Thanks,
Dave
Don't have the schematic but here goes... You need a resistor from plate of the 6BJ8 to B+. Use 22K. Take the signal off plate through a .01 mf cap.
6BJ8 has an amplification factor of 20 so should have a cathode resistor. Use 1K here bypassed by a 10 mf electrolytic. Positive toward cathode. Will work with cathode grounded but nay have some distortion.
This will increase gain by nearly a factor of 20.
Norm
:Hello All,
: I am puzzled by the strange FM output triode connections. The sound comes from the cathode (cathode follower output? no amplification?). The tube doesn't seem to be biased on at all. I'd like to change the circuit so that the triode section of the 6BJ8 has either cathode or fixed bias and the output comes from the anode through a capacitor. What value resistor should I use or can I connect the cathode directly to the chassis (fixed bias). The schematic shows a dropping resistor between the final capacitor and the plate of the triode section, but there is no such resistor in the unit. The schematic is inside the bottom. There is also, no output control. That was eliminated and it looks like it was done at the factory. I would like the triode to act as a pre-amp to boost the output signal higher than what comes through the MPX output jack.
: I'm going to try the fixed bias first. All I want to change is the way the triode is operating. I don't wish to make any other changes. I want this to have a line or headphone level output. If anyone knows what the values should be, please let me know. I should know this but never learned it. It's about time I did.
:
:Thanks,
:
:Dave
:
What do I look at next? The tube tests good. I'll keep trying to get a stronger signal out of it.
Thanks,
Dave
:Hi Dave
:
: Don't have the schematic but here goes... You need a resistor from plate of the 6BJ8 to B+. Use 22K. Take the signal off plate through a .01 mf cap.
:
: 6BJ8 has an amplification factor of 20 so should have a cathode resistor. Use 1K here bypassed by a 10 mf electrolytic. Positive toward cathode. Will work with cathode grounded but nay have some distortion.
:
: This will increase gain by nearly a factor of 20.
:
:Norm
:
:
::Hello All,
:: I am puzzled by the strange FM output triode connections. The sound comes from the cathode (cathode follower output? no amplification?). The tube doesn't seem to be biased on at all. I'd like to change the circuit so that the triode section of the 6BJ8 has either cathode or fixed bias and the output comes from the anode through a capacitor. What value resistor should I use or can I connect the cathode directly to the chassis (fixed bias). The schematic shows a dropping resistor between the final capacitor and the plate of the triode section, but there is no such resistor in the unit. The schematic is inside the bottom. There is also, no output control. That was eliminated and it looks like it was done at the factory. I would like the triode to act as a pre-amp to boost the output signal higher than what comes through the MPX output jack.
:: I'm going to try the fixed bias first. All I want to change is the way the triode is operating. I don't wish to make any other changes. I want this to have a line or headphone level output. If anyone knows what the values should be, please let me know. I should know this but never learned it. It's about time I did.
::
::Thanks,
::
::Dave
::
:
:
The grid may be going too negative? There should already be a grid resistor in your original circuit. If not connect a 470K - 1 meg to ground.
Is the grid capacity coupled? Should be and with a grid resistor added there will be gain.
Norm
:Hello Norm,
: I tried what you said and the signal through the .01 mf capacitor is very weak compared to the input at the grid. There are resistors in the power supply. It's half wave with three resistors and 3 filter capacitors. The plate of the 6BJ8 gets the lowest voltage, which is about 110. The signal going into the amplifier is louder than what's coming out. It's very odd. The tube refuses to turn on. No other wires are attached to it. From the cathode I have the 1 k ohm resistor with the 10 mf capacitor across it. The positive lead of the capacitor is connected to the cathode. The input signal is coming through a disc capacitor to the grid. I can hear signal on both ends of the capacitor. Does there need to be a grid resistor? This is very strange. I have no idea what's going on. It should work but it doesn't.
:
:What do I look at next? The tube tests good. I'll keep trying to get a stronger signal out of it.
:
:Thanks,
:
:Dave
::Hi Dave
::
:: Don't have the schematic but here goes... You need a resistor from plate of the 6BJ8 to B+. Use 22K. Take the signal off plate through a .01 mf cap.
::
:: 6BJ8 has an amplification factor of 20 so should have a cathode resistor. Use 1K here bypassed by a 10 mf electrolytic. Positive toward cathode. Will work with cathode grounded but nay have some distortion.
::
:: This will increase gain by nearly a factor of 20.
::
::Norm
::
::
:::Hello All,
::: I am puzzled by the strange FM output triode connections. The sound comes from the cathode (cathode follower output? no amplification?). The tube doesn't seem to be biased on at all. I'd like to change the circuit so that the triode section of the 6BJ8 has either cathode or fixed bias and the output comes from the anode through a capacitor. What value resistor should I use or can I connect the cathode directly to the chassis (fixed bias). The schematic shows a dropping resistor between the final capacitor and the plate of the triode section, but there is no such resistor in the unit. The schematic is inside the bottom. There is also, no output control. That was eliminated and it looks like it was done at the factory. I would like the triode to act as a pre-amp to boost the output signal higher than what comes through the MPX output jack.
::: I'm going to try the fixed bias first. All I want to change is the way the triode is operating. I don't wish to make any other changes. I want this to have a line or headphone level output. If anyone knows what the values should be, please let me know. I should know this but never learned it. It's about time I did.
:::
:::Thanks,
:::
:::Dave
:::
::
::
:
:
Thanks,
Dave
:Dave
:
: The grid may be going too negative? There should already be a grid resistor in your original circuit. If not connect a 470K - 1 meg to ground.
:
: Is the grid capacity coupled? Should be and with a grid resistor added there will be gain.
:
:Norm
:
::Hello Norm,
:: I tried what you said and the signal through the .01 mf capacitor is very weak compared to the input at the grid. There are resistors in the power supply. It's half wave with three resistors and 3 filter capacitors. The plate of the 6BJ8 gets the lowest voltage, which is about 110. The signal going into the amplifier is louder than what's coming out. It's very odd. The tube refuses to turn on. No other wires are attached to it. From the cathode I have the 1 k ohm resistor with the 10 mf capacitor across it. The positive lead of the capacitor is connected to the cathode. The input signal is coming through a disc capacitor to the grid. I can hear signal on both ends of the capacitor. Does there need to be a grid resistor? This is very strange. I have no idea what's going on. It should work but it doesn't.
::
::What do I look at next? The tube tests good. I'll keep trying to get a stronger signal out of it.
::
::Thanks,
::
::Dave
:::Hi Dave
:::
::: Don't have the schematic but here goes... You need a resistor from plate of the 6BJ8 to B+. Use 22K. Take the signal off plate through a .01 mf cap.
:::
::: 6BJ8 has an amplification factor of 20 so should have a cathode resistor. Use 1K here bypassed by a 10 mf electrolytic. Positive toward cathode. Will work with cathode grounded but nay have some distortion.
:::
::: This will increase gain by nearly a factor of 20.
:::
:::Norm
:::
:::
::::Hello All,
:::: I am puzzled by the strange FM output triode connections. The sound comes from the cathode (cathode follower output? no amplification?). The tube doesn't seem to be biased on at all. I'd like to change the circuit so that the triode section of the 6BJ8 has either cathode or fixed bias and the output comes from the anode through a capacitor. What value resistor should I use or can I connect the cathode directly to the chassis (fixed bias). The schematic shows a dropping resistor between the final capacitor and the plate of the triode section, but there is no such resistor in the unit. The schematic is inside the bottom. There is also, no output control. That was eliminated and it looks like it was done at the factory. I would like the triode to act as a pre-amp to boost the output signal higher than what comes through the MPX output jack.
:::: I'm going to try the fixed bias first. All I want to change is the way the triode is operating. I don't wish to make any other changes. I want this to have a line or headphone level output. If anyone knows what the values should be, please let me know. I should know this but never learned it. It's about time I did.
::::
::::Thanks,
::::
::::Dave
::::
:::
:::
::
::
:
:
Thanks,
Dave
:Norm,
: I had added a 470K because someone removed the volume control (looks like it was done at the factory). Now I've just snipped it out. I'll get another one. There is a resistor feeding a capacitor and the capacitor is connected to the grid.
: Is it normal to have sound coming through the cathode that's louder than through the anode (plate)? I'll try putting back the grid resistor and let you know what happens.
:
:Thanks,
:
:Dave
::Dave
::
:: The grid may be going too negative? There should already be a grid resistor in your original circuit. If not connect a 470K - 1 meg to ground.
::
:: Is the grid capacity coupled? Should be and with a grid resistor added there will be gain.
::
::Norm
::
:::Hello Norm,
::: I tried what you said and the signal through the .01 mf capacitor is very weak compared to the input at the grid. There are resistors in the power supply. It's half wave with three resistors and 3 filter capacitors. The plate of the 6BJ8 gets the lowest voltage, which is about 110. The signal going into the amplifier is louder than what's coming out. It's very odd. The tube refuses to turn on. No other wires are attached to it. From the cathode I have the 1 k ohm resistor with the 10 mf capacitor across it. The positive lead of the capacitor is connected to the cathode. The input signal is coming through a disc capacitor to the grid. I can hear signal on both ends of the capacitor. Does there need to be a grid resistor? This is very strange. I have no idea what's going on. It should work but it doesn't.
:::
:::What do I look at next? The tube tests good. I'll keep trying to get a stronger signal out of it.
:::
:::Thanks,
:::
:::Dave
::::Hi Dave
::::
:::: Don't have the schematic but here goes... You need a resistor from plate of the 6BJ8 to B+. Use 22K. Take the signal off plate through a .01 mf cap.
::::
:::: 6BJ8 has an amplification factor of 20 so should have a cathode resistor. Use 1K here bypassed by a 10 mf electrolytic. Positive toward cathode. Will work with cathode grounded but nay have some distortion.
::::
:::: This will increase gain by nearly a factor of 20.
::::
::::Norm
::::
::::
:::::Hello All,
::::: I am puzzled by the strange FM output triode connections. The sound comes from the cathode (cathode follower output? no amplification?). The tube doesn't seem to be biased on at all. I'd like to change the circuit so that the triode section of the 6BJ8 has either cathode or fixed bias and the output comes from the anode through a capacitor. What value resistor should I use or can I connect the cathode directly to the chassis (fixed bias). The schematic shows a dropping resistor between the final capacitor and the plate of the triode section, but there is no such resistor in the unit. The schematic is inside the bottom. There is also, no output control. That was eliminated and it looks like it was done at the factory. I would like the triode to act as a pre-amp to boost the output signal higher than what comes through the MPX output jack.
::::: I'm going to try the fixed bias first. All I want to change is the way the triode is operating. I don't wish to make any other changes. I want this to have a line or headphone level output. If anyone knows what the values should be, please let me know. I should know this but never learned it. It's about time I did.
:::::
:::::Thanks,
:::::
:::::Dave
:::::
::::
::::
:::
:::
::
::
:
:
Must be something obvious here.
Grid is pin #8. This one should have a 470K resistor to ground. A signal needs to be fed in through a cap, .01 mf or similar.
Cathode is pin #9. You have a 1K resistor from this pin to ground. It's bypassed with a 10mf cap. There should be no signal on this pin.
Pin #7 is plate. It should have a resistor to B+, 22K or similar. You can take output from this pin through a cap, .01 mf etc.
Should be no other connections on these pins. Pin #7 may have gone directly to B+ before?
Norm
:Norm,
: Adding the grid resistor decreased the output so that now it's barely audible. It's still there but it's very very quiet. What should I do next?
:
:Thanks,
:
:Dave
::Norm,
:: I had added a 470K because someone removed the volume control (looks like it was done at the factory). Now I've just snipped it out. I'll get another one. There is a resistor feeding a capacitor and the capacitor is connected to the grid.
:: Is it normal to have sound coming through the cathode that's louder than through the anode (plate)? I'll try putting back the grid resistor and let you know what happens.
::
::Thanks,
::
::Dave
:::Dave
:::
::: The grid may be going too negative? There should already be a grid resistor in your original circuit. If not connect a 470K - 1 meg to ground.
:::
::: Is the grid capacity coupled? Should be and with a grid resistor added there will be gain.
:::
:::Norm
:::
::::Hello Norm,
:::: I tried what you said and the signal through the .01 mf capacitor is very weak compared to the input at the grid. There are resistors in the power supply. It's half wave with three resistors and 3 filter capacitors. The plate of the 6BJ8 gets the lowest voltage, which is about 110. The signal going into the amplifier is louder than what's coming out. It's very odd. The tube refuses to turn on. No other wires are attached to it. From the cathode I have the 1 k ohm resistor with the 10 mf capacitor across it. The positive lead of the capacitor is connected to the cathode. The input signal is coming through a disc capacitor to the grid. I can hear signal on both ends of the capacitor. Does there need to be a grid resistor? This is very strange. I have no idea what's going on. It should work but it doesn't.
::::
::::What do I look at next? The tube tests good. I'll keep trying to get a stronger signal out of it.
::::
::::Thanks,
::::
::::Dave
:::::Hi Dave
:::::
::::: Don't have the schematic but here goes... You need a resistor from plate of the 6BJ8 to B+. Use 22K. Take the signal off plate through a .01 mf cap.
:::::
::::: 6BJ8 has an amplification factor of 20 so should have a cathode resistor. Use 1K here bypassed by a 10 mf electrolytic. Positive toward cathode. Will work with cathode grounded but nay have some distortion.
:::::
::::: This will increase gain by nearly a factor of 20.
:::::
:::::Norm
:::::
:::::
::::::Hello All,
:::::: I am puzzled by the strange FM output triode connections. The sound comes from the cathode (cathode follower output? no amplification?). The tube doesn't seem to be biased on at all. I'd like to change the circuit so that the triode section of the 6BJ8 has either cathode or fixed bias and the output comes from the anode through a capacitor. What value resistor should I use or can I connect the cathode directly to the chassis (fixed bias). The schematic shows a dropping resistor between the final capacitor and the plate of the triode section, but there is no such resistor in the unit. The schematic is inside the bottom. There is also, no output control. That was eliminated and it looks like it was done at the factory. I would like the triode to act as a pre-amp to boost the output signal higher than what comes through the MPX output jack.
:::::: I'm going to try the fixed bias first. All I want to change is the way the triode is operating. I don't wish to make any other changes. I want this to have a line or headphone level output. If anyone knows what the values should be, please let me know. I should know this but never learned it. It's about time I did.
::::::
::::::Thanks,
::::::
::::::Dave
::::::
:::::
:::::
::::
::::
:::
:::
::
::
:
:
Thanks,
Dave
:Dave
:
: Must be something obvious here.
:
: Grid is pin #8. This one should have a 470K resistor to ground. A signal needs to be fed in through a cap, .01 mf or similar.
:
: Cathode is pin #9. You have a 1K resistor from this pin to ground. It's bypassed with a 10mf cap. There should be no signal on this pin.
:
: Pin #7 is plate. It should have a resistor to B+, 22K or similar. You can take output from this pin through a cap, .01 mf etc.
:
: Should be no other connections on these pins. Pin #7 may have gone directly to B+ before?
:
:Norm
:
::Norm,
:: Adding the grid resistor decreased the output so that now it's barely audible. It's still there but it's very very quiet. What should I do next?
::
::Thanks,
::
::Dave
:::Norm,
::: I had added a 470K because someone removed the volume control (looks like it was done at the factory). Now I've just snipped it out. I'll get another one. There is a resistor feeding a capacitor and the capacitor is connected to the grid.
::: Is it normal to have sound coming through the cathode that's louder than through the anode (plate)? I'll try putting back the grid resistor and let you know what happens.
:::
:::Thanks,
:::
:::Dave
::::Dave
::::
:::: The grid may be going too negative? There should already be a grid resistor in your original circuit. If not connect a 470K - 1 meg to ground.
::::
:::: Is the grid capacity coupled? Should be and with a grid resistor added there will be gain.
::::
::::Norm
::::
:::::Hello Norm,
::::: I tried what you said and the signal through the .01 mf capacitor is very weak compared to the input at the grid. There are resistors in the power supply. It's half wave with three resistors and 3 filter capacitors. The plate of the 6BJ8 gets the lowest voltage, which is about 110. The signal going into the amplifier is louder than what's coming out. It's very odd. The tube refuses to turn on. No other wires are attached to it. From the cathode I have the 1 k ohm resistor with the 10 mf capacitor across it. The positive lead of the capacitor is connected to the cathode. The input signal is coming through a disc capacitor to the grid. I can hear signal on both ends of the capacitor. Does there need to be a grid resistor? This is very strange. I have no idea what's going on. It should work but it doesn't.
:::::
:::::What do I look at next? The tube tests good. I'll keep trying to get a stronger signal out of it.
:::::
:::::Thanks,
:::::
:::::Dave
::::::Hi Dave
::::::
:::::: Don't have the schematic but here goes... You need a resistor from plate of the 6BJ8 to B+. Use 22K. Take the signal off plate through a .01 mf cap.
::::::
:::::: 6BJ8 has an amplification factor of 20 so should have a cathode resistor. Use 1K here bypassed by a 10 mf electrolytic. Positive toward cathode. Will work with cathode grounded but nay have some distortion.
::::::
:::::: This will increase gain by nearly a factor of 20.
::::::
::::::Norm
::::::
::::::
:::::::Hello All,
::::::: I am puzzled by the strange FM output triode connections. The sound comes from the cathode (cathode follower output? no amplification?). The tube doesn't seem to be biased on at all. I'd like to change the circuit so that the triode section of the 6BJ8 has either cathode or fixed bias and the output comes from the anode through a capacitor. What value resistor should I use or can I connect the cathode directly to the chassis (fixed bias). The schematic shows a dropping resistor between the final capacitor and the plate of the triode section, but there is no such resistor in the unit. The schematic is inside the bottom. There is also, no output control. That was eliminated and it looks like it was done at the factory. I would like the triode to act as a pre-amp to boost the output signal higher than what comes through the MPX output jack.
::::::: I'm going to try the fixed bias first. All I want to change is the way the triode is operating. I don't wish to make any other changes. I want this to have a line or headphone level output. If anyone knows what the values should be, please let me know. I should know this but never learned it. It's about time I did.
:::::::
:::::::Thanks,
:::::::
:::::::Dave
:::::::
::::::
::::::
:::::
:::::
::::
::::
:::
:::
::
::
:
:
You do not want B+ connected directly to the plate. It should go through a 22K or 33K resistor. That's the problem.
You have some signal on the cathode because plate is held at B+. You are forcing the tube.
Norm
:Norm,
: Yes this is how pin 8 is. .01mf capacitor connecting signal to the grid. 470K ohm resistor to ground. Pin 9 I have as you stated, however, no matter what I do, there is a signal coming from the cathode. Maybe interference from the two diodes? There are absolutely no other wires connected to the cathode.
: Pin 7, there are B+++ (170), B++, and B+ (110). voltages. B+ is connected directly to the plate. I will add a 22K ohm resistor and let you know what happens. The schematic shows one, but there is no 22K ohm resistor. I think it shows a 33K ohm resistor. Does this really affect the gain?
:
:Thanks,
:
:Dave
::Dave
::
:: Must be something obvious here.
::
:: Grid is pin #8. This one should have a 470K resistor to ground. A signal needs to be fed in through a cap, .01 mf or similar.
::
:: Cathode is pin #9. You have a 1K resistor from this pin to ground. It's bypassed with a 10mf cap. There should be no signal on this pin.
::
:: Pin #7 is plate. It should have a resistor to B+, 22K or similar. You can take output from this pin through a cap, .01 mf etc.
::
:: Should be no other connections on these pins. Pin #7 may have gone directly to B+ before?
::
::Norm
::
:::Norm,
::: Adding the grid resistor decreased the output so that now it's barely audible. It's still there but it's very very quiet. What should I do next?
:::
:::Thanks,
:::
:::Dave
::::Norm,
:::: I had added a 470K because someone removed the volume control (looks like it was done at the factory). Now I've just snipped it out. I'll get another one. There is a resistor feeding a capacitor and the capacitor is connected to the grid.
:::: Is it normal to have sound coming through the cathode that's louder than through the anode (plate)? I'll try putting back the grid resistor and let you know what happens.
::::
::::Thanks,
::::
::::Dave
:::::Dave
:::::
::::: The grid may be going too negative? There should already be a grid resistor in your original circuit. If not connect a 470K - 1 meg to ground.
:::::
::::: Is the grid capacity coupled? Should be and with a grid resistor added there will be gain.
:::::
:::::Norm
:::::
::::::Hello Norm,
:::::: I tried what you said and the signal through the .01 mf capacitor is very weak compared to the input at the grid. There are resistors in the power supply. It's half wave with three resistors and 3 filter capacitors. The plate of the 6BJ8 gets the lowest voltage, which is about 110. The signal going into the amplifier is louder than what's coming out. It's very odd. The tube refuses to turn on. No other wires are attached to it. From the cathode I have the 1 k ohm resistor with the 10 mf capacitor across it. The positive lead of the capacitor is connected to the cathode. The input signal is coming through a disc capacitor to the grid. I can hear signal on both ends of the capacitor. Does there need to be a grid resistor? This is very strange. I have no idea what's going on. It should work but it doesn't.
::::::
::::::What do I look at next? The tube tests good. I'll keep trying to get a stronger signal out of it.
::::::
::::::Thanks,
::::::
::::::Dave
:::::::Hi Dave
:::::::
::::::: Don't have the schematic but here goes... You need a resistor from plate of the 6BJ8 to B+. Use 22K. Take the signal off plate through a .01 mf cap.
:::::::
::::::: 6BJ8 has an amplification factor of 20 so should have a cathode resistor. Use 1K here bypassed by a 10 mf electrolytic. Positive toward cathode. Will work with cathode grounded but nay have some distortion.
:::::::
::::::: This will increase gain by nearly a factor of 20.
:::::::
:::::::Norm
:::::::
:::::::
::::::::Hello All,
:::::::: I am puzzled by the strange FM output triode connections. The sound comes from the cathode (cathode follower output? no amplification?). The tube doesn't seem to be biased on at all. I'd like to change the circuit so that the triode section of the 6BJ8 has either cathode or fixed bias and the output comes from the anode through a capacitor. What value resistor should I use or can I connect the cathode directly to the chassis (fixed bias). The schematic shows a dropping resistor between the final capacitor and the plate of the triode section, but there is no such resistor in the unit. The schematic is inside the bottom. There is also, no output control. That was eliminated and it looks like it was done at the factory. I would like the triode to act as a pre-amp to boost the output signal higher than what comes through the MPX output jack.
:::::::: I'm going to try the fixed bias first. All I want to change is the way the triode is operating. I don't wish to make any other changes. I want this to have a line or headphone level output. If anyone knows what the values should be, please let me know. I should know this but never learned it. It's about time I did.
::::::::
::::::::Thanks,
::::::::
::::::::Dave
::::::::
:::::::
:::::::
::::::
::::::
:::::
:::::
::::
::::
:::
:::
::
::
:
:
Thanks,
Dave
:Dave
:
: You do not want B+ connected directly to the plate. It should go through a 22K or 33K resistor. That's the problem.
:
: You have some signal on the cathode because plate is held at B+. You are forcing the tube.
:
:Norm
:
:
::Norm,
:: Yes this is how pin 8 is. .01mf capacitor connecting signal to the grid. 470K ohm resistor to ground. Pin 9 I have as you stated, however, no matter what I do, there is a signal coming from the cathode. Maybe interference from the two diodes? There are absolutely no other wires connected to the cathode.
:: Pin 7, there are B+++ (170), B++, and B+ (110). voltages. B+ is connected directly to the plate. I will add a 22K ohm resistor and let you know what happens. The schematic shows one, but there is no 22K ohm resistor. I think it shows a 33K ohm resistor. Does this really affect the gain?
::
::Thanks,
::
::Dave
:::Dave
:::
::: Must be something obvious here.
:::
::: Grid is pin #8. This one should have a 470K resistor to ground. A signal needs to be fed in through a cap, .01 mf or similar.
:::
::: Cathode is pin #9. You have a 1K resistor from this pin to ground. It's bypassed with a 10mf cap. There should be no signal on this pin.
:::
::: Pin #7 is plate. It should have a resistor to B+, 22K or similar. You can take output from this pin through a cap, .01 mf etc.
:::
::: Should be no other connections on these pins. Pin #7 may have gone directly to B+ before?
:::
:::Norm
:::
::::Norm,
:::: Adding the grid resistor decreased the output so that now it's barely audible. It's still there but it's very very quiet. What should I do next?
::::
::::Thanks,
::::
::::Dave
:::::Norm,
::::: I had added a 470K because someone removed the volume control (looks like it was done at the factory). Now I've just snipped it out. I'll get another one. There is a resistor feeding a capacitor and the capacitor is connected to the grid.
::::: Is it normal to have sound coming through the cathode that's louder than through the anode (plate)? I'll try putting back the grid resistor and let you know what happens.
:::::
:::::Thanks,
:::::
:::::Dave
::::::Dave
::::::
:::::: The grid may be going too negative? There should already be a grid resistor in your original circuit. If not connect a 470K - 1 meg to ground.
::::::
:::::: Is the grid capacity coupled? Should be and with a grid resistor added there will be gain.
::::::
::::::Norm
::::::
:::::::Hello Norm,
::::::: I tried what you said and the signal through the .01 mf capacitor is very weak compared to the input at the grid. There are resistors in the power supply. It's half wave with three resistors and 3 filter capacitors. The plate of the 6BJ8 gets the lowest voltage, which is about 110. The signal going into the amplifier is louder than what's coming out. It's very odd. The tube refuses to turn on. No other wires are attached to it. From the cathode I have the 1 k ohm resistor with the 10 mf capacitor across it. The positive lead of the capacitor is connected to the cathode. The input signal is coming through a disc capacitor to the grid. I can hear signal on both ends of the capacitor. Does there need to be a grid resistor? This is very strange. I have no idea what's going on. It should work but it doesn't.
:::::::
:::::::What do I look at next? The tube tests good. I'll keep trying to get a stronger signal out of it.
:::::::
:::::::Thanks,
:::::::
:::::::Dave
::::::::Hi Dave
::::::::
:::::::: Don't have the schematic but here goes... You need a resistor from plate of the 6BJ8 to B+. Use 22K. Take the signal off plate through a .01 mf cap.
::::::::
:::::::: 6BJ8 has an amplification factor of 20 so should have a cathode resistor. Use 1K here bypassed by a 10 mf electrolytic. Positive toward cathode. Will work with cathode grounded but nay have some distortion.
::::::::
:::::::: This will increase gain by nearly a factor of 20.
::::::::
::::::::Norm
::::::::
::::::::
:::::::::Hello All,
::::::::: I am puzzled by the strange FM output triode connections. The sound comes from the cathode (cathode follower output? no amplification?). The tube doesn't seem to be biased on at all. I'd like to change the circuit so that the triode section of the 6BJ8 has either cathode or fixed bias and the output comes from the anode through a capacitor. What value resistor should I use or can I connect the cathode directly to the chassis (fixed bias). The schematic shows a dropping resistor between the final capacitor and the plate of the triode section, but there is no such resistor in the unit. The schematic is inside the bottom. There is also, no output control. That was eliminated and it looks like it was done at the factory. I would like the triode to act as a pre-amp to boost the output signal higher than what comes through the MPX output jack.
::::::::: I'm going to try the fixed bias first. All I want to change is the way the triode is operating. I don't wish to make any other changes. I want this to have a line or headphone level output. If anyone knows what the values should be, please let me know. I should know this but never learned it. It's about time I did.
:::::::::
:::::::::Thanks,
:::::::::
:::::::::Dave
:::::::::
::::::::
::::::::
:::::::
:::::::
::::::
::::::
:::::
:::::
::::
::::
:::
:::
::
::
:
:
Thanks Very Very Much,
Dave
Another problem, the tuning eye isn't moving. This is a different topic. I'll have to take a picture of the schematic because I can only find the 443 online, which is different.
:Norm,
: What does "forcing the tube" mean?
:
:Thanks,
:
:Dave
::Dave
::
:: You do not want B+ connected directly to the plate. It should go through a 22K or 33K resistor. That's the problem.
::
:: You have some signal on the cathode because plate is held at B+. You are forcing the tube.
::
::Norm
::
::
:::Norm,
::: Yes this is how pin 8 is. .01mf capacitor connecting signal to the grid. 470K ohm resistor to ground. Pin 9 I have as you stated, however, no matter what I do, there is a signal coming from the cathode. Maybe interference from the two diodes? There are absolutely no other wires connected to the cathode.
::: Pin 7, there are B+++ (170), B++, and B+ (110). voltages. B+ is connected directly to the plate. I will add a 22K ohm resistor and let you know what happens. The schematic shows one, but there is no 22K ohm resistor. I think it shows a 33K ohm resistor. Does this really affect the gain?
:::
:::Thanks,
:::
:::Dave
::::Dave
::::
:::: Must be something obvious here.
::::
:::: Grid is pin #8. This one should have a 470K resistor to ground. A signal needs to be fed in through a cap, .01 mf or similar.
::::
:::: Cathode is pin #9. You have a 1K resistor from this pin to ground. It's bypassed with a 10mf cap. There should be no signal on this pin.
::::
:::: Pin #7 is plate. It should have a resistor to B+, 22K or similar. You can take output from this pin through a cap, .01 mf etc.
::::
:::: Should be no other connections on these pins. Pin #7 may have gone directly to B+ before?
::::
::::Norm
::::
:::::Norm,
::::: Adding the grid resistor decreased the output so that now it's barely audible. It's still there but it's very very quiet. What should I do next?
:::::
:::::Thanks,
:::::
:::::Dave
::::::Norm,
:::::: I had added a 470K because someone removed the volume control (looks like it was done at the factory). Now I've just snipped it out. I'll get another one. There is a resistor feeding a capacitor and the capacitor is connected to the grid.
:::::: Is it normal to have sound coming through the cathode that's louder than through the anode (plate)? I'll try putting back the grid resistor and let you know what happens.
::::::
::::::Thanks,
::::::
::::::Dave
:::::::Dave
:::::::
::::::: The grid may be going too negative? There should already be a grid resistor in your original circuit. If not connect a 470K - 1 meg to ground.
:::::::
::::::: Is the grid capacity coupled? Should be and with a grid resistor added there will be gain.
:::::::
:::::::Norm
:::::::
::::::::Hello Norm,
:::::::: I tried what you said and the signal through the .01 mf capacitor is very weak compared to the input at the grid. There are resistors in the power supply. It's half wave with three resistors and 3 filter capacitors. The plate of the 6BJ8 gets the lowest voltage, which is about 110. The signal going into the amplifier is louder than what's coming out. It's very odd. The tube refuses to turn on. No other wires are attached to it. From the cathode I have the 1 k ohm resistor with the 10 mf capacitor across it. The positive lead of the capacitor is connected to the cathode. The input signal is coming through a disc capacitor to the grid. I can hear signal on both ends of the capacitor. Does there need to be a grid resistor? This is very strange. I have no idea what's going on. It should work but it doesn't.
::::::::
::::::::What do I look at next? The tube tests good. I'll keep trying to get a stronger signal out of it.
::::::::
::::::::Thanks,
::::::::
::::::::Dave
:::::::::Hi Dave
:::::::::
::::::::: Don't have the schematic but here goes... You need a resistor from plate of the 6BJ8 to B+. Use 22K. Take the signal off plate through a .01 mf cap.
:::::::::
::::::::: 6BJ8 has an amplification factor of 20 so should have a cathode resistor. Use 1K here bypassed by a 10 mf electrolytic. Positive toward cathode. Will work with cathode grounded but nay have some distortion.
:::::::::
::::::::: This will increase gain by nearly a factor of 20.
:::::::::
:::::::::Norm
:::::::::
:::::::::
::::::::::Hello All,
:::::::::: I am puzzled by the strange FM output triode connections. The sound comes from the cathode (cathode follower output? no amplification?). The tube doesn't seem to be biased on at all. I'd like to change the circuit so that the triode section of the 6BJ8 has either cathode or fixed bias and the output comes from the anode through a capacitor. What value resistor should I use or can I connect the cathode directly to the chassis (fixed bias). The schematic shows a dropping resistor between the final capacitor and the plate of the triode section, but there is no such resistor in the unit. The schematic is inside the bottom. There is also, no output control. That was eliminated and it looks like it was done at the factory. I would like the triode to act as a pre-amp to boost the output signal higher than what comes through the MPX output jack.
:::::::::: I'm going to try the fixed bias first. All I want to change is the way the triode is operating. I don't wish to make any other changes. I want this to have a line or headphone level output. If anyone knows what the values should be, please let me know. I should know this but never learned it. It's about time I did.
::::::::::
::::::::::Thanks,
::::::::::
::::::::::Dave
::::::::::
:::::::::
:::::::::
::::::::
::::::::
:::::::
:::::::
::::::
::::::
:::::
:::::
::::
::::
:::
:::
::
::
:
: