places. Nothing has been changed.
::::::::::::::: I'll check the voltage and double check for "birdies". I think I did hear them. My huge isolation transformer is getting a lot of use on this restoration.
:::::::::::::::
:::::::::::::::Thanks,
:::::::::::::::
:::::::::::::::Dave
:::::::::::::::
::::::::::::::::Dave,
::::::::::::::::In reading your 2 posts, I assume the set never worked and you re-capped and replaced bad resistors first. In this case, did you replace the parts just as they were originally installed, but did you also verify their placement via the schematic?
::::::::::::::::
::::::::::::::::marv
::::::::::::::::
:::::::::::::::::Radiodoc,
::::::::::::::::: I just tried that and it makes absolutely no difference whatsoever.
::::::::::::::::: What do I look at next?
:::::::::::::::::
:::::::::::::::::Thanks,
:::::::::::::::::
::::::::::::::::::Dave,
::::::::::::::::::
::::::::::::::::::The 98 volts is probably ok. If all else failed and as a shot in the dark, I would reverse the coil leads on the non-tuned winding between B+ and the oscillator "plate" and see what happens.
::::::::::::::::::
::::::::::::::::::Radiodoc
::::::::::::::::::***************
::::::::::::::::::
:::::::::::::::::::Radiodoc,
::::::::::::::::::: I took out the oscillator coil and checked every connection and all are good (Perfect), no opens. I checked and cleaned the band switch several times. I replaced C9 several times. When I connect 456 Kc to it from my RF signal generator, it receives that tone perfectly. It blasts!! But it wont take what's presented to it from the antenna terminals and convert that to 456 Kc. It absolutely refuses to do that under any circumstances.
::::::::::::::::::: I checked all the connections and they are perfectly perfectly perfect. The resistors are all the correct values. The solder connections have been re-done and they are nice and shiny.
::::::::::::::::::: I tried 3 different 6A7 tubes and none of them make any difference.
::::::::::::::::::: I checked to make sure that the tuning capacitor or trimmer have any shorts on the oscillator side and there are no shorts. When the set is on and I try to adjust the oscillator screw or short the rotor with the stator on the oscillator side it makes no difference at all. All it's doing is "TRFing". The person who owns this radio MUST have the radio working immediately. I must continue working on it until it works. What do I do next? How do I convert it to a TRF receiver?
:::::::::::::::::::
:::::::::::::::::::Thanks,
:::::::::::::::::::
:::::::::::::::::::Dave
::::::::::::::::::::Radiodoc,
:::::::::::::::::::: B+ is 98 volts. Is that low? Shouldn't it be a little higher? I can't see any way to raise it. Filament voltage on the 6A7 is 5.3 volts.
::::::::::::::::::::
::::::::::::::::::::Thanks,
::::::::::::::::::::
::::::::::::::::::::Dave
:::::::::::::::::::::Radiodoc,
::::::::::::::::::::: C9 is a 100 pf capacitor. I replaced it and it made absolutely no difference.
:::::::::::::::::::::
:::::::::::::::::::::Dave
::::::::::::::::::::::Dave,
::::::::::::::::::::::
::::::::::::::::::::::If all fails, walk away for a while and then come back and check carefully all the wiring around the osc circuit for correctness and good solder joints. Did you check C9 (probably a mica)or replace it. If not may try substituting another. Voltage checks on the stage may give a clue if any are off very much.
::::::::::::::::::::::
::::::::::::::::::::::Radiodoc
::::::::::::::::::::::***********
::::::::::::::::::::::
::::::::::::::::::::::
:::::::::::::::::::::::Hello All,
::::::::::::::::::::::: I have checked everything and the oscillator absolutely refuses to work. All paper and filter capacitors have been replaced. No part of the oscillator coil is open. The resistors are good. I tried a few 6A7s and it still wont work. What to I look at next?
::::::::::::::::::::::: This is an AC/DC set. There's not that much there.
:::::::::::::::::::::::
:::::::::::::::::::::::Thanks,
:::::::::::::::::::::::
:::::::::::::::::::::::Dave
I have the antenna wire connected to a very large antenna. I'll say it again. I receive 3 stations. The first station is at 570Kc, the second station is at 620Kc, and the third is at 1490Kc. As I turn past 620Kc, I continue to hear 620Kc all through the band but more faintly than I do at 620Kc. When I get to 1490Kc I can hear that station mixed with 620Kc. That's all it receives even if the oscillator coil is disconnected from the oscillator side of the tuning capacitor. The tuning capacitor works perfectly. There are no shorts between plates. The trimmer is fine too. The oscillator remains dead.
What do I look at next?
Thanks,
Dave
:Dave,
:How are you verifying osc operation DMM, VTVM, O'scope, looking for 456kHz at the 6A7 plate, looking for osc at the tank ckt, grids 1, 2, cathode? Keep in mind that even with a working oscillator, the lack of RF through that VERY UNUSUAL antenna transformer will not produce 456kHz. The tuning you described earlier from local stations at 570kHz on the low end tuning and 620kHz at the high end would suggest problems in the set's RF path or severe harmonic content from the station. If the detection was taking place in the audio stage(s), tuning should have no affect.
:
:marv
:
::Bill,
:: C8 is brand new. It is a bypass capacitor. The old waxy one was removed from the radio about a week ago. The circuit updates don't seem to have anything to do with the oscillator. The 456 Kc part of the radio works fine.
:: When I attempted to look at C8, R9 (500K), in another part of the radio, fell apart. Also one of the leads fell off of a flexible resistor R2. So I had to replace them. I re-soldered the wire C8 wire to the 6A7 pin and it made absolutely no difference. The oscillator is still dead.
::
:: I do notice now that when the set is on a while, the B+ voltage goes down to 85 volts. These are brand new filter capacitors. So that cannot be the problem. I'll just have to replace every resistor, including the flexible ones. Those crimps onto the carbon must all be failing. I have tons of NOS old style resistors.
::The Oscillator is still Dead Dead Dead.
:: I'll replace the resistors and let everyone know if the oscillator starts to work. It will probably never work. I'll also try 7 or 8 more 6A7s.
:: What should I look at next?
::
::Thanks,
::
::Dave
:::Dave, I'm too slow (both ways) to keep up with this thread. But I got to wade in. C-8 is one to recheck, off the 6A7 screen. Also, just curious, did you need to make the changes to R-9, 11, & 12, and C-13 & 14 based on your serial number?
:::
:::Bill VA
:::
:::
::::Radiodoc,
:::: I just looked through the archives and found that if the voltage is positive it means that the oscillator is not operating. This is what I have been trying to tell you. The oscillator is dead. Ok, good, now we have absolute proof that the oscillator is dead. Now what do I look for? There could still be something not working. The oscillator coil? There is continuity but I don't know what it's value is in micro-henries. All I know is that it's a transformer. It has two primaries for the two bands, and one secondary. The part number on the oscillator coil 2DT200 matches the number in the service data. So it is original.
:::: I'll keep checking the archives to see what others have done in this situation. I think that this may be a common problem. If you know what to check please let me know.
::::
::::Thanks,
::::
::::Dave
:::::
:::::Radiodoc,
::::: Yes, it is positive. Pin 5 is 2.4 volts and pin 6 is 2.8 volts now. The only pins that are negative are the filament pins which are -23 volts DC with respect to the chassis. But they are 6.8 volts AC when I measure across the filament.
::::: Is there something else wrong elsewhere in the set that's preventing the oscillator from working?
:::::
:::::Thanks,
:::::
:::::Dave
:::::
::::::Radiodoc,
:::::: It was 2.2 volts and it wasn't minus. What would be wrong if it's positive?
:::::: I'm going to double check that voltage.
::::::
::::::Thanks,
::::::
::::::Dave
:::::::Dave,
:::::::
:::::::With the radio off did you try measuring between adjacent pins (with tube removed) to see if possibly there is an arc over between pins. You mentioned there was 2 volts on the oscillator grid. There should be a negative voltage on the oscillator grid unless you forgot to type a minus sign in front of the voltage reading you posted.
:::::::
:::::::Radiodoc
:::::::************
:::::::
::::::::Marv,
:::::::: The connections and the voltages are quite good. But it still wont oscillate. It works and absolutely refuses to work all at the same time.
::::::::
::::::::Thanks,
::::::::
::::::::Dave
:::::::::Marv,
::::::::: Yes they are. I measure the pin and the contact and I get the same reading from both. But I'll double check.
:::::::::
:::::::::Thanks,
:::::::::
:::::::::Dave
::::::::::Dave,
::::::::::You have eliminated almost everything. There is one remaining item though. Are you sure the socket/tube pin connections are firm?
::::::::::
::::::::::marv
::::::::::
:::::::::::Edd,
::::::::::: This oscillator is dead, dead, dead. A transistor radio will pick up nothing from it. Also, the radio works exactly the same way whether the oscillator coil is connected to the oscillator side of the tuning capacitor or not. No difference. It absolutely refuses to oscillate even though all is connected perfectly. All components are good too (except for I believe, the oscillator coil). I have more than qadruple checked the 30K, 50K, and 300 whatever ohm resistors. They are hooked up correctly. Also, the another 100pf capacitor was tried and it makes no difference. It's still dead dead dead.
::::::::::: I don't quite understand what you want me to do with the B & K. But I was able to use the B & K to "tune" the radio in the CW position. The rest of the radio receives the 460 Kc perfectly. So it's ready for the oscillator/mixer circuit to work. I am getting ready to replace the oscillator coil. I think I can take one from another AC/DC set just to try it out. Can I do that? I see the that there is a B+ side (output) and the other side that connects to the oscillator side of the tuning capacitor. I think that the second I replace the oscillator coil it will work perfectly. Please correct me if I'm wrong.
::::::::::: The oscillator coil has two sections on it. One is the Litz wire and the other is the enameled wire.
::::::::::: I think that what you want me to do at the junction of c1 and R9 is to inject an oscillation to see if I can then tune the radio normally with its tuning capacitor.
:::::::::::
:::::::::::Thanks,
:::::::::::
:::::::::::Dave
::::::::::::
::::::::::::
::::::::::::
::::::::::::
::::::::::::After reviewing your last postings info:
::::::::::::My fustus “querstion” was if the radio operated in some degree of receiving stations ? via a tunable superheterodyne action / mode prior to the mass recapping of the unit ?
::::::::::::
::::::::::::
::::::::::::
::::::::::::Can we assume that C9..100 mmfd was ok and not even messed with ?
::::::::::::Is cathode resistor R2 wired up ok and at its ~350 ohm value ?
::::::::::::As well as the grid resistor of R1 ….50k wired properly and at its value ?
::::::::::::The last item which I am sure that you did get involved with was the cathode bypass Condenser C7….05 ufd and it is OK and was reinstalled to the correct terminals…right…as that is also as critical as the 3 companion items.
::::::::::::
::::::::::::
::::::::::::
::::::::::::Looks as if the oscillator coil is on the larger ½ to ¾ in coil form and and a Litz wound unit in a tight layer…rather than the old style of enameled wire wound the full length of a long coil form. Plus, you seem to attest of its wirings continuity integrity as well as the adjunct tuning cap and its trimmer caps not being shorted out or dragging plates. Plus the additional reverting of one of the windings for a proper feed back phase check.
::::::::::::Also with your BEE und KAY, you should be able to couple its input into the first grid of the mixer and at the proper injection of CW RF level, be able to swing its dial thru the 1005-2195 khc range and tune thru your stronger receptive stations in the area, with the two “TRF” stations being the powerhouses, BUT with the necessity of having to manually tune the tuning condenser in order to optimize the RF section being in resonance with them, when trying for weaker stations in bringing up received reception level..
::::::::::::
::::::::::::
::::::::::::
::::::::::::To further ease your mind about the radios oscillator sections L-C combinations , you could go to the juncture of C9 and R1 and couple in CW RF via a series / isolative ~100 pf cap and go to the same junction and tack on an anode of a 1N34 / 60 / 64 / 270 GERMANIUM diode and at its cathodes end , take a .001 cap for bypassing to ground and then meter the cathodes output via a VTVM.
::::::::::::
::::::::::::
::::::::::::(N0…1N 914’s/4148’s/1N400oseries for this application)(Radio Shack stocks them in case you don’t have one from an oooold generation AM transistor radio chassis or from the building of a crystal set.)
::::::::::::
::::::::::::
::::::::::::
::::::::::::Then if you will power up the BEE und KAY and place in its CW mode and set the Emerson…(No power required....as this testing will be passive)…to the 1/3 lower end of the dial 700 kc ish (tuning cap ~ ¾ meshed)
::::::::::::Then you tune the B & K in the ~1000-1400 range and see if the co-joined parasitic tuned oscillators circuit doesn’t give you a rising / declining reading as resonance was scanned across.
::::::::::::Then, hop the radios tuning up to the higher third of the band (tuning cap ~ 1/4 meshed) and test for a like reading of a viable resonant circuit pair working at that
::::::::::::frequency also.
::::::::::::Thereby you have merely temp- rigged up a “po boys” grid dipper to interpret the presence of a functioning / resonating effect by the osc sections variable L-C pair and it having some degree of “Q”.
::::::::::::
::::::::::::
::::::::::::The other alternative being that recurrent sweep Eico 460 Scope / Kluge of yours, so I think that with the former detected and metered RF , you would be much better off.
::::::::::::
::::::::::::
::::::::::::
::::::::::::Addenda:
::::::::::::Noticed your new readings just at this posting time, and the bucolic local osc grid voltages reading. And have you confirmed that there is even any level oscillation by the taking of a portable xstr radios ferri-loop and placing it atop the osc coil winding and tune it off station just onto the very edge / sideband of a weaker ~1400-1740 kc AM station and then run the operating radio's tuning condenser across the bottom half of the AM band to see if even a weak heterodyning / birdie is heard on the xstr radio.
::::::::::::
::::::::::::Standing by for feed back
::::::::::::
::::::::::::
::::::::::::73's de Edd
::::::::::::
::::::::::::
::::::::::::
::::::::::::
::::::::::::
::::::::::::
::::::::::::
::::::::::::
::::::::::::
::::::::::::
:::::::::::::Marv and all,
:::::::::::::
::::::::::::: Here are the voltage readings on the 6A7 tube.
:::::::::::::
:::::::::::::Pins 1 & 7: 6.8 volts AC (Filament)
:::::::::::::Pin 2: 107.5 v DC (Plate)
:::::::::::::Pin 3: 43.5 volts DC (G3 and G5)
:::::::::::::Pin 4: 106.7 volts (G2)
:::::::::::::Pin 5: 2.2 V DC (G1)
:::::::::::::Pin 6: 2.647 volts DC (Cathode)
:::::::::::::Cap: -.361 v DC (G4)
:::::::::::::
:::::::::::::These seem like pretty healthy voltages to me. I don't see anything wrong there. The IF transformer is connecting B+ to the plate and the Oscillator coil is connecting B+ to to pin 4. So neither coil is open.
:::::::::::::
:::::::::::::I did notice that C17 was missing. I put it back and it might have made an improvement but not with the oscillator.
:::::::::::::
:::::::::::::Please if anyone has anymore ideas before I "attack" (very closely examine) the oscillator coil, please help.
:::::::::::::
:::::::::::::Thanks,
:::::::::::::
:::::::::::::Dave
:::::::::::::
::::::::::::::Marv,
:::::::::::::: My RF signal generator modulates a 400 Hz tone on the 456 Kc carrier frequency when it's set to 456 Kc. The part of the radio that the signal generator is connected to is tune to exactly tuned to 456 Kc. It can receive 456 Kc and only 456 Kc. That "station" is received and I can blast the 400 Hz tone through the speaker of the radio. If I change the RF signal generator to another frequency, then no 400 Hz tone is heard. It is as perfectly aligned as I can get it. It may not have the best adjacent channel rejection but the signal is the strongest when the signal generator is set to 456 Kc.
:::::::::::::: The front part of the radio is what I'm having trouble with, and NOT the 456 Kc area. The radio is not converting (moving) the received frequency to 456 Kc. I can hear 570 Kc near the low end of the band and 620 Kc near the high end of the band (I live right near the brodcast antennas for these stations). That's all it does. It absolutely refuses to oscillate under any circumstances. I have checked about all I can check. All is working and not working at the same time.
:::::::::::::: The trimmers you are talking about are the oscillator trimmers that can only do anything, are only active, if the oscillator is working. I can put them in any position and they do nothing. They aren't shorted. They are perfectly good but not active because the oscillator is dead.
:::::::::::::: C-18 is brand new. It doesn't have any problems. One end is connected to the chassis and the other end is connected to a resistor. R3. I'll double check that it's also connected to the dead oscillator coil. It's not open. It just refuses to oscillate. All 11 paper and 2 electrolytic capacitors have been replaced. The positives of the electrolytic capacitors connect to the same place and the negatives connect to two different places.
:::::::::::::: I am getting close to removing the oscillator coil and replacing it or rewinding this one. If only I had the specs for this one. The part number on it is: 2DT200. Maybe someone has an Emerson specs book.
::::::::::::::
::::::::::::::Thanks,
::::::::::::::
::::::::::::::Dave
::::::::::::::
:::::::::::::::Dave,
:::::::::::::::The oscillator has 2 trimmers in BC mode. One on the tuning cap (C-3) and the other at the rear (C-5), either of which could hamper operation if misadjusted. The one at C-3 is common to both SW and BC. Check C-18. Also, when you tested the IF, (456kHz) were you using signal levels low to moderate or high enough to blast through at any freq?
:::::::::::::::
:::::::::::::::marv
:::::::::::::::
::::::::::::::::Marv,
:::::::::::::::: The resistors are the correct value. I checked them. I never replaced them. I also knew that the long black capacitor looking devices were also resistors. They are all correct. The capacitors are in the correct places. Nothing has been changed.
:::::::::::::::: I'll check the voltage and double check for "birdies". I think I did hear them. My huge isolation transformer is getting a lot of use on this restoration.
::::::::::::::::
::::::::::::::::Thanks,
::::::::::::::::
::::::::::::::::Dave
::::::::::::::::
:::::::::::::::::Dave,
:::::::::::::::::In reading your 2 posts, I assume the set never worked and you re-capped and replaced bad resistors first. In this case, did you replace the parts just as they were originally installed, but did you also verify their placement via the schematic?
:::::::::::::::::
:::::::::::::::::marv
:::::::::::::::::
::::::::::::::::::Radiodoc,
:::::::::::::::::: I just tried that and it makes absolutely no difference whatsoever.
:::::::::::::::::: What do I look at next?
::::::::::::::::::
::::::::::::::::::Thanks,
::::::::::::::::::
:::::::::::::::::::Dave,
:::::::::::::::::::
:::::::::::::::::::The 98 volts is probably ok. If all else failed and as a shot in the dark, I would reverse the coil leads on the non-tuned winding between B+ and the oscillator "plate" and see what happens.
:::::::::::::::::::
:::::::::::::::::::Radiodoc
:::::::::::::::::::***************
:::::::::::::::::::
::::::::::::::::::::Radiodoc,
:::::::::::::::::::: I took out the oscillator coil and checked every connection and all are good (Perfect), no opens. I checked and cleaned the band switch several times. I replaced C9 several times. When I connect 456 Kc to it from my RF signal generator, it receives that tone perfectly. It blasts!! But it wont take what's presented to it from the antenna terminals and convert that to 456 Kc. It absolutely refuses to do that under any circumstances.
:::::::::::::::::::: I checked all the connections and they are perfectly perfectly perfect. The resistors are all the correct values. The solder connections have been re-done and they are nice and shiny.
:::::::::::::::::::: I tried 3 different 6A7 tubes and none of them make any difference.
:::::::::::::::::::: I checked to make sure that the tuning capacitor or trimmer have any shorts on the oscillator side and there are no shorts. When the set is on and I try to adjust the oscillator screw or short the rotor with the stator on the oscillator side it makes no difference at all. All it's doing is "TRFing". The person who owns this radio MUST have the radio working immediately. I must continue working on it until it works. What do I do next? How do I convert it to a TRF receiver?
::::::::::::::::::::
::::::::::::::::::::Thanks,
::::::::::::::::::::
::::::::::::::::::::Dave
:::::::::::::::::::::Radiodoc,
::::::::::::::::::::: B+ is 98 volts. Is that low? Shouldn't it be a little higher? I can't see any way to raise it. Filament voltage on the 6A7 is 5.3 volts.
:::::::::::::::::::::
:::::::::::::::::::::Thanks,
:::::::::::::::::::::
:::::::::::::::::::::Dave
::::::::::::::::::::::Radiodoc,
:::::::::::::::::::::: C9 is a 100 pf capacitor. I replaced it and it made absolutely no difference.
::::::::::::::::::::::
::::::::::::::::::::::Dave
:::::::::::::::::::::::Dave,
:::::::::::::::::::::::
:::::::::::::::::::::::If all fails, walk away for a while and then come back and check carefully all the wiring around the osc circuit for correctness and good solder joints. Did you check C9 (probably a mica)or replace it. If not may try substituting another. Voltage checks on the stage may give a clue if any are off very much.
:::::::::::::::::::::::
:::::::::::::::::::::::Radiodoc
:::::::::::::::::::::::***********
:::::::::::::::::::::::
:::::::::::::::::::::::
::::::::::::::::::::::::Hello All,
:::::::::::::::::::::::: I have checked everything and the oscillator absolutely refuses to work. All paper and filter capacitors have been replaced. No part of the oscillator coil is open. The resistors are good. I tried a few 6A7s and it still wont work. What to I look at next?
:::::::::::::::::::::::: This is an AC/DC set. There's not that much there.
::::::::::::::::::::::::
::::::::::::::::::::::::Thanks,
::::::::::::::::::::::::
::::::::::::::::::::::::Dave
Well then, how about trying out this possibility..........
Heard that you COULD get the receiver to present a proper heterodyning receiving action when injecting in your B&K CW signal in place of the non existant local oscilators signal...so possibly an end result is getting even yet closer.
( After I hear back from you on the original osc circuits test above, I wish that you would have tried that technique of the B & K's injected CW signal and using the adjunct diode detector circuit to confirm the "health" of the 6 resonating components associated with the mixers BC band's osc circuitry. Using that manner, you can see the actual presence of a valid tunable circuit being connected as you take the generators variable CW freq on the BC band and tune up to........at its peak tuning..... and then as you then tune past its resonant frequency. )
A damped or ineffective oscillator resonating circuit will not produce that distinct tuning response swing.
73's de Edd
:Marv,
: I have the antenna wire connected to a very large antenna. I'll say it again. I receive 3 stations. The first station is at 570Kc, the second station is at 620Kc, and the third is at 1490Kc. As I turn past 620Kc, I continue to hear 620Kc all through the band but more faintly than I do at 620Kc. When I get to 1490Kc I can hear that station mixed with 620Kc. That's all it receives even if the oscillator coil is disconnected from the oscillator side of the tuning capacitor. The tuning capacitor works perfectly. There are no shorts between plates. The trimmer is fine too. The oscillator remains dead.
:
:What do I look at next?
:
:Thanks,
:
:Dave
::Dave,
::How are you verifying osc operation DMM, VTVM, O'scope, looking for 456kHz at the 6A7 plate, looking for osc at the tank ckt, grids 1, 2, cathode? Keep in mind that even with a working oscillator, the lack of RF through that VERY UNUSUAL antenna transformer will not produce 456kHz. The tuning you described earlier from local stations at 570kHz on the low end tuning and 620kHz at the high end would suggest problems in the set's RF path or severe harmonic content from the station. If the detection was taking place in the audio stage(s), tuning should have no affect.
::
::marv
::
:::Bill,
::: C8 is brand new. It is a bypass capacitor. The old waxy one was removed from the radio about a week ago. The circuit updates don't seem to have anything to do with the oscillator. The 456 Kc part of the radio works fine.
::: When I attempted to look at C8, R9 (500K), in another part of the radio, fell apart. Also one of the leads fell off of a flexible resistor R2. So I had to replace them. I re-soldered the wire C8 wire to the 6A7 pin and it made absolutely no difference. The oscillator is still dead.
:::
::: I do notice now that when the set is on a while, the B+ voltage goes down to 85 volts. These are brand new filter capacitors. So that cannot be the problem. I'll just have to replace every resistor, including the flexible ones. Those crimps onto the carbon must all be failing. I have tons of NOS old style resistors.
:::The Oscillator is still Dead Dead Dead.
::: I'll replace the resistors and let everyone know if the oscillator starts to work. It will probably never work. I'll also try 7 or 8 more 6A7s.
::: What should I look at next?
:::
:::Thanks,
:::
:::Dave
::::Dave, I'm too slow (both ways) to keep up with this thread. But I got to wade in. C-8 is one to recheck, off the 6A7 screen. Also, just curious, did you need to make the changes to R-9, 11, & 12, and C-13 & 14 based on your serial number?
::::
::::Bill VA
::::
::::
:::::Radiodoc,
::::: I just looked through the archives and found that if the voltage is positive it means that the oscillator is not operating. This is what I have been trying to tell you. The oscillator is dead. Ok, good, now we have absolute proof that the oscillator is dead. Now what do I look for? There could still be something not working. The oscillator coil? There is continuity but I don't know what it's value is in micro-henries. All I know is that it's a transformer. It has two primaries for the two bands, and one secondary. The part number on the oscillator coil 2DT200 matches the number in the service data. So it is original.
::::: I'll keep checking the archives to see what others have done in this situation. I think that this may be a common problem. If you know what to check please let me know.
:::::
:::::Thanks,
:::::
:::::Dave
::::::
::::::Radiodoc,
:::::: Yes, it is positive. Pin 5 is 2.4 volts and pin 6 is 2.8 volts now. The only pins that are negative are the filament pins which are -23 volts DC with respect to the chassis. But they are 6.8 volts AC when I measure across the filament.
:::::: Is there something else wrong elsewhere in the set that's preventing the oscillator from working?
::::::
::::::Thanks,
::::::
::::::Dave
::::::
:::::::Radiodoc,
::::::: It was 2.2 volts and it wasn't minus. What would be wrong if it's positive?
::::::: I'm going to double check that voltage.
:::::::
:::::::Thanks,
:::::::
:::::::Dave
::::::::Dave,
::::::::
::::::::With the radio off did you try measuring between adjacent pins (with tube removed) to see if possibly there is an arc over between pins. You mentioned there was 2 volts on the oscillator grid. There should be a negative voltage on the oscillator grid unless you forgot to type a minus sign in front of the voltage reading you posted.
::::::::
::::::::Radiodoc
::::::::************
::::::::
:::::::::Marv,
::::::::: The connections and the voltages are quite good. But it still wont oscillate. It works and absolutely refuses to work all at the same time.
:::::::::
:::::::::Thanks,
:::::::::
:::::::::Dave
::::::::::Marv,
:::::::::: Yes they are. I measure the pin and the contact and I get the same reading from both. But I'll double check.
::::::::::
::::::::::Thanks,
::::::::::
::::::::::Dave
:::::::::::Dave,
:::::::::::You have eliminated almost everything. There is one remaining item though. Are you sure the socket/tube pin connections are firm?
:::::::::::
:::::::::::marv
:::::::::::
::::::::::::Edd,
:::::::::::: This oscillator is dead, dead, dead. A transistor radio will pick up nothing from it. Also, the radio works exactly the same way whether the oscillator coil is connected to the oscillator side of the tuning capacitor or not. No difference. It absolutely refuses to oscillate even though all is connected perfectly. All components are good too (except for I believe, the oscillator coil). I have more than qadruple checked the 30K, 50K, and 300 whatever ohm resistors. They are hooked up correctly. Also, the another 100pf capacitor was tried and it makes no difference. It's still dead dead dead.
:::::::::::: I don't quite understand what you want me to do with the B & K. But I was able to use the B & K to "tune" the radio in the CW position. The rest of the radio receives the 460 Kc perfectly. So it's ready for the oscillator/mixer circuit to work. I am getting ready to replace the oscillator coil. I think I can take one from another AC/DC set just to try it out. Can I do that? I see the that there is a B+ side (output) and the other side that connects to the oscillator side of the tuning capacitor. I think that the second I replace the oscillator coil it will work perfectly. Please correct me if I'm wrong.
:::::::::::: The oscillator coil has two sections on it. One is the Litz wire and the other is the enameled wire.
:::::::::::: I think that what you want me to do at the junction of c1 and R9 is to inject an oscillation to see if I can then tune the radio normally with its tuning capacitor.
::::::::::::
::::::::::::Thanks,
::::::::::::
::::::::::::Dave
:::::::::::::
:::::::::::::
:::::::::::::
:::::::::::::
:::::::::::::After reviewing your last postings info:
:::::::::::::My fustus “querstion” was if the radio operated in some degree of receiving stations ? via a tunable superheterodyne action / mode prior to the mass recapping of the unit ?
:::::::::::::
:::::::::::::
:::::::::::::
:::::::::::::Can we assume that C9..100 mmfd was ok and not even messed with ?
:::::::::::::Is cathode resistor R2 wired up ok and at its ~350 ohm value ?
:::::::::::::As well as the grid resistor of R1 ….50k wired properly and at its value ?
:::::::::::::The last item which I am sure that you did get involved with was the cathode bypass Condenser C7….05 ufd and it is OK and was reinstalled to the correct terminals…right…as that is also as critical as the 3 companion items.
:::::::::::::
:::::::::::::
:::::::::::::
:::::::::::::Looks as if the oscillator coil is on the larger ½ to ¾ in coil form and and a Litz wound unit in a tight layer…rather than the old style of enameled wire wound the full length of a long coil form. Plus, you seem to attest of its wirings continuity integrity as well as the adjunct tuning cap and its trimmer caps not being shorted out or dragging plates. Plus the additional reverting of one of the windings for a proper feed back phase check.
:::::::::::::Also with your BEE und KAY, you should be able to couple its input into the first grid of the mixer and at the proper injection of CW RF level, be able to swing its dial thru the 1005-2195 khc range and tune thru your stronger receptive stations in the area, with the two “TRF” stations being the powerhouses, BUT with the necessity of having to manually tune the tuning condenser in order to optimize the RF section being in resonance with them, when trying for weaker stations in bringing up received reception level..
:::::::::::::
:::::::::::::
:::::::::::::
:::::::::::::To further ease your mind about the radios oscillator sections L-C combinations , you could go to the juncture of C9 and R1 and couple in CW RF via a series / isolative ~100 pf cap and go to the same junction and tack on an anode of a 1N34 / 60 / 64 / 270 GERMANIUM diode and at its cathodes end , take a .001 cap for bypassing to ground and then meter the cathodes output via a VTVM.
:::::::::::::
:::::::::::::
:::::::::::::(N0…1N 914’s/4148’s/1N400oseries for this application)(Radio Shack stocks them in case you don’t have one from an oooold generation AM transistor radio chassis or from the building of a crystal set.)
:::::::::::::
:::::::::::::
:::::::::::::
:::::::::::::Then if you will power up the BEE und KAY and place in its CW mode and set the Emerson…(No power required....as this testing will be passive)…to the 1/3 lower end of the dial 700 kc ish (tuning cap ~ ¾ meshed)
:::::::::::::Then you tune the B & K in the ~1000-1400 range and see if the co-joined parasitic tuned oscillators circuit doesn’t give you a rising / declining reading as resonance was scanned across.
:::::::::::::Then, hop the radios tuning up to the higher third of the band (tuning cap ~ 1/4 meshed) and test for a like reading of a viable resonant circuit pair working at that
:::::::::::::frequency also.
:::::::::::::Thereby you have merely temp- rigged up a “po boys” grid dipper to interpret the presence of a functioning / resonating effect by the osc sections variable L-C pair and it having some degree of “Q”.
:::::::::::::
:::::::::::::
:::::::::::::The other alternative being that recurrent sweep Eico 460 Scope / Kluge of yours, so I think that with the former detected and metered RF , you would be much better off.
:::::::::::::
:::::::::::::
:::::::::::::
:::::::::::::Addenda:
:::::::::::::Noticed your new readings just at this posting time, and the bucolic local osc grid voltages reading. And have you confirmed that there is even any level oscillation by the taking of a portable xstr radios ferri-loop and placing it atop the osc coil winding and tune it off station just onto the very edge / sideband of a weaker ~1400-1740 kc AM station and then run the operating radio's tuning condenser across the bottom half of the AM band to see if even a weak heterodyning / birdie is heard on the xstr radio.
:::::::::::::
:::::::::::::Standing by for feed back
:::::::::::::
:::::::::::::
:::::::::::::73's de Edd
:::::::::::::
:::::::::::::
:::::::::::::
:::::::::::::
:::::::::::::
:::::::::::::
:::::::::::::
:::::::::::::
:::::::::::::
:::::::::::::
::::::::::::::Marv and all,
::::::::::::::
:::::::::::::: Here are the voltage readings on the 6A7 tube.
::::::::::::::
::::::::::::::Pins 1 & 7: 6.8 volts AC (Filament)
::::::::::::::Pin 2: 107.5 v DC (Plate)
::::::::::::::Pin 3: 43.5 volts DC (G3 and G5)
::::::::::::::Pin 4: 106.7 volts (G2)
::::::::::::::Pin 5: 2.2 V DC (G1)
::::::::::::::Pin 6: 2.647 volts DC (Cathode)
::::::::::::::Cap: -.361 v DC (G4)
::::::::::::::
::::::::::::::These seem like pretty healthy voltages to me. I don't see anything wrong there. The IF transformer is connecting B+ to the plate and the Oscillator coil is connecting B+ to to pin 4. So neither coil is open.
::::::::::::::
::::::::::::::I did notice that C17 was missing. I put it back and it might have made an improvement but not with the oscillator.
::::::::::::::
::::::::::::::Please if anyone has anymore ideas before I "attack" (very closely examine) the oscillator coil, please help.
::::::::::::::
::::::::::::::Thanks,
::::::::::::::
::::::::::::::Dave
::::::::::::::
:::::::::::::::Marv,
::::::::::::::: My RF signal generator modulates a 400 Hz tone on the 456 Kc carrier frequency when it's set to 456 Kc. The part of the radio that the signal generator is connected to is tune to exactly tuned to 456 Kc. It can receive 456 Kc and only 456 Kc. That "station" is received and I can blast the 400 Hz tone through the speaker of the radio. If I change the RF signal generator to another frequency, then no 400 Hz tone is heard. It is as perfectly aligned as I can get it. It may not have the best adjacent channel rejection but the signal is the strongest when the signal generator is set to 456 Kc.
::::::::::::::: The front part of the radio is what I'm having trouble with, and NOT the 456 Kc area. The radio is not converting (moving) the received frequency to 456 Kc. I can hear 570 Kc near the low end of the band and 620 Kc near the high end of the band (I live right near the brodcast antennas for these stations). That's all it does. It absolutely refuses to oscillate under any circumstances. I have checked about all I can check. All is working and not working at the same time.
::::::::::::::: The trimmers you are talking about are the oscillator trimmers that can only do anything, are only active, if the oscillator is working. I can put them in any position and they do nothing. They aren't shorted. They are perfectly good but not active because the oscillator is dead.
::::::::::::::: C-18 is brand new. It doesn't have any problems. One end is connected to the chassis and the other end is connected to a resistor. R3. I'll double check that it's also connected to the dead oscillator coil. It's not open. It just refuses to oscillate. All 11 paper and 2 electrolytic capacitors have been replaced. The positives of the electrolytic capacitors connect to the same place and the negatives connect to two different places.
::::::::::::::: I am getting close to removing the oscillator coil and replacing it or rewinding this one. If only I had the specs for this one. The part number on it is: 2DT200. Maybe someone has an Emerson specs book.
:::::::::::::::
:::::::::::::::Thanks,
:::::::::::::::
:::::::::::::::Dave
:::::::::::::::
::::::::::::::::Dave,
::::::::::::::::The oscillator has 2 trimmers in BC mode. One on the tuning cap (C-3) and the other at the rear (C-5), either of which could hamper operation if misadjusted. The one at C-3 is common to both SW and BC. Check C-18. Also, when you tested the IF, (456kHz) were you using signal levels low to moderate or high enough to blast through at any freq?
::::::::::::::::
::::::::::::::::marv
::::::::::::::::
:::::::::::::::::Marv,
::::::::::::::::: The resistors are the correct value. I checked them. I never replaced them. I also knew that the long black capacitor looking devices were also resistors. They are all correct. The capacitors are in the correct places. Nothing has been changed.
::::::::::::::::: I'll check the voltage and double check for "birdies". I think I did hear them. My huge isolation transformer is getting a lot of use on this restoration.
:::::::::::::::::
:::::::::::::::::Thanks,
:::::::::::::::::
:::::::::::::::::Dave
:::::::::::::::::
::::::::::::::::::Dave,
::::::::::::::::::In reading your 2 posts, I assume the set never worked and you re-capped and replaced bad resistors first. In this case, did you replace the parts just as they were originally installed, but did you also verify their placement via the schematic?
::::::::::::::::::
::::::::::::::::::marv
::::::::::::::::::
:::::::::::::::::::Radiodoc,
::::::::::::::::::: I just tried that and it makes absolutely no difference whatsoever.
::::::::::::::::::: What do I look at next?
:::::::::::::::::::
:::::::::::::::::::Thanks,
:::::::::::::::::::
::::::::::::::::::::Dave,
::::::::::::::::::::
::::::::::::::::::::The 98 volts is probably ok. If all else failed and as a shot in the dark, I would reverse the coil leads on the non-tuned winding between B+ and the oscillator "plate" and see what happens.
::::::::::::::::::::
::::::::::::::::::::Radiodoc
::::::::::::::::::::***************
::::::::::::::::::::
:::::::::::::::::::::Radiodoc,
::::::::::::::::::::: I took out the oscillator coil and checked every connection and all are good (Perfect), no opens. I checked and cleaned the band switch several times. I replaced C9 several times. When I connect 456 Kc to it from my RF signal generator, it receives that tone perfectly. It blasts!! But it wont take what's presented to it from the antenna terminals and convert that to 456 Kc. It absolutely refuses to do that under any circumstances.
::::::::::::::::::::: I checked all the connections and they are perfectly perfectly perfect. The resistors are all the correct values. The solder connections have been re-done and they are nice and shiny.
::::::::::::::::::::: I tried 3 different 6A7 tubes and none of them make any difference.
::::::::::::::::::::: I checked to make sure that the tuning capacitor or trimmer have any shorts on the oscillator side and there are no shorts. When the set is on and I try to adjust the oscillator screw or short the rotor with the stator on the oscillator side it makes no difference at all. All it's doing is "TRFing". The person who owns this radio MUST have the radio working immediately. I must continue working on it until it works. What do I do next? How do I convert it to a TRF receiver?
:::::::::::::::::::::
:::::::::::::::::::::Thanks,
:::::::::::::::::::::
:::::::::::::::::::::Dave
::::::::::::::::::::::Radiodoc,
:::::::::::::::::::::: B+ is 98 volts. Is that low? Shouldn't it be a little higher? I can't see any way to raise it. Filament voltage on the 6A7 is 5.3 volts.
::::::::::::::::::::::
::::::::::::::::::::::Thanks,
::::::::::::::::::::::
::::::::::::::::::::::Dave
:::::::::::::::::::::::Radiodoc,
::::::::::::::::::::::: C9 is a 100 pf capacitor. I replaced it and it made absolutely no difference.
:::::::::::::::::::::::
:::::::::::::::::::::::Dave
::::::::::::::::::::::::Dave,
::::::::::::::::::::::::
::::::::::::::::::::::::If all fails, walk away for a while and then come back and check carefully all the wiring around the osc circuit for correctness and good solder joints. Did you check C9 (probably a mica)or replace it. If not may try substituting another. Voltage checks on the stage may give a clue if any are off very much.
::::::::::::::::::::::::
::::::::::::::::::::::::Radiodoc
::::::::::::::::::::::::***********
::::::::::::::::::::::::
::::::::::::::::::::::::
:::::::::::::::::::::::::Hello All,
::::::::::::::::::::::::: I have checked everything and the oscillator absolutely refuses to work. All paper and filter capacitors have been replaced. No part of the oscillator coil is open. The resistors are good. I tried a few 6A7s and it still wont work. What to I look at next?
::::::::::::::::::::::::: This is an AC/DC set. There's not that much there.
:::::::::::::::::::::::::
:::::::::::::::::::::::::Thanks,
:::::::::::::::::::::::::
:::::::::::::::::::::::::Dave
I still don't understand how to hook this up and to what pins. I have a 1N914 diode.
Thanks,
Dave
This is Edd's picture found elsewhere. I hope it's ok here.
:
:
:
:
:
:Well then, how about trying out this possibility..........
:
:
:
:
:Heard that you COULD get the receiver to present a proper heterodyning receiving action when injecting in your B&K CW signal in place of the non existant local oscilators signal...so possibly an end result is getting even yet closer.
:
:( After I hear back from you on the original osc circuits test above, I wish that you would have tried that technique of the B & K's injected CW signal and using the adjunct diode detector circuit to confirm the "health" of the 6 resonating components associated with the mixers BC band's osc circuitry. Using that manner, you can see the actual presence of a valid tunable circuit being connected as you take the generators variable CW freq on the BC band and tune up to........at its peak tuning..... and then as you then tune past its resonant frequency. )
:
:
:A damped or ineffective oscillator resonating circuit will not produce that distinct tuning response swing.
:
:
:
:73's de Edd
:
:
:
:
:
:
:
:
::Marv,
:: I have the antenna wire connected to a very large antenna. I'll say it again. I receive 3 stations. The first station is at 570Kc, the second station is at 620Kc, and the third is at 1490Kc. As I turn past 620Kc, I continue to hear 620Kc all through the band but more faintly than I do at 620Kc. When I get to 1490Kc I can hear that station mixed with 620Kc. That's all it receives even if the oscillator coil is disconnected from the oscillator side of the tuning capacitor. The tuning capacitor works perfectly. There are no shorts between plates. The trimmer is fine too. The oscillator remains dead.
::
::What do I look at next?
::
::Thanks,
::
::Dave
:::Dave,
:::How are you verifying osc operation DMM, VTVM, O'scope, looking for 456kHz at the 6A7 plate, looking for osc at the tank ckt, grids 1, 2, cathode? Keep in mind that even with a working oscillator, the lack of RF through that VERY UNUSUAL antenna transformer will not produce 456kHz. The tuning you described earlier from local stations at 570kHz on the low end tuning and 620kHz at the high end would suggest problems in the set's RF path or severe harmonic content from the station. If the detection was taking place in the audio stage(s), tuning should have no affect.
:::
:::marv
:::
::::Bill,
:::: C8 is brand new. It is a bypass capacitor. The old waxy one was removed from the radio about a week ago. The circuit updates don't seem to have anything to do with the oscillator. The 456 Kc part of the radio works fine.
:::: When I attempted to look at C8, R9 (500K), in another part of the radio, fell apart. Also one of the leads fell off of a flexible resistor R2. So I had to replace them. I re-soldered the wire C8 wire to the 6A7 pin and it made absolutely no difference. The oscillator is still dead.
::::
:::: I do notice now that when the set is on a while, the B+ voltage goes down to 85 volts. These are brand new filter capacitors. So that cannot be the problem. I'll just have to replace every resistor, including the flexible ones. Those crimps onto the carbon must all be failing. I have tons of NOS old style resistors.
::::The Oscillator is still Dead Dead Dead.
:::: I'll replace the resistors and let everyone know if the oscillator starts to work. It will probably never work. I'll also try 7 or 8 more 6A7s.
:::: What should I look at next?
::::
::::Thanks,
::::
::::Dave
:::::Dave, I'm too slow (both ways) to keep up with this thread. But I got to wade in. C-8 is one to recheck, off the 6A7 screen. Also, just curious, did you need to make the changes to R-9, 11, & 12, and C-13 & 14 based on your serial number?
:::::
:::::Bill VA
:::::
:::::
::::::Radiodoc,
:::::: I just looked through the archives and found that if the voltage is positive it means that the oscillator is not operating. This is what I have been trying to tell you. The oscillator is dead. Ok, good, now we have absolute proof that the oscillator is dead. Now what do I look for? There could still be something not working. The oscillator coil? There is continuity but I don't know what it's value is in micro-henries. All I know is that it's a transformer. It has two primaries for the two bands, and one secondary. The part number on the oscillator coil 2DT200 matches the number in the service data. So it is original.
:::::: I'll keep checking the archives to see what others have done in this situation. I think that this may be a common problem. If you know what to check please let me know.
::::::
::::::Thanks,
::::::
::::::Dave
:::::::
:::::::Radiodoc,
::::::: Yes, it is positive. Pin 5 is 2.4 volts and pin 6 is 2.8 volts now. The only pins that are negative are the filament pins which are -23 volts DC with respect to the chassis. But they are 6.8 volts AC when I measure across the filament.
::::::: Is there something else wrong elsewhere in the set that's preventing the oscillator from working?
:::::::
:::::::Thanks,
:::::::
:::::::Dave
:::::::
::::::::Radiodoc,
:::::::: It was 2.2 volts and it wasn't minus. What would be wrong if it's positive?
:::::::: I'm going to double check that voltage.
::::::::
::::::::Thanks,
::::::::
::::::::Dave
:::::::::Dave,
:::::::::
:::::::::With the radio off did you try measuring between adjacent pins (with tube removed) to see if possibly there is an arc over between pins. You mentioned there was 2 volts on the oscillator grid. There should be a negative voltage on the oscillator grid unless you forgot to type a minus sign in front of the voltage reading you posted.
:::::::::
:::::::::Radiodoc
:::::::::************
:::::::::
::::::::::Marv,
:::::::::: The connections and the voltages are quite good. But it still wont oscillate. It works and absolutely refuses to work all at the same time.
::::::::::
::::::::::Thanks,
::::::::::
::::::::::Dave
:::::::::::Marv,
::::::::::: Yes they are. I measure the pin and the contact and I get the same reading from both. But I'll double check.
:::::::::::
:::::::::::Thanks,
:::::::::::
:::::::::::Dave
::::::::::::Dave,
::::::::::::You have eliminated almost everything. There is one remaining item though. Are you sure the socket/tube pin connections are firm?
::::::::::::
::::::::::::marv
::::::::::::
:::::::::::::Edd,
::::::::::::: This oscillator is dead, dead, dead. A transistor radio will pick up nothing from it. Also, the radio works exactly the same way whether the oscillator coil is connected to the oscillator side of the tuning capacitor or not. No difference. It absolutely refuses to oscillate even though all is connected perfectly. All components are good too (except for I believe, the oscillator coil). I have more than qadruple checked the 30K, 50K, and 300 whatever ohm resistors. They are hooked up correctly. Also, the another 100pf capacitor was tried and it makes no difference. It's still dead dead dead.
::::::::::::: I don't quite understand what you want me to do with the B & K. But I was able to use the B & K to "tune" the radio in the CW position. The rest of the radio receives the 460 Kc perfectly. So it's ready for the oscillator/mixer circuit to work. I am getting ready to replace the oscillator coil. I think I can take one from another AC/DC set just to try it out. Can I do that? I see the that there is a B+ side (output) and the other side that connects to the oscillator side of the tuning capacitor. I think that the second I replace the oscillator coil it will work perfectly. Please correct me if I'm wrong.
::::::::::::: The oscillator coil has two sections on it. One is the Litz wire and the other is the enameled wire.
::::::::::::: I think that what you want me to do at the junction of c1 and R9 is to inject an oscillation to see if I can then tune the radio normally with its tuning capacitor.
:::::::::::::
:::::::::::::Thanks,
:::::::::::::
:::::::::::::Dave
::::::::::::::
::::::::::::::
::::::::::::::
::::::::::::::
::::::::::::::After reviewing your last postings info:
::::::::::::::My fustus “querstion” was if the radio operated in some degree of receiving stations ? via a tunable superheterodyne action / mode prior to the mass recapping of the unit ?
::::::::::::::
::::::::::::::
::::::::::::::
::::::::::::::Can we assume that C9..100 mmfd was ok and not even messed with ?
::::::::::::::Is cathode resistor R2 wired up ok and at its ~350 ohm value ?
::::::::::::::As well as the grid resistor of R1 ….50k wired properly and at its value ?
::::::::::::::The last item which I am sure that you did get involved with was the cathode bypass Condenser C7….05 ufd and it is OK and was reinstalled to the correct terminals…right…as that is also as critical as the 3 companion items.
::::::::::::::
::::::::::::::
::::::::::::::
::::::::::::::Looks as if the oscillator coil is on the larger ½ to ¾ in coil form and and a Litz wound unit in a tight layer…rather than the old style of enameled wire wound the full length of a long coil form. Plus, you seem to attest of its wirings continuity integrity as well as the adjunct tuning cap and its trimmer caps not being shorted out or dragging plates. Plus the additional reverting of one of the windings for a proper feed back phase check.
::::::::::::::Also with your BEE und KAY, you should be able to couple its input into the first grid of the mixer and at the proper injection of CW RF level, be able to swing its dial thru the 1005-2195 khc range and tune thru your stronger receptive stations in the area, with the two “TRF” stations being the powerhouses, BUT with the necessity of having to manually tune the tuning condenser in order to optimize the RF section being in resonance with them, when trying for weaker stations in bringing up received reception level..
::::::::::::::
::::::::::::::
::::::::::::::
::::::::::::::To further ease your mind about the radios oscillator sections L-C combinations , you could go to the juncture of C9 and R1 and couple in CW RF via a series / isolative ~100 pf cap and go to the same junction and tack on an anode of a 1N34 / 60 / 64 / 270 GERMANIUM diode and at its cathodes end , take a .001 cap for bypassing to ground and then meter the cathodes output via a VTVM.
::::::::::::::
::::::::::::::
::::::::::::::(N0…1N 914’s/4148’s/1N400oseries for this application)(Radio Shack stocks them in case you don’t have one from an oooold generation AM transistor radio chassis or from the building of a crystal set.)
::::::::::::::
::::::::::::::
::::::::::::::
::::::::::::::Then if you will power up the BEE und KAY and place in its CW mode and set the Emerson…(No power required....as this testing will be passive)…to the 1/3 lower end of the dial 700 kc ish (tuning cap ~ ¾ meshed)
::::::::::::::Then you tune the B & K in the ~1000-1400 range and see if the co-joined parasitic tuned oscillators circuit doesn’t give you a rising / declining reading as resonance was scanned across.
::::::::::::::Then, hop the radios tuning up to the higher third of the band (tuning cap ~ 1/4 meshed) and test for a like reading of a viable resonant circuit pair working at that
::::::::::::::frequency also.
::::::::::::::Thereby you have merely temp- rigged up a “po boys” grid dipper to interpret the presence of a functioning / resonating effect by the osc sections variable L-C pair and it having some degree of “Q”.
::::::::::::::
::::::::::::::
::::::::::::::The other alternative being that recurrent sweep Eico 460 Scope / Kluge of yours, so I think that with the former detected and metered RF , you would be much better off.
::::::::::::::
::::::::::::::
::::::::::::::
::::::::::::::Addenda:
::::::::::::::Noticed your new readings just at this posting time, and the bucolic local osc grid voltages reading. And have you confirmed that there is even any level oscillation by the taking of a portable xstr radios ferri-loop and placing it atop the osc coil winding and tune it off station just onto the very edge / sideband of a weaker ~1400-1740 kc AM station and then run the operating radio's tuning condenser across the bottom half of the AM band to see if even a weak heterodyning / birdie is heard on the xstr radio.
::::::::::::::
::::::::::::::Standing by for feed back
::::::::::::::
::::::::::::::
::::::::::::::73's de Edd
::::::::::::::
::::::::::::::
::::::::::::::
::::::::::::::
::::::::::::::
::::::::::::::
::::::::::::::
::::::::::::::
::::::::::::::
::::::::::::::
:::::::::::::::Marv and all,
:::::::::::::::
::::::::::::::: Here are the voltage readings on the 6A7 tube.
:::::::::::::::
:::::::::::::::Pins 1 & 7: 6.8 volts AC (Filament)
:::::::::::::::Pin 2: 107.5 v DC (Plate)
:::::::::::::::Pin 3: 43.5 volts DC (G3 and G5)
:::::::::::::::Pin 4: 106.7 volts (G2)
:::::::::::::::Pin 5: 2.2 V DC (G1)
:::::::::::::::Pin 6: 2.647 volts DC (Cathode)
:::::::::::::::Cap: -.361 v DC (G4)
:::::::::::::::
:::::::::::::::These seem like pretty healthy voltages to me. I don't see anything wrong there. The IF transformer is connecting B+ to the plate and the Oscillator coil is connecting B+ to to pin 4. So neither coil is open.
:::::::::::::::
:::::::::::::::I did notice that C17 was missing. I put it back and it might have made an improvement but not with the oscillator.
:::::::::::::::
:::::::::::::::Please if anyone has anymore ideas before I "attack" (very closely examine) the oscillator coil, please help.
:::::::::::::::
:::::::::::::::Thanks,
:::::::::::::::
:::::::::::::::Dave
:::::::::::::::
::::::::::::::::Marv,
:::::::::::::::: My RF signal generator modulates a 400 Hz tone on the 456 Kc carrier frequency when it's set to 456 Kc. The part of the radio that the signal generator is connected to is tune to exactly tuned to 456 Kc. It can receive 456 Kc and only 456 Kc. That "station" is received and I can blast the 400 Hz tone through the speaker of the radio. If I change the RF signal generator to another frequency, then no 400 Hz tone is heard. It is as perfectly aligned as I can get it. It may not have the best adjacent channel rejection but the signal is the strongest when the signal generator is set to 456 Kc.
:::::::::::::::: The front part of the radio is what I'm having trouble with, and NOT the 456 Kc area. The radio is not converting (moving) the received frequency to 456 Kc. I can hear 570 Kc near the low end of the band and 620 Kc near the high end of the band (I live right near the brodcast antennas for these stations). That's all it does. It absolutely refuses to oscillate under any circumstances. I have checked about all I can check. All is working and not working at the same time.
:::::::::::::::: The trimmers you are talking about are the oscillator trimmers that can only do anything, are only active, if the oscillator is working. I can put them in any position and they do nothing. They aren't shorted. They are perfectly good but not active because the oscillator is dead.
:::::::::::::::: C-18 is brand new. It doesn't have any problems. One end is connected to the chassis and the other end is connected to a resistor. R3. I'll double check that it's also connected to the dead oscillator coil. It's not open. It just refuses to oscillate. All 11 paper and 2 electrolytic capacitors have been replaced. The positives of the electrolytic capacitors connect to the same place and the negatives connect to two different places.
:::::::::::::::: I am getting close to removing the oscillator coil and replacing it or rewinding this one. If only I had the specs for this one. The part number on it is: 2DT200. Maybe someone has an Emerson specs book.
::::::::::::::::
::::::::::::::::Thanks,
::::::::::::::::
::::::::::::::::Dave
::::::::::::::::
:::::::::::::::::Dave,
:::::::::::::::::The oscillator has 2 trimmers in BC mode. One on the tuning cap (C-3) and the other at the rear (C-5), either of which could hamper operation if misadjusted. The one at C-3 is common to both SW and BC. Check C-18. Also, when you tested the IF, (456kHz) were you using signal levels low to moderate or high enough to blast through at any freq?
:::::::::::::::::
:::::::::::::::::marv
:::::::::::::::::
::::::::::::::::::Marv,
:::::::::::::::::: The resistors are the correct value. I checked them. I never replaced them. I also knew that the long black capacitor looking devices were also resistors. They are all correct. The capacitors are in the correct places. Nothing has been changed.
:::::::::::::::::: I'll check the voltage and double check for "birdies". I think I did hear them. My huge isolation transformer is getting a lot of use on this restoration.
::::::::::::::::::
::::::::::::::::::Thanks,
::::::::::::::::::
::::::::::::::::::Dave
::::::::::::::::::
:::::::::::::::::::Dave,
:::::::::::::::::::In reading your 2 posts, I assume the set never worked and you re-capped and replaced bad resistors first. In this case, did you replace the parts just as they were originally installed, but did you also verify their placement via the schematic?
:::::::::::::::::::
:::::::::::::::::::marv
:::::::::::::::::::
::::::::::::::::::::Radiodoc,
:::::::::::::::::::: I just tried that and it makes absolutely no difference whatsoever.
:::::::::::::::::::: What do I look at next?
::::::::::::::::::::
::::::::::::::::::::Thanks,
::::::::::::::::::::
:::::::::::::::::::::Dave,
:::::::::::::::::::::
:::::::::::::::::::::The 98 volts is probably ok. If all else failed and as a shot in the dark, I would reverse the coil leads on the non-tuned winding between B+ and the oscillator "plate" and see what happens.
:::::::::::::::::::::
:::::::::::::::::::::Radiodoc
:::::::::::::::::::::***************
:::::::::::::::::::::
::::::::::::::::::::::Radiodoc,
:::::::::::::::::::::: I took out the oscillator coil and checked every connection and all are good (Perfect), no opens. I checked and cleaned the band switch several times. I replaced C9 several times. When I connect 456 Kc to it from my RF signal generator, it receives that tone perfectly. It blasts!! But it wont take what's presented to it from the antenna terminals and convert that to 456 Kc. It absolutely refuses to do that under any circumstances.
:::::::::::::::::::::: I checked all the connections and they are perfectly perfectly perfect. The resistors are all the correct values. The solder connections have been re-done and they are nice and shiny.
:::::::::::::::::::::: I tried 3 different 6A7 tubes and none of them make any difference.
:::::::::::::::::::::: I checked to make sure that the tuning capacitor or trimmer have any shorts on the oscillator side and there are no shorts. When the set is on and I try to adjust the oscillator screw or short the rotor with the stator on the oscillator side it makes no difference at all. All it's doing is "TRFing". The person who owns this radio MUST have the radio working immediately. I must continue working on it until it works. What do I do next? How do I convert it to a TRF receiver?
::::::::::::::::::::::
::::::::::::::::::::::Thanks,
::::::::::::::::::::::
::::::::::::::::::::::Dave
:::::::::::::::::::::::Radiodoc,
::::::::::::::::::::::: B+ is 98 volts. Is that low? Shouldn't it be a little higher? I can't see any way to raise it. Filament voltage on the 6A7 is 5.3 volts.
:::::::::::::::::::::::
:::::::::::::::::::::::Thanks,
:::::::::::::::::::::::
:::::::::::::::::::::::Dave
::::::::::::::::::::::::Radiodoc,
:::::::::::::::::::::::: C9 is a 100 pf capacitor. I replaced it and it made absolutely no difference.
::::::::::::::::::::::::
::::::::::::::::::::::::Dave
:::::::::::::::::::::::::Dave,
:::::::::::::::::::::::::
:::::::::::::::::::::::::If all fails, walk away for a while and then come back and check carefully all the wiring around the osc circuit for correctness and good solder joints. Did you check C9 (probably a mica)or replace it. If not may try substituting another. Voltage checks on the stage may give a clue if any are off very much.
:::::::::::::::::::::::::
:::::::::::::::::::::::::Radiodoc
:::::::::::::::::::::::::***********
:::::::::::::::::::::::::
:::::::::::::::::::::::::
::::::::::::::::::::::::::Hello All,
:::::::::::::::::::::::::: I have checked everything and the oscillator absolutely refuses to work. All paper and filter capacitors have been replaced. No part of the oscillator coil is open. The resistors are good. I tried a few 6A7s and it still wont work. What to I look at next?
:::::::::::::::::::::::::: This is an AC/DC set. There's not that much there.
::::::::::::::::::::::::::
::::::::::::::::::::::::::Thanks,
::::::::::::::::::::::::::
::::::::::::::::::::::::::Dave
Is it possible to have a high impedance short cathode to grid 1? You can only verify this by removing components from one or the other and measure with tube in and out.
marv
:Marv,
: I have the antenna wire connected to a very large antenna. I'll say it again. I receive 3 stations. The first station is at 570Kc, the second station is at 620Kc, and the third is at 1490Kc. As I turn past 620Kc, I continue to hear 620Kc all through the band but more faintly than I do at 620Kc. When I get to 1490Kc I can hear that station mixed with 620Kc. That's all it receives even if the oscillator coil is disconnected from the oscillator side of the tuning capacitor. The tuning capacitor works perfectly. There are no shorts between plates. The trimmer is fine too. The oscillator remains dead.
:
:What do I look at next?
:
:Thanks,
:
:Dave
::Dave,
::How are you verifying osc operation DMM, VTVM, O'scope, looking for 456kHz at the 6A7 plate, looking for osc at the tank ckt, grids 1, 2, cathode? Keep in mind that even with a working oscillator, the lack of RF through that VERY UNUSUAL antenna transformer will not produce 456kHz. The tuning you described earlier from local stations at 570kHz on the low end tuning and 620kHz at the high end would suggest problems in the set's RF path or severe harmonic content from the station. If the detection was taking place in the audio stage(s), tuning should have no affect.
::
::marv
::
:::Bill,
::: C8 is brand new. It is a bypass capacitor. The old waxy one was removed from the radio about a week ago. The circuit updates don't seem to have anything to do with the oscillator. The 456 Kc part of the radio works fine.
::: When I attempted to look at C8, R9 (500K), in another part of the radio, fell apart. Also one of the leads fell off of a flexible resistor R2. So I had to replace them. I re-soldered the wire C8 wire to the 6A7 pin and it made absolutely no difference. The oscillator is still dead.
:::
::: I do notice now that when the set is on a while, the B+ voltage goes down to 85 volts. These are brand new filter capacitors. So that cannot be the problem. I'll just have to replace every resistor, including the flexible ones. Those crimps onto the carbon must all be failing. I have tons of NOS old style resistors.
:::The Oscillator is still Dead Dead Dead.
::: I'll replace the resistors and let everyone know if the oscillator starts to work. It will probably never work. I'll also try 7 or 8 more 6A7s.
::: What should I look at next?
:::
:::Thanks,
:::
:::Dave
::::Dave, I'm too slow (both ways) to keep up with this thread. But I got to wade in. C-8 is one to recheck, off the 6A7 screen. Also, just curious, did you need to make the changes to R-9, 11, & 12, and C-13 & 14 based on your serial number?
::::
::::Bill VA
::::
::::
:::::Radiodoc,
::::: I just looked through the archives and found that if the voltage is positive it means that the oscillator is not operating. This is what I have been trying to tell you. The oscillator is dead. Ok, good, now we have absolute proof that the oscillator is dead. Now what do I look for? There could still be something not working. The oscillator coil? There is continuity but I don't know what it's value is in micro-henries. All I know is that it's a transformer. It has two primaries for the two bands, and one secondary. The part number on the oscillator coil 2DT200 matches the number in the service data. So it is original.
::::: I'll keep checking the archives to see what others have done in this situation. I think that this may be a common problem. If you know what to check please let me know.
:::::
:::::Thanks,
:::::
:::::Dave
::::::
::::::Radiodoc,
:::::: Yes, it is positive. Pin 5 is 2.4 volts and pin 6 is 2.8 volts now. The only pins that are negative are the filament pins which are -23 volts DC with respect to the chassis. But they are 6.8 volts AC when I measure across the filament.
:::::: Is there something else wrong elsewhere in the set that's preventing the oscillator from working?
::::::
::::::Thanks,
::::::
::::::Dave
::::::
:::::::Radiodoc,
::::::: It was 2.2 volts and it wasn't minus. What would be wrong if it's positive?
::::::: I'm going to double check that voltage.
:::::::
:::::::Thanks,
:::::::
:::::::Dave
::::::::Dave,
::::::::
::::::::With the radio off did you try measuring between adjacent pins (with tube removed) to see if possibly there is an arc over between pins. You mentioned there was 2 volts on the oscillator grid. There should be a negative voltage on the oscillator grid unless you forgot to type a minus sign in front of the voltage reading you posted.
::::::::
::::::::Radiodoc
::::::::************
::::::::
:::::::::Marv,
::::::::: The connections and the voltages are quite good. But it still wont oscillate. It works and absolutely refuses to work all at the same time.
:::::::::
:::::::::Thanks,
:::::::::
:::::::::Dave
::::::::::Marv,
:::::::::: Yes they are. I measure the pin and the contact and I get the same reading from both. But I'll double check.
::::::::::
::::::::::Thanks,
::::::::::
::::::::::Dave
:::::::::::Dave,
:::::::::::You have eliminated almost everything. There is one remaining item though. Are you sure the socket/tube pin connections are firm?
:::::::::::
:::::::::::marv
:::::::::::
::::::::::::Edd,
:::::::::::: This oscillator is dead, dead, dead. A transistor radio will pick up nothing from it. Also, the radio works exactly the same way whether the oscillator coil is connected to the oscillator side of the tuning capacitor or not. No difference. It absolutely refuses to oscillate even though all is connected perfectly. All components are good too (except for I believe, the oscillator coil). I have more than qadruple checked the 30K, 50K, and 300 whatever ohm resistors. They are hooked up correctly. Also, the another 100pf capacitor was tried and it makes no difference. It's still dead dead dead.
:::::::::::: I don't quite understand what you want me to do with the B & K. But I was able to use the B & K to "tune" the radio in the CW position. The rest of the radio receives the 460 Kc perfectly. So it's ready for the oscillator/mixer circuit to work. I am getting ready to replace the oscillator coil. I think I can take one from another AC/DC set just to try it out. Can I do that? I see the that there is a B+ side (output) and the other side that connects to the oscillator side of the tuning capacitor. I think that the second I replace the oscillator coil it will work perfectly. Please correct me if I'm wrong.
:::::::::::: The oscillator coil has two sections on it. One is the Litz wire and the other is the enameled wire.
:::::::::::: I think that what you want me to do at the junction of c1 and R9 is to inject an oscillation to see if I can then tune the radio normally with its tuning capacitor.
::::::::::::
::::::::::::Thanks,
::::::::::::
::::::::::::Dave
:::::::::::::
:::::::::::::
:::::::::::::
:::::::::::::
:::::::::::::After reviewing your last postings info:
:::::::::::::My fustus “querstion” was if the radio operated in some degree of receiving stations ? via a tunable superheterodyne action / mode prior to the mass recapping of the unit ?
:::::::::::::
:::::::::::::
:::::::::::::
:::::::::::::Can we assume that C9..100 mmfd was ok and not even messed with ?
:::::::::::::Is cathode resistor R2 wired up ok and at its ~350 ohm value ?
:::::::::::::As well as the grid resistor of R1 ….50k wired properly and at its value ?
:::::::::::::The last item which I am sure that you did get involved with was the cathode bypass Condenser C7….05 ufd and it is OK and was reinstalled to the correct terminals…right…as that is also as critical as the 3 companion items.
:::::::::::::
:::::::::::::
:::::::::::::
:::::::::::::Looks as if the oscillator coil is on the larger ½ to ¾ in coil form and and a Litz wound unit in a tight layer…rather than the old style of enameled wire wound the full length of a long coil form. Plus, you seem to attest of its wirings continuity integrity as well as the adjunct tuning cap and its trimmer caps not being shorted out or dragging plates. Plus the additional reverting of one of the windings for a proper feed back phase check.
:::::::::::::Also with your BEE und KAY, you should be able to couple its input into the first grid of the mixer and at the proper injection of CW RF level, be able to swing its dial thru the 1005-2195 khc range and tune thru your stronger receptive stations in the area, with the two “TRF” stations being the powerhouses, BUT with the necessity of having to manually tune the tuning condenser in order to optimize the RF section being in resonance with them, when trying for weaker stations in bringing up received reception level..
:::::::::::::
:::::::::::::
:::::::::::::
:::::::::::::To further ease your mind about the radios oscillator sections L-C combinations , you could go to the juncture of C9 and R1 and couple in CW RF via a series / isolative ~100 pf cap and go to the same junction and tack on an anode of a 1N34 / 60 / 64 / 270 GERMANIUM diode and at its cathodes end , take a .001 cap for bypassing to ground and then meter the cathodes output via a VTVM.
:::::::::::::
:::::::::::::
:::::::::::::(N0…1N 914’s/4148’s/1N400oseries for this application)(Radio Shack stocks them in case you don’t have one from an oooold generation AM transistor radio chassis or from the building of a crystal set.)
:::::::::::::
:::::::::::::
:::::::::::::
:::::::::::::Then if you will power up the BEE und KAY and place in its CW mode and set the Emerson…(No power required....as this testing will be passive)…to the 1/3 lower end of the dial 700 kc ish (tuning cap ~ ¾ meshed)
:::::::::::::Then you tune the B & K in the ~1000-1400 range and see if the co-joined parasitic tuned oscillators circuit doesn’t give you a rising / declining reading as resonance was scanned across.
:::::::::::::Then, hop the radios tuning up to the higher third of the band (tuning cap ~ 1/4 meshed) and test for a like reading of a viable resonant circuit pair working at that
:::::::::::::frequency also.
:::::::::::::Thereby you have merely temp- rigged up a “po boys” grid dipper to interpret the presence of a functioning / resonating effect by the osc sections variable L-C pair and it having some degree of “Q”.
:::::::::::::
:::::::::::::
:::::::::::::The other alternative being that recurrent sweep Eico 460 Scope / Kluge of yours, so I think that with the former detected and metered RF , you would be much better off.
:::::::::::::
:::::::::::::
:::::::::::::
:::::::::::::Addenda:
:::::::::::::Noticed your new readings just at this posting time, and the bucolic local osc grid voltages reading. And have you confirmed that there is even any level oscillation by the taking of a portable xstr radios ferri-loop and placing it atop the osc coil winding and tune it off station just onto the very edge / sideband of a weaker ~1400-1740 kc AM station and then run the operating radio's tuning condenser across the bottom half of the AM band to see if even a weak heterodyning / birdie is heard on the xstr radio.
:::::::::::::
:::::::::::::Standing by for feed back
:::::::::::::
:::::::::::::
:::::::::::::73's de Edd
:::::::::::::
:::::::::::::
:::::::::::::
:::::::::::::
:::::::::::::
:::::::::::::
:::::::::::::
:::::::::::::
:::::::::::::
:::::::::::::
::::::::::::::Marv and all,
::::::::::::::
:::::::::::::: Here are the voltage readings on the 6A7 tube.
::::::::::::::
::::::::::::::Pins 1 & 7: 6.8 volts AC (Filament)
::::::::::::::Pin 2: 107.5 v DC (Plate)
::::::::::::::Pin 3: 43.5 volts DC (G3 and G5)
::::::::::::::Pin 4: 106.7 volts (G2)
::::::::::::::Pin 5: 2.2 V DC (G1)
::::::::::::::Pin 6: 2.647 volts DC (Cathode)
::::::::::::::Cap: -.361 v DC (G4)
::::::::::::::
::::::::::::::These seem like pretty healthy voltages to me. I don't see anything wrong there. The IF transformer is connecting B+ to the plate and the Oscillator coil is connecting B+ to to pin 4. So neither coil is open.
::::::::::::::
::::::::::::::I did notice that C17 was missing. I put it back and it might have made an improvement but not with the oscillator.
::::::::::::::
::::::::::::::Please if anyone has anymore ideas before I "attack" (very closely examine) the oscillator coil, please help.
::::::::::::::
::::::::::::::Thanks,
::::::::::::::
::::::::::::::Dave
::::::::::::::
:::::::::::::::Marv,
::::::::::::::: My RF signal generator modulates a 400 Hz tone on the 456 Kc carrier frequency when it's set to 456 Kc. The part of the radio that the signal generator is connected to is tune to exactly tuned to 456 Kc. It can receive 456 Kc and only 456 Kc. That "station" is received and I can blast the 400 Hz tone through the speaker of the radio. If I change the RF signal generator to another frequency, then no 400 Hz tone is heard. It is as perfectly aligned as I can get it. It may not have the best adjacent channel rejection but the signal is the strongest when the signal generator is set to 456 Kc.
::::::::::::::: The front part of the radio is what I'm having trouble with, and NOT the 456 Kc area. The radio is not converting (moving) the received frequency to 456 Kc. I can hear 570 Kc near the low end of the band and 620 Kc near the high end of the band (I live right near the brodcast antennas for these stations). That's all it does. It absolutely refuses to oscillate under any circumstances. I have checked about all I can check. All is working and not working at the same time.
::::::::::::::: The trimmers you are talking about are the oscillator trimmers that can only do anything, are only active, if the oscillator is working. I can put them in any position and they do nothing. They aren't shorted. They are perfectly good but not active because the oscillator is dead.
::::::::::::::: C-18 is brand new. It doesn't have any problems. One end is connected to the chassis and the other end is connected to a resistor. R3. I'll double check that it's also connected to the dead oscillator coil. It's not open. It just refuses to oscillate. All 11 paper and 2 electrolytic capacitors have been replaced. The positives of the electrolytic capacitors connect to the same place and the negatives connect to two different places.
::::::::::::::: I am getting close to removing the oscillator coil and replacing it or rewinding this one. If only I had the specs for this one. The part number on it is: 2DT200. Maybe someone has an Emerson specs book.
:::::::::::::::
:::::::::::::::Thanks,
:::::::::::::::
:::::::::::::::Dave
:::::::::::::::
::::::::::::::::Dave,
::::::::::::::::The oscillator has 2 trimmers in BC mode. One on the tuning cap (C-3) and the other at the rear (C-5), either of which could hamper operation if misadjusted. The one at C-3 is common to both SW and BC. Check C-18. Also, when you tested the IF, (456kHz) were you using signal levels low to moderate or high enough to blast through at any freq?
::::::::::::::::
::::::::::::::::marv
::::::::::::::::
:::::::::::::::::Marv,
::::::::::::::::: The resistors are the correct value. I checked them. I never replaced them. I also knew that the long black capacitor looking devices were also resistors. They are all correct. The capacitors are in the correct places. Nothing has been changed.
::::::::::::::::: I'll check the voltage and double check for "birdies". I think I did hear them. My huge isolation transformer is getting a lot of use on this restoration.
:::::::::::::::::
:::::::::::::::::Thanks,
:::::::::::::::::
:::::::::::::::::Dave
:::::::::::::::::
::::::::::::::::::Dave,
::::::::::::::::::In reading your 2 posts, I assume the set never worked and you re-capped and replaced bad resistors first. In this case, did you replace the parts just as they were originally installed, but did you also verify their placement via the schematic?
::::::::::::::::::
::::::::::::::::::marv
::::::::::::::::::
:::::::::::::::::::Radiodoc,
::::::::::::::::::: I just tried that and it makes absolutely no difference whatsoever.
::::::::::::::::::: What do I look at next?
:::::::::::::::::::
:::::::::::::::::::Thanks,
:::::::::::::::::::
::::::::::::::::::::Dave,
::::::::::::::::::::
::::::::::::::::::::The 98 volts is probably ok. If all else failed and as a shot in the dark, I would reverse the coil leads on the non-tuned winding between B+ and the oscillator "plate" and see what happens.
::::::::::::::::::::
::::::::::::::::::::Radiodoc
::::::::::::::::::::***************
::::::::::::::::::::
:::::::::::::::::::::Radiodoc,
::::::::::::::::::::: I took out the oscillator coil and checked every connection and all are good (Perfect), no opens. I checked and cleaned the band switch several times. I replaced C9 several times. When I connect 456 Kc to it from my RF signal generator, it receives that tone perfectly. It blasts!! But it wont take what's presented to it from the antenna terminals and convert that to 456 Kc. It absolutely refuses to do that under any circumstances.
::::::::::::::::::::: I checked all the connections and they are perfectly perfectly perfect. The resistors are all the correct values. The solder connections have been re-done and they are nice and shiny.
::::::::::::::::::::: I tried 3 different 6A7 tubes and none of them make any difference.
::::::::::::::::::::: I checked to make sure that the tuning capacitor or trimmer have any shorts on the oscillator side and there are no shorts. When the set is on and I try to adjust the oscillator screw or short the rotor with the stator on the oscillator side it makes no difference at all. All it's doing is "TRFing". The person who owns this radio MUST have the radio working immediately. I must continue working on it until it works. What do I do next? How do I convert it to a TRF receiver?
:::::::::::::::::::::
:::::::::::::::::::::Thanks,
:::::::::::::::::::::
:::::::::::::::::::::Dave
::::::::::::::::::::::Radiodoc,
:::::::::::::::::::::: B+ is 98 volts. Is that low? Shouldn't it be a little higher? I can't see any way to raise it. Filament voltage on the 6A7 is 5.3 volts.
::::::::::::::::::::::
::::::::::::::::::::::Thanks,
::::::::::::::::::::::
::::::::::::::::::::::Dave
:::::::::::::::::::::::Radiodoc,
::::::::::::::::::::::: C9 is a 100 pf capacitor. I replaced it and it made absolutely no difference.
:::::::::::::::::::::::
:::::::::::::::::::::::Dave
::::::::::::::::::::::::Dave,
::::::::::::::::::::::::
::::::::::::::::::::::::If all fails, walk away for a while and then come back and check carefully all the wiring around the osc circuit for correctness and good solder joints. Did you check C9 (probably a mica)or replace it. If not may try substituting another. Voltage checks on the stage may give a clue if any are off very much.
::::::::::::::::::::::::
::::::::::::::::::::::::Radiodoc
::::::::::::::::::::::::***********
::::::::::::::::::::::::
::::::::::::::::::::::::
:::::::::::::::::::::::::Hello All,
::::::::::::::::::::::::: I have checked everything and the oscillator absolutely refuses to work. All paper and filter capacitors have been replaced. No part of the oscillator coil is open. The resistors are good. I tried a few 6A7s and it still wont work. What to I look at next?
::::::::::::::::::::::::: This is an AC/DC set. There's not that much there.
:::::::::::::::::::::::::
:::::::::::::::::::::::::Thanks,
:::::::::::::::::::::::::
:::::::::::::::::::::::::Dave
In my last posting I meant to say "high impedance short in the socket", and of course testing in the unpowered mode.
marv
:Marv,
: I have the antenna wire connected to a very large antenna. I'll say it again. I receive 3 stations. The first station is at 570Kc, the second station is at 620Kc, and the third is at 1490Kc. As I turn past 620Kc, I continue to hear 620Kc all through the band but more faintly than I do at 620Kc. When I get to 1490Kc I can hear that station mixed with 620Kc. That's all it receives even if the oscillator coil is disconnected from the oscillator side of the tuning capacitor. The tuning capacitor works perfectly. There are no shorts between plates. The trimmer is fine too. The oscillator remains dead.
:
:What do I look at next?
:
:Thanks,
:
:Dave
::Dave,
::How are you verifying osc operation DMM, VTVM, O'scope, looking for 456kHz at the 6A7 plate, looking for osc at the tank ckt, grids 1, 2, cathode? Keep in mind that even with a working oscillator, the lack of RF through that VERY UNUSUAL antenna transformer will not produce 456kHz. The tuning you described earlier from local stations at 570kHz on the low end tuning and 620kHz at the high end would suggest problems in the set's RF path or severe harmonic content from the station. If the detection was taking place in the audio stage(s), tuning should have no affect.
::
::marv
::
:::Bill,
::: C8 is brand new. It is a bypass capacitor. The old waxy one was removed from the radio about a week ago. The circuit updates don't seem to have anything to do with the oscillator. The 456 Kc part of the radio works fine.
::: When I attempted to look at C8, R9 (500K), in another part of the radio, fell apart. Also one of the leads fell off of a flexible resistor R2. So I had to replace them. I re-soldered the wire C8 wire to the 6A7 pin and it made absolutely no difference. The oscillator is still dead.
:::
::: I do notice now that when the set is on a while, the B+ voltage goes down to 85 volts. These are brand new filter capacitors. So that cannot be the problem. I'll just have to replace every resistor, including the flexible ones. Those crimps onto the carbon must all be failing. I have tons of NOS old style resistors.
:::The Oscillator is still Dead Dead Dead.
::: I'll replace the resistors and let everyone know if the oscillator starts to work. It will probably never work. I'll also try 7 or 8 more 6A7s.
::: What should I look at next?
:::
:::Thanks,
:::
:::Dave
::::Dave, I'm too slow (both ways) to keep up with this thread. But I got to wade in. C-8 is one to recheck, off the 6A7 screen. Also, just curious, did you need to make the changes to R-9, 11, & 12, and C-13 & 14 based on your serial number?
::::
::::Bill VA
::::
::::
:::::Radiodoc,
::::: I just looked through the archives and found that if the voltage is positive it means that the oscillator is not operating. This is what I have been trying to tell you. The oscillator is dead. Ok, good, now we have absolute proof that the oscillator is dead. Now what do I look for? There could still be something not working. The oscillator coil? There is continuity but I don't know what it's value is in micro-henries. All I know is that it's a transformer. It has two primaries for the two bands, and one secondary. The part number on the oscillator coil 2DT200 matches the number in the service data. So it is original.
::::: I'll keep checking the archives to see what others have done in this situation. I think that this may be a common problem. If you know what to check please let me know.
:::::
:::::Thanks,
:::::
:::::Dave
::::::
::::::Radiodoc,
:::::: Yes, it is positive. Pin 5 is 2.4 volts and pin 6 is 2.8 volts now. The only pins that are negative are the filament pins which are -23 volts DC with respect to the chassis. But they are 6.8 volts AC when I measure across the filament.
:::::: Is there something else wrong elsewhere in the set that's preventing the oscillator from working?
::::::
::::::Thanks,
::::::
::::::Dave
::::::
:::::::Radiodoc,
::::::: It was 2.2 volts and it wasn't minus. What would be wrong if it's positive?
::::::: I'm going to double check that voltage.
:::::::
:::::::Thanks,
:::::::
:::::::Dave
::::::::Dave,
::::::::
::::::::With the radio off did you try measuring between adjacent pins (with tube removed) to see if possibly there is an arc over between pins. You mentioned there was 2 volts on the oscillator grid. There should be a negative voltage on the oscillator grid unless you forgot to type a minus sign in front of the voltage reading you posted.
::::::::
::::::::Radiodoc
::::::::************
::::::::
:::::::::Marv,
::::::::: The connections and the voltages are quite good. But it still wont oscillate. It works and absolutely refuses to work all at the same time.
:::::::::
:::::::::Thanks,
:::::::::
:::::::::Dave
::::::::::Marv,
:::::::::: Yes they are. I measure the pin and the contact and I get the same reading from both. But I'll double check.
::::::::::
::::::::::Thanks,
::::::::::
::::::::::Dave
:::::::::::Dave,
:::::::::::You have eliminated almost everything. There is one remaining item though. Are you sure the socket/tube pin connections are firm?
:::::::::::
:::::::::::marv
:::::::::::
::::::::::::Edd,
:::::::::::: This oscillator is dead, dead, dead. A transistor radio will pick up nothing from it. Also, the radio works exactly the same way whether the oscillator coil is connected to the oscillator side of the tuning capacitor or not. No difference. It absolutely refuses to oscillate even though all is connected perfectly. All components are good too (except for I believe, the oscillator coil). I have more than qadruple checked the 30K, 50K, and 300 whatever ohm resistors. They are hooked up correctly. Also, the another 100pf capacitor was tried and it makes no difference. It's still dead dead dead.
:::::::::::: I don't quite understand what you want me to do with the B & K. But I was able to use the B & K to "tune" the radio in the CW position. The rest of the radio receives the 460 Kc perfectly. So it's ready for the oscillator/mixer circuit to work. I am getting ready to replace the oscillator coil. I think I can take one from another AC/DC set just to try it out. Can I do that? I see the that there is a B+ side (output) and the other side that connects to the oscillator side of the tuning capacitor. I think that the second I replace the oscillator coil it will work perfectly. Please correct me if I'm wrong.
:::::::::::: The oscillator coil has two sections on it. One is the Litz wire and the other is the enameled wire.
:::::::::::: I think that what you want me to do at the junction of c1 and R9 is to inject an oscillation to see if I can then tune the radio normally with its tuning capacitor.
::::::::::::
::::::::::::Thanks,
::::::::::::
::::::::::::Dave
:::::::::::::
:::::::::::::
:::::::::::::
:::::::::::::
:::::::::::::After reviewing your last postings info:
:::::::::::::My fustus “querstion” was if the radio operated in some degree of receiving stations ? via a tunable superheterodyne action / mode prior to the mass recapping of the unit ?
:::::::::::::
:::::::::::::
:::::::::::::
:::::::::::::Can we assume that C9..100 mmfd was ok and not even messed with ?
:::::::::::::Is cathode resistor R2 wired up ok and at its ~350 ohm value ?
:::::::::::::As well as the grid resistor of R1 ….50k wired properly and at its value ?
:::::::::::::The last item which I am sure that you did get involved with was the cathode bypass Condenser C7….05 ufd and it is OK and was reinstalled to the correct terminals…right…as that is also as critical as the 3 companion items.
:::::::::::::
:::::::::::::
:::::::::::::
:::::::::::::Looks as if the oscillator coil is on the larger ½ to ¾ in coil form and and a Litz wound unit in a tight layer…rather than the old style of enameled wire wound the full length of a long coil form. Plus, you seem to attest of its wirings continuity integrity as well as the adjunct tuning cap and its trimmer caps not being shorted out or dragging plates. Plus the additional reverting of one of the windings for a proper feed back phase check.
:::::::::::::Also with your BEE und KAY, you should be able to couple its input into the first grid of the mixer and at the proper injection of CW RF level, be able to swing its dial thru the 1005-2195 khc range and tune thru your stronger receptive stations in the area, with the two “TRF” stations being the powerhouses, BUT with the necessity of having to manually tune the tuning condenser in order to optimize the RF section being in resonance with them, when trying for weaker stations in bringing up received reception level..
:::::::::::::
:::::::::::::
:::::::::::::
:::::::::::::To further ease your mind about the radios oscillator sections L-C combinations , you could go to the juncture of C9 and R1 and couple in CW RF via a series / isolative ~100 pf cap and go to the same junction and tack on an anode of a 1N34 / 60 / 64 / 270 GERMANIUM diode and at its cathodes end , take a .001 cap for bypassing to ground and then meter the cathodes output via a VTVM.
:::::::::::::
:::::::::::::
:::::::::::::(N0…1N 914’s/4148’s/1N400oseries for this application)(Radio Shack stocks them in case you don’t have one from an oooold generation AM transistor radio chassis or from the building of a crystal set.)
:::::::::::::
:::::::::::::
:::::::::::::
:::::::::::::Then if you will power up the BEE und KAY and place in its CW mode and set the Emerson…(No power required....as this testing will be passive)…to the 1/3 lower end of the dial 700 kc ish (tuning cap ~ ¾ meshed)
:::::::::::::Then you tune the B & K in the ~1000-1400 range and see if the co-joined parasitic tuned oscillators circuit doesn’t give you a rising / declining reading as resonance was scanned across.
:::::::::::::Then, hop the radios tuning up to the higher third of the band (tuning cap ~ 1/4 meshed) and test for a like reading of a viable resonant circuit pair working at that
:::::::::::::frequency also.
:::::::::::::Thereby you have merely temp- rigged up a “po boys” grid dipper to interpret the presence of a functioning / resonating effect by the osc sections variable L-C pair and it having some degree of “Q”.
:::::::::::::
:::::::::::::
:::::::::::::The other alternative being that recurrent sweep Eico 460 Scope / Kluge of yours, so I think that with the former detected and metered RF , you would be much better off.
:::::::::::::
:::::::::::::
:::::::::::::
:::::::::::::Addenda:
:::::::::::::Noticed your new readings just at this posting time, and the bucolic local osc grid voltages reading. And have you confirmed that there is even any level oscillation by the taking of a portable xstr radios ferri-loop and placing it atop the osc coil winding and tune it off station just onto the very edge / sideband of a weaker ~1400-1740 kc AM station and then run the operating radio's tuning condenser across the bottom half of the AM band to see if even a weak heterodyning / birdie is heard on the xstr radio.
:::::::::::::
:::::::::::::Standing by for feed back
:::::::::::::
:::::::::::::
:::::::::::::73's de Edd
:::::::::::::
:::::::::::::
:::::::::::::
:::::::::::::
:::::::::::::
:::::::::::::
:::::::::::::
:::::::::::::
:::::::::::::
:::::::::::::
::::::::::::::Marv and all,
::::::::::::::
:::::::::::::: Here are the voltage readings on the 6A7 tube.
::::::::::::::
::::::::::::::Pins 1 & 7: 6.8 volts AC (Filament)
::::::::::::::Pin 2: 107.5 v DC (Plate)
::::::::::::::Pin 3: 43.5 volts DC (G3 and G5)
::::::::::::::Pin 4: 106.7 volts (G2)
::::::::::::::Pin 5: 2.2 V DC (G1)
::::::::::::::Pin 6: 2.647 volts DC (Cathode)
::::::::::::::Cap: -.361 v DC (G4)
::::::::::::::
::::::::::::::These seem like pretty healthy voltages to me. I don't see anything wrong there. The IF transformer is connecting B+ to the plate and the Oscillator coil is connecting B+ to to pin 4. So neither coil is open.
::::::::::::::
::::::::::::::I did notice that C17 was missing. I put it back and it might have made an improvement but not with the oscillator.
::::::::::::::
::::::::::::::Please if anyone has anymore ideas before I "attack" (very closely examine) the oscillator coil, please help.
::::::::::::::
::::::::::::::Thanks,
::::::::::::::
::::::::::::::Dave
::::::::::::::
:::::::::::::::Marv,
::::::::::::::: My RF signal generator modulates a 400 Hz tone on the 456 Kc carrier frequency when it's set to 456 Kc. The part of the radio that the signal generator is connected to is tune to exactly tuned to 456 Kc. It can receive 456 Kc and only 456 Kc. That "station" is received and I can blast the 400 Hz tone through the speaker of the radio. If I change the RF signal generator to another frequency, then no 400 Hz tone is heard. It is as perfectly aligned as I can get it. It may not have the best adjacent channel rejection but the signal is the strongest when the signal generator is set to 456 Kc.
::::::::::::::: The front part of the radio is what I'm having trouble with, and NOT the 456 Kc area. The radio is not converting (moving) the received frequency to 456 Kc. I can hear 570 Kc near the low end of the band and 620 Kc near the high end of the band (I live right near the brodcast antennas for these stations). That's all it does. It absolutely refuses to oscillate under any circumstances. I have checked about all I can check. All is working and not working at the same time.
::::::::::::::: The trimmers you are talking about are the oscillator trimmers that can only do anything, are only active, if the oscillator is working. I can put them in any position and they do nothing. They aren't shorted. They are perfectly good but not active because the oscillator is dead.
::::::::::::::: C-18 is brand new. It doesn't have any problems. One end is connected to the chassis and the other end is connected to a resistor. R3. I'll double check that it's also connected to the dead oscillator coil. It's not open. It just refuses to oscillate. All 11 paper and 2 electrolytic capacitors have been replaced. The positives of the electrolytic capacitors connect to the same place and the negatives connect to two different places.
::::::::::::::: I am getting close to removing the oscillator coil and replacing it or rewinding this one. If only I had the specs for this one. The part number on it is: 2DT200. Maybe someone has an Emerson specs book.
:::::::::::::::
:::::::::::::::Thanks,
:::::::::::::::
:::::::::::::::Dave
:::::::::::::::
::::::::::::::::Dave,
::::::::::::::::The oscillator has 2 trimmers in BC mode. One on the tuning cap (C-3) and the other at the rear (C-5), either of which could hamper operation if misadjusted. The one at C-3 is common to both SW and BC. Check C-18. Also, when you tested the IF, (456kHz) were you using signal levels low to moderate or high enough to blast through at any freq?
::::::::::::::::
::::::::::::::::marv
::::::::::::::::
:::::::::::::::::Marv,
::::::::::::::::: The resistors are the correct value. I checked them. I never replaced them. I also knew that the long black capacitor looking devices were also resistors. They are all correct. The capacitors are in the correct places. Nothing has been changed.
::::::::::::::::: I'll check the voltage and double check for "birdies". I think I did hear them. My huge isolation transformer is getting a lot of use on this restoration.
:::::::::::::::::
:::::::::::::::::Thanks,
:::::::::::::::::
:::::::::::::::::Dave
:::::::::::::::::
::::::::::::::::::Dave,
::::::::::::::::::In reading your 2 posts, I assume the set never worked and you re-capped and replaced bad resistors first. In this case, did you replace the parts just as they were originally installed, but did you also verify their placement via the schematic?
::::::::::::::::::
::::::::::::::::::marv
::::::::::::::::::
:::::::::::::::::::Radiodoc,
::::::::::::::::::: I just tried that and it makes absolutely no difference whatsoever.
::::::::::::::::::: What do I look at next?
:::::::::::::::::::
:::::::::::::::::::Thanks,
:::::::::::::::::::
::::::::::::::::::::Dave,
::::::::::::::::::::
::::::::::::::::::::The 98 volts is probably ok. If all else failed and as a shot in the dark, I would reverse the coil leads on the non-tuned winding between B+ and the oscillator "plate" and see what happens.
::::::::::::::::::::
::::::::::::::::::::Radiodoc
::::::::::::::::::::***************
::::::::::::::::::::
:::::::::::::::::::::Radiodoc,
::::::::::::::::::::: I took out the oscillator coil and checked every connection and all are good (Perfect), no opens. I checked and cleaned the band switch several times. I replaced C9 several times. When I connect 456 Kc to it from my RF signal generator, it receives that tone perfectly. It blasts!! But it wont take what's presented to it from the antenna terminals and convert that to 456 Kc. It absolutely refuses to do that under any circumstances.
::::::::::::::::::::: I checked all the connections and they are perfectly perfectly perfect. The resistors are all the correct values. The solder connections have been re-done and they are nice and shiny.
::::::::::::::::::::: I tried 3 different 6A7 tubes and none of them make any difference.
::::::::::::::::::::: I checked to make sure that the tuning capacitor or trimmer have any shorts on the oscillator side and there are no shorts. When the set is on and I try to adjust the oscillator screw or short the rotor with the stator on the oscillator side it makes no difference at all. All it's doing is "TRFing". The person who owns this radio MUST have the radio working immediately. I must continue working on it until it works. What do I do next? How do I convert it to a TRF receiver?
:::::::::::::::::::::
:::::::::::::::::::::Thanks,
:::::::::::::::::::::
:::::::::::::::::::::Dave
::::::::::::::::::::::Radiodoc,
:::::::::::::::::::::: B+ is 98 volts. Is that low? Shouldn't it be a little higher? I can't see any way to raise it. Filament voltage on the 6A7 is 5.3 volts.
::::::::::::::::::::::
::::::::::::::::::::::Thanks,
::::::::::::::::::::::
::::::::::::::::::::::Dave
:::::::::::::::::::::::Radiodoc,
::::::::::::::::::::::: C9 is a 100 pf capacitor. I replaced it and it made absolutely no difference.
:::::::::::::::::::::::
:::::::::::::::::::::::Dave
::::::::::::::::::::::::Dave,
::::::::::::::::::::::::
::::::::::::::::::::::::If all fails, walk away for a while and then come back and check carefully all the wiring around the osc circuit for correctness and good solder joints. Did you check C9 (probably a mica)or replace it. If not may try substituting another. Voltage checks on the stage may give a clue if any are off very much.
::::::::::::::::::::::::
::::::::::::::::::::::::Radiodoc
::::::::::::::::::::::::***********
::::::::::::::::::::::::
::::::::::::::::::::::::
:::::::::::::::::::::::::Hello All,
::::::::::::::::::::::::: I have checked everything and the oscillator absolutely refuses to work. All paper and filter capacitors have been replaced. No part of the oscillator coil is open. The resistors are good. I tried a few 6A7s and it still wont work. What to I look at next?
::::::::::::::::::::::::: This is an AC/DC set. There's not that much there.
:::::::::::::::::::::::::
:::::::::::::::::::::::::Thanks,
:::::::::::::::::::::::::
:::::::::::::::::::::::::Dave
A long time ago a guy on this forum had the same trouble with a farm radio he was given. The previous owner had tried to plug it in!!!!!!!!!!!! Well, with all new tubes in place, he still overlooked the oscillator coil. I suggested this to him , but he couldn't get it to work. He said that I should take the radio. ....So, after rewinding the oscillator coil, and then building the radio an AC/DC power supply, the radio now sits proudly upon my fridge, and plays every day. Unfortunately I never could get the oscillator to track perfectly, even though I rewound it several times, and tried various other tricks. The radio won't go all the way to 540KC or 1600KC. It's pretty good otherwise, though. I suppose a professionally wound coil would fix the problem.
Your oscillator section definitely isn't working, though, judging how you describe your set's symptoms.
Make sure that the coils you are using are appropriate for the radio. Make sure that the small coil is on the 2nd grid and B+, and that the large coil is on the 1st grid and B- or AVC, or whatever the schematic suggests. Make sure that when you connect the coil, you also try reversing it. There isn't much to the circuit. Check impedances. Check the tuning condenser for shorts. Check the oscillator coil for opens.
The person who owns the radio finally ordered a universal BC oscillator coil and I hooked it up and "like magic" the radio is working.
Thanks a lot for everyone's help.
Dave
:
:
:
:
:After reviewing your last postings info:
:My fustus “querstion” was if the radio operated in some degree of receiving stations ? via a tunable superheterodyne action / mode prior to the mass recapping of the unit ?
:
:
:
:Can we assume that C9..100 mmfd was ok and not even messed with ?
:Is cathode resistor R2 wired up ok and at its ~350 ohm value ?
:As well as the grid resistor of R1 ….50k wired properly and at its value ?
:The last item which I am sure that you did get involved with was the cathode bypass Condenser C7….05 ufd and it is OK and was reinstalled to the correct terminals…right…as that is also as critical as the 3 companion items.
:
:
:
:Looks as if the oscillator coil is on the larger ½ to ¾ in coil form and and a Litz wound unit in a tight layer…rather than the old style of enameled wire wound the full length of a long coil form. Plus, you seem to attest of its wirings continuity integrity as well as the adjunct tuning cap and its trimmer caps not being shorted out or dragging plates. Plus the additional reverting of one of the windings for a proper feed back phase check.
:Also with your BEE und KAY, you should be able to couple its input into the first grid of the mixer and at the proper injection of CW RF level, be able to swing its dial thru the 1005-2195 khc range and tune thru your stronger receptive stations in the area, with the two “TRF” stations being the powerhouses, BUT with the necessity of having to manually tune the tuning condenser in order to optimize the RF section being in resonance with them, when trying for weaker stations in bringing up received reception level..
:
:
:
:To further ease your mind about the radios oscillator sections L-C combinations , you could go to the juncture of C9 and R1 and couple in CW RF via a series / isolative ~100 pf cap and go to the same junction and tack on an anode of a 1N34 / 60 / 64 / 270 GERMANIUM diode and at its cathodes end , take a .001 cap for bypassing to ground and then meter the cathodes output via a VTVM.
:
:
:(N0…1N 914’s/4148’s/1N400oseries for this application)(Radio Shack stocks them in case you don’t have one from an oooold generation AM transistor radio chassis or from the building of a crystal set.)
:
:
:
:Then if you will power up the BEE und KAY and place in its CW mode and set the Emerson…(No power required....as this testing will be passive)…to the 1/3 lower end of the dial 700 kc ish (tuning cap ~ ¾ meshed)
:Then you tune the B & K in the ~1000-1400 range and see if the co-joined parasitic tuned oscillators circuit doesn’t give you a rising / declining reading as resonance was scanned across.
:Then, hop the radios tuning up to the higher third of the band (tuning cap ~ 1/4 meshed) and test for a like reading of a viable resonant circuit pair working at that
:frequency also.
:Thereby you have merely temp- rigged up a “po boys” grid dipper to interpret the presence of a functioning / resonating effect by the osc sections variable L-C pair and it having some degree of “Q”.
:
:
:The other alternative being that recurrent sweep Eico 460 Scope / Kluge of yours, so I think that with the former detected and metered RF , you would be much better off.
:
:
:
:Addenda:
:Noticed your new readings just at this posting time, and the bucolic local osc grid voltages reading. And have you confirmed that there is even any level oscillation by the taking of a portable xstr radios ferri-loop and placing it atop the osc coil winding and tune it off station just onto the very edge / sideband of a weaker ~1400-1740 kc AM station and then run the operating radio's tuning condenser across the bottom half of the AM band to see if even a weak heterodyning / birdie is heard on the xstr radio.
:
:Standing by for feed back
:
:
:73's de Edd
:
:
:
:
:
:
:
:
:
:
::Marv and all,
::
:: Here are the voltage readings on the 6A7 tube.
::
::Pins 1 & 7: 6.8 volts AC (Filament)
::Pin 2: 107.5 v DC (Plate)
::Pin 3: 43.5 volts DC (G3 and G5)
::Pin 4: 106.7 volts (G2)
::Pin 5: 2.2 V DC (G1)
::Pin 6: 2.647 volts DC (Cathode)
::Cap: -.361 v DC (G4)
::
::These seem like pretty healthy voltages to me. I don't see anything wrong there. The IF transformer is connecting B+ to the plate and the Oscillator coil is connecting B+ to to pin 4. So neither coil is open.
::
::I did notice that C17 was missing. I put it back and it might have made an improvement but not with the oscillator.
::
::Please if anyone has anymore ideas before I "attack" (very closely examine) the oscillator coil, please help.
::
::Thanks,
::
::Dave
::
:::Marv,
::: My RF signal generator modulates a 400 Hz tone on the 456 Kc carrier frequency when it's set to 456 Kc. The part of the radio that the signal generator is connected to is tune to exactly tuned to 456 Kc. It can receive 456 Kc and only 456 Kc. That "station" is received and I can blast the 400 Hz tone through the speaker of the radio. If I change the RF signal generator to another frequency, then no 400 Hz tone is heard. It is as perfectly aligned as I can get it. It may not have the best adjacent channel rejection but the signal is the strongest when the signal generator is set to 456 Kc.
::: The front part of the radio is what I'm having trouble with, and NOT the 456 Kc area. The radio is not converting (moving) the received frequency to 456 Kc. I can hear 570 Kc near the low end of the band and 620 Kc near the high end of the band (I live right near the brodcast antennas for these stations). That's all it does. It absolutely refuses to oscillate under any circumstances. I have checked about all I can check. All is working and not working at the same time.
::: The trimmers you are talking about are the oscillator trimmers that can only do anything, are only active, if the oscillator is working. I can put them in any position and they do nothing. They aren't shorted. They are perfectly good but not active because the oscillator is dead.
::: C-18 is brand new. It doesn't have any problems. One end is connected to the chassis and the other end is connected to a resistor. R3. I'll double check that it's also connected to the dead oscillator coil. It's not open. It just refuses to oscillate. All 11 paper and 2 electrolytic capacitors have been replaced. The positives of the electrolytic capacitors connect to the same place and the negatives connect to two different places.
::: I am getting close to removing the oscillator coil and replacing it or rewinding this one. If only I had the specs for this one. The part number on it is: 2DT200. Maybe someone has an Emerson specs book.
:::
:::Thanks,
:::
:::Dave
:::
::::Dave,
::::The oscillator has 2 trimmers in BC mode. One on the tuning cap (C-3) and the other at the rear (C-5), either of which could hamper operation if misadjusted. The one at C-3 is common to both SW and BC. Check C-18. Also, when you tested the IF, (456kHz) were you using signal levels low to moderate or high enough to blast through at any freq?
::::
::::marv
::::
:::::Marv,
::::: The resistors are the correct value. I checked them. I never replaced them. I also knew that the long black capacitor looking devices were also resistors. They are all correct. The capacitors are in the correct places. Nothing has been changed.
::::: I'll check the voltage and double check for "birdies". I think I did hear them. My huge isolation transformer is getting a lot of use on this restoration.
:::::
:::::Thanks,
:::::
:::::Dave
:::::
::::::Dave,
::::::In reading your 2 posts, I assume the set never worked and you re-capped and replaced bad resistors first. In this case, did you replace the parts just as they were originally installed, but did you also verify their placement via the schematic?
::::::
::::::marv
::::::
:::::::Radiodoc,
::::::: I just tried that and it makes absolutely no difference whatsoever.
::::::: What do I look at next?
:::::::
:::::::Thanks,
:::::::
::::::::Dave,
::::::::
::::::::The 98 volts is probably ok. If all else failed and as a shot in the dark, I would reverse the coil leads on the non-tuned winding between B+ and the oscillator "plate" and see what happens.
::::::::
::::::::Radiodoc
::::::::***************
::::::::
:::::::::Radiodoc,
::::::::: I took out the oscillator coil and checked every connection and all are good (Perfect), no opens. I checked and cleaned the band switch several times. I replaced C9 several times. When I connect 456 Kc to it from my RF signal generator, it receives that tone perfectly. It blasts!! But it wont take what's presented to it from the antenna terminals and convert that to 456 Kc. It absolutely refuses to do that under any circumstances.
::::::::: I checked all the connections and they are perfectly perfectly perfect. The resistors are all the correct values. The solder connections have been re-done and they are nice and shiny.
::::::::: I tried 3 different 6A7 tubes and none of them make any difference.
::::::::: I checked to make sure that the tuning capacitor or trimmer have any shorts on the oscillator side and there are no shorts. When the set is on and I try to adjust the oscillator screw or short the rotor with the stator on the oscillator side it makes no difference at all. All it's doing is "TRFing". The person who owns this radio MUST have the radio working immediately. I must continue working on it until it works. What do I do next? How do I convert it to a TRF receiver?
:::::::::
:::::::::Thanks,
:::::::::
:::::::::Dave
::::::::::Radiodoc,
:::::::::: B+ is 98 volts. Is that low? Shouldn't it be a little higher? I can't see any way to raise it. Filament voltage on the 6A7 is 5.3 volts.
::::::::::
::::::::::Thanks,
::::::::::
::::::::::Dave
:::::::::::Radiodoc,
::::::::::: C9 is a 100 pf capacitor. I replaced it and it made absolutely no difference.
:::::::::::
:::::::::::Dave
::::::::::::Dave,
::::::::::::
::::::::::::If all fails, walk away for a while and then come back and check carefully all the wiring around the osc circuit for correctness and good solder joints. Did you check C9 (probably a mica)or replace it. If not may try substituting another. Voltage checks on the stage may give a clue if any are off very much.
::::::::::::
::::::::::::Radiodoc
::::::::::::***********
::::::::::::
::::::::::::
:::::::::::::Hello All,
::::::::::::: I have checked everything and the oscillator absolutely refuses to work. All paper and filter capacitors have been replaced. No part of the oscillator coil is open. The resistors are good. I tried a few 6A7s and it still wont work. What to I look at next?
::::::::::::: This is an AC/DC set. There's not that much there.
:::::::::::::
:::::::::::::Thanks,
:::::::::::::
:::::::::::::Dave
How difficult would it be to re-wind the old oscillator coil? I think it would be pretty difficult to do.
Thanks,
Dave
:Edd,
: The person who owns the radio finally ordered a universal BC oscillator coil and I hooked it up and "like magic" the radio is working.
: Thanks a lot for everyone's help.
:Dave
::
::
::
::
::After reviewing your last postings info:
::My fustus “querstion” was if the radio operated in some degree of receiving stations ? via a tunable superheterodyne action / mode prior to the mass recapping of the unit ?
::
::
::
::Can we assume that C9..100 mmfd was ok and not even messed with ?
::Is cathode resistor R2 wired up ok and at its ~350 ohm value ?
::As well as the grid resistor of R1 ….50k wired properly and at its value ?
::The last item which I am sure that you did get involved with was the cathode bypass Condenser C7….05 ufd and it is OK and was reinstalled to the correct terminals…right…as that is also as critical as the 3 companion items.
::
::
::
::Looks as if the oscillator coil is on the larger ½ to ¾ in coil form and and a Litz wound unit in a tight layer…rather than the old style of enameled wire wound the full length of a long coil form. Plus, you seem to attest of its wirings continuity integrity as well as the adjunct tuning cap and its trimmer caps not being shorted out or dragging plates. Plus the additional reverting of one of the windings for a proper feed back phase check.
::Also with your BEE und KAY, you should be able to couple its input into the first grid of the mixer and at the proper injection of CW RF level, be able to swing its dial thru the 1005-2195 khc range and tune thru your stronger receptive stations in the area, with the two “TRF” stations being the powerhouses, BUT with the necessity of having to manually tune the tuning condenser in order to optimize the RF section being in resonance with them, when trying for weaker stations in bringing up received reception level..
::
::
::
::To further ease your mind about the radios oscillator sections L-C combinations , you could go to the juncture of C9 and R1 and couple in CW RF via a series / isolative ~100 pf cap and go to the same junction and tack on an anode of a 1N34 / 60 / 64 / 270 GERMANIUM diode and at its cathodes end , take a .001 cap for bypassing to ground and then meter the cathodes output via a VTVM.
::
::
::(N0…1N 914’s/4148’s/1N400oseries for this application)(Radio Shack stocks them in case you don’t have one from an oooold generation AM transistor radio chassis or from the building of a crystal set.)
::
::
::
::Then if you will power up the BEE und KAY and place in its CW mode and set the Emerson…(No power required....as this testing will be passive)…to the 1/3 lower end of the dial 700 kc ish (tuning cap ~ ¾ meshed)
::Then you tune the B & K in the ~1000-1400 range and see if the co-joined parasitic tuned oscillators circuit doesn’t give you a rising / declining reading as resonance was scanned across.
::Then, hop the radios tuning up to the higher third of the band (tuning cap ~ 1/4 meshed) and test for a like reading of a viable resonant circuit pair working at that
::frequency also.
::Thereby you have merely temp- rigged up a “po boys” grid dipper to interpret the presence of a functioning / resonating effect by the osc sections variable L-C pair and it having some degree of “Q”.
::
::
::The other alternative being that recurrent sweep Eico 460 Scope / Kluge of yours, so I think that with the former detected and metered RF , you would be much better off.
::
::
::
::Addenda:
::Noticed your new readings just at this posting time, and the bucolic local osc grid voltages reading. And have you confirmed that there is even any level oscillation by the taking of a portable xstr radios ferri-loop and placing it atop the osc coil winding and tune it off station just onto the very edge / sideband of a weaker ~1400-1740 kc AM station and then run the operating radio's tuning condenser across the bottom half of the AM band to see if even a weak heterodyning / birdie is heard on the xstr radio.
::
::Standing by for feed back
::
::
::73's de Edd
::
::
::
::
::
::
::
::
::
::
:::Marv and all,
:::
::: Here are the voltage readings on the 6A7 tube.
:::
:::Pins 1 & 7: 6.8 volts AC (Filament)
:::Pin 2: 107.5 v DC (Plate)
:::Pin 3: 43.5 volts DC (G3 and G5)
:::Pin 4: 106.7 volts (G2)
:::Pin 5: 2.2 V DC (G1)
:::Pin 6: 2.647 volts DC (Cathode)
:::Cap: -.361 v DC (G4)
:::
:::These seem like pretty healthy voltages to me. I don't see anything wrong there. The IF transformer is connecting B+ to the plate and the Oscillator coil is connecting B+ to to pin 4. So neither coil is open.
:::
:::I did notice that C17 was missing. I put it back and it might have made an improvement but not with the oscillator.
:::
:::Please if anyone has anymore ideas before I "attack" (very closely examine) the oscillator coil, please help.
:::
:::Thanks,
:::
:::Dave
:::
::::Marv,
:::: My RF signal generator modulates a 400 Hz tone on the 456 Kc carrier frequency when it's set to 456 Kc. The part of the radio that the signal generator is connected to is tune to exactly tuned to 456 Kc. It can receive 456 Kc and only 456 Kc. That "station" is received and I can blast the 400 Hz tone through the speaker of the radio. If I change the RF signal generator to another frequency, then no 400 Hz tone is heard. It is as perfectly aligned as I can get it. It may not have the best adjacent channel rejection but the signal is the strongest when the signal generator is set to 456 Kc.
:::: The front part of the radio is what I'm having trouble with, and NOT the 456 Kc area. The radio is not converting (moving) the received frequency to 456 Kc. I can hear 570 Kc near the low end of the band and 620 Kc near the high end of the band (I live right near the brodcast antennas for these stations). That's all it does. It absolutely refuses to oscillate under any circumstances. I have checked about all I can check. All is working and not working at the same time.
:::: The trimmers you are talking about are the oscillator trimmers that can only do anything, are only active, if the oscillator is working. I can put them in any position and they do nothing. They aren't shorted. They are perfectly good but not active because the oscillator is dead.
:::: C-18 is brand new. It doesn't have any problems. One end is connected to the chassis and the other end is connected to a resistor. R3. I'll double check that it's also connected to the dead oscillator coil. It's not open. It just refuses to oscillate. All 11 paper and 2 electrolytic capacitors have been replaced. The positives of the electrolytic capacitors connect to the same place and the negatives connect to two different places.
:::: I am getting close to removing the oscillator coil and replacing it or rewinding this one. If only I had the specs for this one. The part number on it is: 2DT200. Maybe someone has an Emerson specs book.
::::
::::Thanks,
::::
::::Dave
::::
:::::Dave,
:::::The oscillator has 2 trimmers in BC mode. One on the tuning cap (C-3) and the other at the rear (C-5), either of which could hamper operation if misadjusted. The one at C-3 is common to both SW and BC. Check C-18. Also, when you tested the IF, (456kHz) were you using signal levels low to moderate or high enough to blast through at any freq?
:::::
:::::marv
:::::
::::::Marv,
:::::: The resistors are the correct value. I checked them. I never replaced them. I also knew that the long black capacitor looking devices were also resistors. They are all correct. The capacitors are in the correct places. Nothing has been changed.
:::::: I'll check the voltage and double check for "birdies". I think I did hear them. My huge isolation transformer is getting a lot of use on this restoration.
::::::
::::::Thanks,
::::::
::::::Dave
::::::
:::::::Dave,
:::::::In reading your 2 posts, I assume the set never worked and you re-capped and replaced bad resistors first. In this case, did you replace the parts just as they were originally installed, but did you also verify their placement via the schematic?
:::::::
:::::::marv
:::::::
::::::::Radiodoc,
:::::::: I just tried that and it makes absolutely no difference whatsoever.
:::::::: What do I look at next?
::::::::
::::::::Thanks,
::::::::
:::::::::Dave,
:::::::::
:::::::::The 98 volts is probably ok. If all else failed and as a shot in the dark, I would reverse the coil leads on the non-tuned winding between B+ and the oscillator "plate" and see what happens.
:::::::::
:::::::::Radiodoc
:::::::::***************
:::::::::
::::::::::Radiodoc,
:::::::::: I took out the oscillator coil and checked every connection and all are good (Perfect), no opens. I checked and cleaned the band switch several times. I replaced C9 several times. When I connect 456 Kc to it from my RF signal generator, it receives that tone perfectly. It blasts!! But it wont take what's presented to it from the antenna terminals and convert that to 456 Kc. It absolutely refuses to do that under any circumstances.
:::::::::: I checked all the connections and they are perfectly perfectly perfect. The resistors are all the correct values. The solder connections have been re-done and they are nice and shiny.
:::::::::: I tried 3 different 6A7 tubes and none of them make any difference.
:::::::::: I checked to make sure that the tuning capacitor or trimmer have any shorts on the oscillator side and there are no shorts. When the set is on and I try to adjust the oscillator screw or short the rotor with the stator on the oscillator side it makes no difference at all. All it's doing is "TRFing". The person who owns this radio MUST have the radio working immediately. I must continue working on it until it works. What do I do next? How do I convert it to a TRF receiver?
::::::::::
::::::::::Thanks,
::::::::::
::::::::::Dave
:::::::::::Radiodoc,
::::::::::: B+ is 98 volts. Is that low? Shouldn't it be a little higher? I can't see any way to raise it. Filament voltage on the 6A7 is 5.3 volts.
:::::::::::
:::::::::::Thanks,
:::::::::::
:::::::::::Dave
::::::::::::Radiodoc,
:::::::::::: C9 is a 100 pf capacitor. I replaced it and it made absolutely no difference.
::::::::::::
::::::::::::Dave
:::::::::::::Dave,
:::::::::::::
:::::::::::::If all fails, walk away for a while and then come back and check carefully all the wiring around the osc circuit for correctness and good solder joints. Did you check C9 (probably a mica)or replace it. If not may try substituting another. Voltage checks on the stage may give a clue if any are off very much.
:::::::::::::
:::::::::::::Radiodoc
:::::::::::::***********
:::::::::::::
:::::::::::::
::::::::::::::Hello All,
:::::::::::::: I have checked everything and the oscillator absolutely refuses to work. All paper and filter capacitors have been replaced. No part of the oscillator coil is open. The resistors are good. I tried a few 6A7s and it still wont work. What to I look at next?
:::::::::::::: This is an AC/DC set. There's not that much there.
::::::::::::::
::::::::::::::Thanks,
::::::::::::::
::::::::::::::Dave
This is not related to this posting. A while back you posted that you needed documentation for the B&K 415. Re-check that posting. If you don't need the info let me know and I'll fade into the background.
MRO
Yes, I'd like to know how it works. I still have the 415.
Thanks,
Dave
:MR Dave,
:
:This is not related to this posting. A while back you posted that you needed documentation for the B&K 415. Re-check that posting. If you don't need the info let me know and I'll fade into the background.
:
:MRO
Contact me at the22troops@yahoo.com
MRO