Your tube has a harder time to oscillate on higher frequencies. Slight changes in the circuit may allow oscillation on broadcast band but not short wave.
Check voltages on your 6SA7. Pins #4, 5 and 6 make up the oscillator circuit. Check that resistors haven't gone up in value. Sometimes dirt or moisture will cause a problem. Clean and let the band switch dry. The positive thing - you know the problem.
Norm
:I received the new metallic tube 6SA7, but does not correct the problem.
::Conclusion: I replaced all of the capacitors and resistors, including the tube 6SA7, Band "B" is working fine, band "C" & "D" do not work, the 6SA7 do not oscillate, no negative voltage present in grid 1, pin 5.
::Somebody can tell me ?Where is the mistery?
::Anybody whit this kind of experience
::Jorge
Hi Jorge
:
: Your tube has a harder time to oscillate on higher frequencies. Slight changes in the circuit may allow oscillation on broadcast band but not short wave.
:
: Check voltages on your 6SA7. Pins #4, 5 and 6 make up the oscillator circuit. Check that resistors haven't gone up in value. Sometimes dirt or moisture will cause a problem. Clean and let the band switch dry. The positive thing - you know the problem.
:
:Norm
:
::I received the new metallic tube 6SA7, but does not correct the problem.
:::Conclusion: I replaced all of the capacitors and resistors, including the tube 6SA7, Band "B" is working fine, band "C" & "D" do not work, the 6SA7 do not oscillate, no negative voltage present in grid 1, pin 5.
:::Somebody can tell me ?Where is the mistery?
:::Anybody whit this kind of experience
:::Jorge
Those voltages show the oscillator isn't operating. When it oscillates grid will go negative. This in turn makes the plate voltage higher.
If you don't find any problem clean and dry the bandswitch. Can you get higher voltage on grid #2 & 4? Sometimes it's supplied through a resistor. A lower value might get the oscillator started? If you have a 6SB7Y try that in place of 6SA7. 6SB7Y is better at higher frequencies.
Norm
:Norm:
:I checked the voltages on 6SA7;
:In band 'B' working are: Pin 4 (grid 2 & 4); 101v. pin 5 (gris 1); -6.5v. Pin 6; 0v:
:In bands 'C' & 'D' not working: Pin 4; 88.6v, Pin 5; -0.08v and pin 6; 0v
:According with the specifications GE H634 in Special Service Information note (3) Average DC voltage developed acroos oscillator gris resistor will be forn Band 'B' between 6 to 8 volts, Band 'C' 5 to 10 volts and for Band 'D' 2 to 5 volts, I checked the voltage between pin 5 and -B.
:I replaced the old resistor for news al 1/2 watt, because the value was alterated, also I replaced all capacitors for news.Also I replaced the wires because the insulation was broken and I checked everything.
:I get this radio for one friend long time ago, never was repaired, now I have the time, and it is a challenge for me, because the next step is working in the case.
:Also is the first time that I saw the 6J5 circuit and I do not undestand how works, because take some retroalimentation from the audio transformer T1.
:Thanks
:Jorge
:
:Hi Jorge
::
:: Your tube has a harder time to oscillate on higher frequencies. Slight changes in the circuit may allow oscillation on broadcast band but not short wave.
::
:: Check voltages on your 6SA7. Pins #4, 5 and 6 make up the oscillator circuit. Check that resistors haven't gone up in value. Sometimes dirt or moisture will cause a problem. Clean and let the band switch dry. The positive thing - you know the problem.
::
::Norm
::
:::I received the new metallic tube 6SA7, but does not correct the problem.
::::Conclusion: I replaced all of the capacitors and resistors, including the tube 6SA7, Band "B" is working fine, band "C" & "D" do not work, the 6SA7 do not oscillate, no negative voltage present in grid 1, pin 5.
::::Somebody can tell me ?Where is the mistery?
::::Anybody whit this kind of experience
::::Jorge
C5 is 2000 pf or .002 mfd. C6 is 5600 pf or .0056 mfd. Did you use these values? C10 should be 47 pf mica.
Did short wave work before the band switch was removed? Was solder flux removed from the switch? It could leave a conductive path.
IF Frequency is 455. As a test use your signal generator as an external oscillator. The radio should work, even on short wave.
Norm
:Norm:
:The voltage to grid #2 & #4, pin4 of the tube 6SA7 is supplied through the resistor R3 (2200 ohms), I checked with different valous until 500ohms, and I incresead the voltaje until 92 volts, but the problem was not corrected, I use 1000 ohms.
:The band switch was removed from the unit, cleared 100%, checked the continuity in all positions and reinstalled, I am sure that the problem is not in the switch.
:I tested with my Signal Tracer (Heathkit IT-12), the bandswitch in B position and the test point in pin 8 of 6SA7 and moving the tuning capacitor I cached one station from Florida in 9.4 MC, but in pin3 (plate) 6SA7 and pin4 4, grid 1 of 6SK7, was no sign, also I check for negative voltage in grid 1 (6SA7),the oscillator 6SA7 is not working.
:I do not have any 6SB7Y.
:Capacitors C5 and C6 are mica capacitors, I used paper capacitor with close value. I replaced all capacitors including electrolitic and also the all resistor, I used brand new components.
:I hope you have more sugestions in base of your experience.
:Thanks
:
: :Jorge
::
:: Those voltages show the oscillator isn't operating. When it oscillates grid will go negative. This in turn makes the plate voltage higher.
::
:: If you don't find any problem clean and dry the bandswitch. Can you get higher voltage on grid #2 & 4? Sometimes it's supplied through a resistor. A lower value might get the oscillator started? If you have a 6SB7Y try that in place of 6SA7. 6SB7Y is better at higher frequencies.
::
::Norm
::
::
:::Norm:
:::I checked the voltages on 6SA7;
:::In band 'B' working are: Pin 4 (grid 2 & 4); 101v. pin 5 (gris 1); -6.5v. Pin 6; 0v:
:::In bands 'C' & 'D' not working: Pin 4; 88.6v, Pin 5; -0.08v and pin 6; 0v
:::According with the specifications GE H634 in Special Service Information note (3) Average DC voltage developed acroos oscillator gris resistor will be forn Band 'B' between 6 to 8 volts, Band 'C' 5 to 10 volts and for Band 'D' 2 to 5 volts, I checked the voltage between pin 5 and -B.
:::I replaced the old resistor for news al 1/2 watt, because the value was alterated, also I replaced all capacitors for news.Also I replaced the wires because the insulation was broken and I checked everything.
:::I get this radio for one friend long time ago, never was repaired, now I have the time, and it is a challenge for me, because the next step is working in the case.
:::Also is the first time that I saw the 6J5 circuit and I do not undestand how works, because take some retroalimentation from the audio transformer T1.
:::Thanks
:::Jorge
:::
:::Hi Jorge
::::
:::: Your tube has a harder time to oscillate on higher frequencies. Slight changes in the circuit may allow oscillation on broadcast band but not short wave.
::::
:::: Check voltages on your 6SA7. Pins #4, 5 and 6 make up the oscillator circuit. Check that resistors haven't gone up in value. Sometimes dirt or moisture will cause a problem. Clean and let the band switch dry. The positive thing - you know the problem.
::::
::::Norm
::::
:::::I received the new metallic tube 6SA7, but does not correct the problem.
::::::Conclusion: I replaced all of the capacitors and resistors, including the tube 6SA7, Band "B" is working fine, band "C" & "D" do not work, the 6SA7 do not oscillate, no negative voltage present in grid 1, pin 5.
::::::Somebody can tell me ?Where is the mistery?
::::::Anybody whit this kind of experience
::::::Jorge
:Jorge
:
: C5 is 2000 pf or .002 mfd. C6 is 5600 pf or .0056 mfd. Did you use these values? C10 should be 47 pf mica.
:
: Did short wave work before the band switch was removed? Was solder flux removed from the switch? It could leave a conductive path.
:
: IF Frequency is 455. As a test use your signal generator as an external oscillator. The radio should work, even on short wave.
:
:Norm
:
::Norm:
::The voltage to grid #2 & #4, pin4 of the tube 6SA7 is supplied through the resistor R3 (2200 ohms), I checked with different valous until 500ohms, and I incresead the voltaje until 92 volts, but the problem was not corrected, I use 1000 ohms.
::The band switch was removed from the unit, cleared 100%, checked the continuity in all positions and reinstalled, I am sure that the problem is not in the switch.
::I tested with my Signal Tracer (Heathkit IT-12), the bandswitch in B position and the test point in pin 8 of 6SA7 and moving the tuning capacitor I cached one station from Florida in 9.4 MC, but in pin3 (plate) 6SA7 and pin4 4, grid 1 of 6SK7, was no sign, also I check for negative voltage in grid 1 (6SA7),the oscillator 6SA7 is not working.
::I do not have any 6SB7Y.
::Capacitors C5 and C6 are mica capacitors, I used paper capacitor with close value. I replaced all capacitors including electrolitic and also the all resistor, I used brand new components.
::I hope you have more sugestions in base of your experience.
::Thanks
::
:: :Jorge
:::
::: Those voltages show the oscillator isn't operating. When it oscillates grid will go negative. This in turn makes the plate voltage higher.
:::
::: If you don't find any problem clean and dry the bandswitch. Can you get higher voltage on grid #2 & 4? Sometimes it's supplied through a resistor. A lower value might get the oscillator started? If you have a 6SB7Y try that in place of 6SA7. 6SB7Y is better at higher frequencies.
:::
:::Norm
:::
:::
::::Norm:
::::I checked the voltages on 6SA7;
::::In band 'B' working are: Pin 4 (grid 2 & 4); 101v. pin 5 (gris 1); -6.5v. Pin 6; 0v:
::::In bands 'C' & 'D' not working: Pin 4; 88.6v, Pin 5; -0.08v and pin 6; 0v
::::According with the specifications GE H634 in Special Service Information note (3) Average DC voltage developed acroos oscillator gris resistor will be forn Band 'B' between 6 to 8 volts, Band 'C' 5 to 10 volts and for Band 'D' 2 to 5 volts, I checked the voltage between pin 5 and -B.
::::I replaced the old resistor for news al 1/2 watt, because the value was alterated, also I replaced all capacitors for news.Also I replaced the wires because the insulation was broken and I checked everything.
::::I get this radio for one friend long time ago, never was repaired, now I have the time, and it is a challenge for me, because the next step is working in the case.
::::Also is the first time that I saw the 6J5 circuit and I do not undestand how works, because take some retroalimentation from the audio transformer T1.
::::Thanks
::::Jorge
::::
::::Hi Jorge
:::::
::::: Your tube has a harder time to oscillate on higher frequencies. Slight changes in the circuit may allow oscillation on broadcast band but not short wave.
:::::
::::: Check voltages on your 6SA7. Pins #4, 5 and 6 make up the oscillator circuit. Check that resistors haven't gone up in value. Sometimes dirt or moisture will cause a problem. Clean and let the band switch dry. The positive thing - you know the problem.
:::::
:::::Norm
:::::
::::::I received the new metallic tube 6SA7, but does not correct the problem.
:::::::Conclusion: I replaced all of the capacitors and resistors, including the tube 6SA7, Band "B" is working fine, band "C" & "D" do not work, the 6SA7 do not oscillate, no negative voltage present in grid 1, pin 5.
:::::::Somebody can tell me ?Where is the mistery?
:::::::Anybody whit this kind of experience
:::::::Jorge
You have checked just about everything, voltage, resistance and changed capacitors.
Have resistors R19 & R20 gone up in value? They are used for short wave.
Even though C10 is used for all bands it will act differently on broadcast & short wave. Higher frequency more signal will pass through a cap of a given value.
Ceramic disk caps aren't the best to use but won't stop the oscillator.
Do both short wave coils have continuity between the three leads?
Alignment of IF Transformers don't have an effect on your oscillator. It has to be working first to get a signal.
Norm
:Hi Norm.
:C5: I used 2 disc capacitor of 0.001 in parallel, total 0.002 or 2000pf.
:C6: I used 3 capacitors, (disc) .005, (mica)500 & 68 total .00568 0r 2,568.
:C10: I used 2 mica capacitor in serie, 250 & 68 total 53.5 pf, this capacitor is common for all frecuencies.
:The short wave was not working before I removed the band switch, this one was cleaned using Radio Shack tuner cleaner and one small brush.
:I followed the alignment procedure for the I.F.and R.F Alignement for band 'B' The radio does not received the frecuencies for alignment the bands 'C' & 'D'
:I used the Specifications fron General Electric Models H634, H638 and H640, by John F. Rider available in nostalgiaair.org
:Whay do you thing?
:Thanks
:Jorge
:
:
:
::Jorge
::
:: C5 is 2000 pf or .002 mfd. C6 is 5600 pf or .0056 mfd. Did you use these values? C10 should be 47 pf mica.
::
:: Did short wave work before the band switch was removed? Was solder flux removed from the switch? It could leave a conductive path.
::
:: IF Frequency is 455. As a test use your signal generator as an external oscillator. The radio should work, even on short wave.
::
::Norm
::
:::Norm:
:::The voltage to grid #2 & #4, pin4 of the tube 6SA7 is supplied through the resistor R3 (2200 ohms), I checked with different valous until 500ohms, and I incresead the voltaje until 92 volts, but the problem was not corrected, I use 1000 ohms.
:::The band switch was removed from the unit, cleared 100%, checked the continuity in all positions and reinstalled, I am sure that the problem is not in the switch.
:::I tested with my Signal Tracer (Heathkit IT-12), the bandswitch in B position and the test point in pin 8 of 6SA7 and moving the tuning capacitor I cached one station from Florida in 9.4 MC, but in pin3 (plate) 6SA7 and pin4 4, grid 1 of 6SK7, was no sign, also I check for negative voltage in grid 1 (6SA7),the oscillator 6SA7 is not working.
:::I do not have any 6SB7Y.
:::Capacitors C5 and C6 are mica capacitors, I used paper capacitor with close value. I replaced all capacitors including electrolitic and also the all resistor, I used brand new components.
:::I hope you have more sugestions in base of your experience.
:::Thanks
:::
::: :Jorge
::::
:::: Those voltages show the oscillator isn't operating. When it oscillates grid will go negative. This in turn makes the plate voltage higher.
::::
:::: If you don't find any problem clean and dry the bandswitch. Can you get higher voltage on grid #2 & 4? Sometimes it's supplied through a resistor. A lower value might get the oscillator started? If you have a 6SB7Y try that in place of 6SA7. 6SB7Y is better at higher frequencies.
::::
::::Norm
::::
::::
:::::Norm:
:::::I checked the voltages on 6SA7;
:::::In band 'B' working are: Pin 4 (grid 2 & 4); 101v. pin 5 (gris 1); -6.5v. Pin 6; 0v:
:::::In bands 'C' & 'D' not working: Pin 4; 88.6v, Pin 5; -0.08v and pin 6; 0v
:::::According with the specifications GE H634 in Special Service Information note (3) Average DC voltage developed acroos oscillator gris resistor will be forn Band 'B' between 6 to 8 volts, Band 'C' 5 to 10 volts and for Band 'D' 2 to 5 volts, I checked the voltage between pin 5 and -B.
:::::I replaced the old resistor for news al 1/2 watt, because the value was alterated, also I replaced all capacitors for news.Also I replaced the wires because the insulation was broken and I checked everything.
:::::I get this radio for one friend long time ago, never was repaired, now I have the time, and it is a challenge for me, because the next step is working in the case.
:::::Also is the first time that I saw the 6J5 circuit and I do not undestand how works, because take some retroalimentation from the audio transformer T1.
:::::Thanks
:::::Jorge
:::::
:::::Hi Jorge
::::::
:::::: Your tube has a harder time to oscillate on higher frequencies. Slight changes in the circuit may allow oscillation on broadcast band but not short wave.
::::::
:::::: Check voltages on your 6SA7. Pins #4, 5 and 6 make up the oscillator circuit. Check that resistors haven't gone up in value. Sometimes dirt or moisture will cause a problem. Clean and let the band switch dry. The positive thing - you know the problem.
::::::
::::::Norm
::::::
:::::::I received the new metallic tube 6SA7, but does not correct the problem.
::::::::Conclusion: I replaced all of the capacitors and resistors, including the tube 6SA7, Band "B" is working fine, band "C" & "D" do not work, the 6SA7 do not oscillate, no negative voltage present in grid 1, pin 5.
::::::::Somebody can tell me ?Where is the mistery?
::::::::Anybody whit this kind of experience
::::::::Jorge
:Hi Jorge
:
:You have checked just about everything, voltage, resistance and changed capacitors.
:
:Have resistors R19 & R20 gone up in value? They are used for short wave.
:
:Even though C10 is used for all bands it will act differently on broadcast & short wave. Higher frequency more signal will pass through a cap of a given value.
:
:Ceramic disk caps aren't the best to use but won't stop the oscillator.
:
:Do both short wave coils have continuity between the three leads?
:
:Alignment of IF Transformers don't have an effect on your oscillator. It has to be working first to get a signal.
:
:Norm
:
:
:
::Hi Norm.
::C5: I used 2 disc capacitor of 0.001 in parallel, total 0.002 or 2000pf.
::C6: I used 3 capacitors, (disc) .005, (mica)500 & 68 total .00568 0r 2,568.
::C10: I used 2 mica capacitor in serie, 250 & 68 total 53.5 pf, this capacitor is common for all frecuencies.
::The short wave was not working before I removed the band switch, this one was cleaned using Radio Shack tuner cleaner and one small brush.
::I followed the alignment procedure for the I.F.and R.F Alignement for band 'B' The radio does not received the frecuencies for alignment the bands 'C' & 'D'
::I used the Specifications fron General Electric Models H634, H638 and H640, by John F. Rider available in nostalgiaair.org
::Whay do you thing?
::Thanks
::Jorge
::
::
::
:::Jorge
:::
::: C5 is 2000 pf or .002 mfd. C6 is 5600 pf or .0056 mfd. Did you use these values? C10 should be 47 pf mica.
:::
::: Did short wave work before the band switch was removed? Was solder flux removed from the switch? It could leave a conductive path.
:::
::: IF Frequency is 455. As a test use your signal generator as an external oscillator. The radio should work, even on short wave.
:::
:::Norm
:::
::::Norm:
::::The voltage to grid #2 & #4, pin4 of the tube 6SA7 is supplied through the resistor R3 (2200 ohms), I checked with different valous until 500ohms, and I incresead the voltaje until 92 volts, but the problem was not corrected, I use 1000 ohms.
::::The band switch was removed from the unit, cleared 100%, checked the continuity in all positions and reinstalled, I am sure that the problem is not in the switch.
::::I tested with my Signal Tracer (Heathkit IT-12), the bandswitch in B position and the test point in pin 8 of 6SA7 and moving the tuning capacitor I cached one station from Florida in 9.4 MC, but in pin3 (plate) 6SA7 and pin4 4, grid 1 of 6SK7, was no sign, also I check for negative voltage in grid 1 (6SA7),the oscillator 6SA7 is not working.
::::I do not have any 6SB7Y.
::::Capacitors C5 and C6 are mica capacitors, I used paper capacitor with close value. I replaced all capacitors including electrolitic and also the all resistor, I used brand new components.
::::I hope you have more sugestions in base of your experience.
::::Thanks
::::
:::: :Jorge
:::::
::::: Those voltages show the oscillator isn't operating. When it oscillates grid will go negative. This in turn makes the plate voltage higher.
:::::
::::: If you don't find any problem clean and dry the bandswitch. Can you get higher voltage on grid #2 & 4? Sometimes it's supplied through a resistor. A lower value might get the oscillator started? If you have a 6SB7Y try that in place of 6SA7. 6SB7Y is better at higher frequencies.
:::::
:::::Norm
:::::
:::::
::::::Norm:
::::::I checked the voltages on 6SA7;
::::::In band 'B' working are: Pin 4 (grid 2 & 4); 101v. pin 5 (gris 1); -6.5v. Pin 6; 0v:
::::::In bands 'C' & 'D' not working: Pin 4; 88.6v, Pin 5; -0.08v and pin 6; 0v
::::::According with the specifications GE H634 in Special Service Information note (3) Average DC voltage developed acroos oscillator gris resistor will be forn Band 'B' between 6 to 8 volts, Band 'C' 5 to 10 volts and for Band 'D' 2 to 5 volts, I checked the voltage between pin 5 and -B.
::::::I replaced the old resistor for news al 1/2 watt, because the value was alterated, also I replaced all capacitors for news.Also I replaced the wires because the insulation was broken and I checked everything.
::::::I get this radio for one friend long time ago, never was repaired, now I have the time, and it is a challenge for me, because the next step is working in the case.
::::::Also is the first time that I saw the 6J5 circuit and I do not undestand how works, because take some retroalimentation from the audio transformer T1.
::::::Thanks
::::::Jorge
::::::
::::::Hi Jorge
:::::::
::::::: Your tube has a harder time to oscillate on higher frequencies. Slight changes in the circuit may allow oscillation on broadcast band but not short wave.
:::::::
::::::: Check voltages on your 6SA7. Pins #4, 5 and 6 make up the oscillator circuit. Check that resistors haven't gone up in value. Sometimes dirt or moisture will cause a problem. Clean and let the band switch dry. The positive thing - you know the problem.
:::::::
:::::::Norm
:::::::
::::::::I received the new metallic tube 6SA7, but does not correct the problem.
:::::::::Conclusion: I replaced all of the capacitors and resistors, including the tube 6SA7, Band "B" is working fine, band "C" & "D" do not work, the 6SA7 do not oscillate, no negative voltage present in grid 1, pin 5.
:::::::::Somebody can tell me ?Where is the mistery?
:::::::::Anybody whit this kind of experience
:::::::::Jorge
:Hi Norm:
:Resistors R19 and R20 are brand new resistors 150 and 68 ohms
:I replaced the capacitor c10 for 47 pf.
:All coils are OK, tested out of the circuit.
:When I connected the antenna to the terminal at the end of capacitor C19, I do not hear any clic or noise.
:Jorge
:
::Hi Jorge
::
::You have checked just about everything, voltage, resistance and changed capacitors.
::
::Have resistors R19 & R20 gone up in value? They are used for short wave.
::
::Even though C10 is used for all bands it will act differently on broadcast & short wave. Higher frequency more signal will pass through a cap of a given value.
::
::Ceramic disk caps aren't the best to use but won't stop the oscillator.
::
::Do both short wave coils have continuity between the three leads?
::
::Alignment of IF Transformers don't have an effect on your oscillator. It has to be working first to get a signal.
::
::Norm
::
::
::
:::Hi Norm.
:::C5: I used 2 disc capacitor of 0.001 in parallel, total 0.002 or 2000pf.
:::C6: I used 3 capacitors, (disc) .005, (mica)500 & 68 total .00568 0r 2,568.
:::C10: I used 2 mica capacitor in serie, 250 & 68 total 53.5 pf, this capacitor is common for all frecuencies.
:::The short wave was not working before I removed the band switch, this one was cleaned using Radio Shack tuner cleaner and one small brush.
:::I followed the alignment procedure for the I.F.and R.F Alignement for band 'B' The radio does not received the frecuencies for alignment the bands 'C' & 'D'
:::I used the Specifications fron General Electric Models H634, H638 and H640, by John F. Rider available in nostalgiaair.org
:::Whay do you thing?
:::Thanks
:::Jorge
:::
:::
:::
::::Jorge
::::
:::: C5 is 2000 pf or .002 mfd. C6 is 5600 pf or .0056 mfd. Did you use these values? C10 should be 47 pf mica.
::::
:::: Did short wave work before the band switch was removed? Was solder flux removed from the switch? It could leave a conductive path.
::::
:::: IF Frequency is 455. As a test use your signal generator as an external oscillator. The radio should work, even on short wave.
::::
::::Norm
::::
:::::Norm:
:::::The voltage to grid #2 & #4, pin4 of the tube 6SA7 is supplied through the resistor R3 (2200 ohms), I checked with different valous until 500ohms, and I incresead the voltaje until 92 volts, but the problem was not corrected, I use 1000 ohms.
:::::The band switch was removed from the unit, cleared 100%, checked the continuity in all positions and reinstalled, I am sure that the problem is not in the switch.
:::::I tested with my Signal Tracer (Heathkit IT-12), the bandswitch in B position and the test point in pin 8 of 6SA7 and moving the tuning capacitor I cached one station from Florida in 9.4 MC, but in pin3 (plate) 6SA7 and pin4 4, grid 1 of 6SK7, was no sign, also I check for negative voltage in grid 1 (6SA7),the oscillator 6SA7 is not working.
:::::I do not have any 6SB7Y.
:::::Capacitors C5 and C6 are mica capacitors, I used paper capacitor with close value. I replaced all capacitors including electrolitic and also the all resistor, I used brand new components.
:::::I hope you have more sugestions in base of your experience.
:::::Thanks
:::::
::::: :Jorge
::::::
:::::: Those voltages show the oscillator isn't operating. When it oscillates grid will go negative. This in turn makes the plate voltage higher.
::::::
:::::: If you don't find any problem clean and dry the bandswitch. Can you get higher voltage on grid #2 & 4? Sometimes it's supplied through a resistor. A lower value might get the oscillator started? If you have a 6SB7Y try that in place of 6SA7. 6SB7Y is better at higher frequencies.
::::::
::::::Norm
::::::
::::::
:::::::Norm:
:::::::I checked the voltages on 6SA7;
:::::::In band 'B' working are: Pin 4 (grid 2 & 4); 101v. pin 5 (gris 1); -6.5v. Pin 6; 0v:
:::::::In bands 'C' & 'D' not working: Pin 4; 88.6v, Pin 5; -0.08v and pin 6; 0v
:::::::According with the specifications GE H634 in Special Service Information note (3) Average DC voltage developed acroos oscillator gris resistor will be forn Band 'B' between 6 to 8 volts, Band 'C' 5 to 10 volts and for Band 'D' 2 to 5 volts, I checked the voltage between pin 5 and -B.
:::::::I replaced the old resistor for news al 1/2 watt, because the value was alterated, also I replaced all capacitors for news.Also I replaced the wires because the insulation was broken and I checked everything.
:::::::I get this radio for one friend long time ago, never was repaired, now I have the time, and it is a challenge for me, because the next step is working in the case.
:::::::Also is the first time that I saw the 6J5 circuit and I do not undestand how works, because take some retroalimentation from the audio transformer T1.
:::::::Thanks
:::::::Jorge
:::::::
:::::::Hi Jorge
::::::::
:::::::: Your tube has a harder time to oscillate on higher frequencies. Slight changes in the circuit may allow oscillation on broadcast band but not short wave.
::::::::
:::::::: Check voltages on your 6SA7. Pins #4, 5 and 6 make up the oscillator circuit. Check that resistors haven't gone up in value. Sometimes dirt or moisture will cause a problem. Clean and let the band switch dry. The positive thing - you know the problem.
::::::::
::::::::Norm
::::::::
:::::::::I received the new metallic tube 6SA7, but does not correct the problem.
::::::::::Conclusion: I replaced all of the capacitors and resistors, including the tube 6SA7, Band "B" is working fine, band "C" & "D" do not work, the 6SA7 do not oscillate, no negative voltage present in grid 1, pin 5.
::::::::::Somebody can tell me ?Where is the mistery?
::::::::::Anybody whit this kind of experience
::::::::::Jorge
:Hi Norm:
:Resistors R19 and R20 are brand new resistors 150 and 68 ohms
:I replaced the capacitor c10 for 47 pf.
:All coils are OK, tested out of the circuit.
:When I connected the antenna to the terminal at the end of capacitor C19, I do not hear any clic or noise.
:Jorge
:
::Hi Jorge
::
::You have checked just about everything, voltage, resistance and changed capacitors.
::
::Have resistors R19 & R20 gone up in value? They are used for short wave.
::
::Even though C10 is used for all bands it will act differently on broadcast & short wave. Higher frequency more signal will pass through a cap of a given value.
::
::Ceramic disk caps aren't the best to use but won't stop the oscillator.
::
::Do both short wave coils have continuity between the three leads?
::
::Alignment of IF Transformers don't have an effect on your oscillator. It has to be working first to get a signal.
::
::Norm
::
::
::
:::Hi Norm.
:::C5: I used 2 disc capacitor of 0.001 in parallel, total 0.002 or 2000pf.
:::C6: I used 3 capacitors, (disc) .005, (mica)500 & 68 total .00568 0r 2,568.
:::C10: I used 2 mica capacitor in serie, 250 & 68 total 53.5 pf, this capacitor is common for all frecuencies.
:::The short wave was not working before I removed the band switch, this one was cleaned using Radio Shack tuner cleaner and one small brush.
:::I followed the alignment procedure for the I.F.and R.F Alignement for band 'B' The radio does not received the frecuencies for alignment the bands 'C' & 'D'
:::I used the Specifications fron General Electric Models H634, H638 and H640, by John F. Rider available in nostalgiaair.org
:::Whay do you thing?
:::Thanks
:::Jorge
:::
:::
:::
::::Jorge
::::
:::: C5 is 2000 pf or .002 mfd. C6 is 5600 pf or .0056 mfd. Did you use these values? C10 should be 47 pf mica.
::::
:::: Did short wave work before the band switch was removed? Was solder flux removed from the switch? It could leave a conductive path.
::::
:::: IF Frequency is 455. As a test use your signal generator as an external oscillator. The radio should work, even on short wave.
::::
::::Norm
::::
:::::Norm:
:::::The voltage to grid #2 & #4, pin4 of the tube 6SA7 is supplied through the resistor R3 (2200 ohms), I checked with different valous until 500ohms, and I incresead the voltaje until 92 volts, but the problem was not corrected, I use 1000 ohms.
:::::The band switch was removed from the unit, cleared 100%, checked the continuity in all positions and reinstalled, I am sure that the problem is not in the switch.
:::::I tested with my Signal Tracer (Heathkit IT-12), the bandswitch in B position and the test point in pin 8 of 6SA7 and moving the tuning capacitor I cached one station from Florida in 9.4 MC, but in pin3 (plate) 6SA7 and pin4 4, grid 1 of 6SK7, was no sign, also I check for negative voltage in grid 1 (6SA7),the oscillator 6SA7 is not working.
:::::I do not have any 6SB7Y.
:::::Capacitors C5 and C6 are mica capacitors, I used paper capacitor with close value. I replaced all capacitors including electrolitic and also the all resistor, I used brand new components.
:::::I hope you have more sugestions in base of your experience.
:::::Thanks
:::::
::::: :Jorge
::::::
:::::: Those voltages show the oscillator isn't operating. When it oscillates grid will go negative. This in turn makes the plate voltage higher.
::::::
:::::: If you don't find any problem clean and dry the bandswitch. Can you get higher voltage on grid #2 & 4? Sometimes it's supplied through a resistor. A lower value might get the oscillator started? If you have a 6SB7Y try that in place of 6SA7. 6SB7Y is better at higher frequencies.
::::::
::::::Norm
::::::
::::::
:::::::Norm:
:::::::I checked the voltages on 6SA7;
:::::::In band 'B' working are: Pin 4 (grid 2 & 4); 101v. pin 5 (gris 1); -6.5v. Pin 6; 0v:
:::::::In bands 'C' & 'D' not working: Pin 4; 88.6v, Pin 5; -0.08v and pin 6; 0v
:::::::According with the specifications GE H634 in Special Service Information note (3) Average DC voltage developed acroos oscillator gris resistor will be forn Band 'B' between 6 to 8 volts, Band 'C' 5 to 10 volts and for Band 'D' 2 to 5 volts, I checked the voltage between pin 5 and -B.
:::::::I replaced the old resistor for news al 1/2 watt, because the value was alterated, also I replaced all capacitors for news.Also I replaced the wires because the insulation was broken and I checked everything.
:::::::I get this radio for one friend long time ago, never was repaired, now I have the time, and it is a challenge for me, because the next step is working in the case.
:::::::Also is the first time that I saw the 6J5 circuit and I do not undestand how works, because take some retroalimentation from the audio transformer T1.
:::::::Thanks
:::::::Jorge
:::::::
:::::::Hi Jorge
::::::::
:::::::: Your tube has a harder time to oscillate on higher frequencies. Slight changes in the circuit may allow oscillation on broadcast band but not short wave.
::::::::
:::::::: Check voltages on your 6SA7. Pins #4, 5 and 6 make up the oscillator circuit. Check that resistors haven't gone up in value. Sometimes dirt or moisture will cause a problem. Clean and let the band switch dry. The positive thing - you know the problem.
::::::::
::::::::Norm
::::::::
:::::::::I received the new metallic tube 6SA7, but does not correct the problem.
::::::::::Conclusion: I replaced all of the capacitors and resistors, including the tube 6SA7, Band "B" is working fine, band "C" & "D" do not work, the 6SA7 do not oscillate, no negative voltage present in grid 1, pin 5.
::::::::::Somebody can tell me ?Where is the mistery?
::::::::::Anybody whit this kind of experience
::::::::::Jorge
6SB7Y is directly interchangeable with 6SA7. It does a better job on short wave and has a low loss base. 6SB7Y was originally made for FM which is much higher in frequency.
Changing over may fix your problem if it's due to slight leakages but not a miswire or bad component.
Send an email with your address..
Norm
:Somebody have the experience of change 6SA7 by 6SB7Y?
:How works the short wave?
:Jorge
:
:
:
:
::Hi Norm:
::Resistors R19 and R20 are brand new resistors 150 and 68 ohms
::I replaced the capacitor c10 for 47 pf.
::All coils are OK, tested out of the circuit.
::When I connected the antenna to the terminal at the end of capacitor C19, I do not hear any clic or noise.
::Jorge
::
:::Hi Jorge
:::
:::You have checked just about everything, voltage, resistance and changed capacitors.
:::
:::Have resistors R19 & R20 gone up in value? They are used for short wave.
:::
:::Even though C10 is used for all bands it will act differently on broadcast & short wave. Higher frequency more signal will pass through a cap of a given value.
:::
:::Ceramic disk caps aren't the best to use but won't stop the oscillator.
:::
:::Do both short wave coils have continuity between the three leads?
:::
:::Alignment of IF Transformers don't have an effect on your oscillator. It has to be working first to get a signal.
:::
:::Norm
:::
:::
:::
::::Hi Norm.
::::C5: I used 2 disc capacitor of 0.001 in parallel, total 0.002 or 2000pf.
::::C6: I used 3 capacitors, (disc) .005, (mica)500 & 68 total .00568 0r 2,568.
::::C10: I used 2 mica capacitor in serie, 250 & 68 total 53.5 pf, this capacitor is common for all frecuencies.
::::The short wave was not working before I removed the band switch, this one was cleaned using Radio Shack tuner cleaner and one small brush.
::::I followed the alignment procedure for the I.F.and R.F Alignement for band 'B' The radio does not received the frecuencies for alignment the bands 'C' & 'D'
::::I used the Specifications fron General Electric Models H634, H638 and H640, by John F. Rider available in nostalgiaair.org
::::Whay do you thing?
::::Thanks
::::Jorge
::::
::::
::::
:::::Jorge
:::::
::::: C5 is 2000 pf or .002 mfd. C6 is 5600 pf or .0056 mfd. Did you use these values? C10 should be 47 pf mica.
:::::
::::: Did short wave work before the band switch was removed? Was solder flux removed from the switch? It could leave a conductive path.
:::::
::::: IF Frequency is 455. As a test use your signal generator as an external oscillator. The radio should work, even on short wave.
:::::
:::::Norm
:::::
::::::Norm:
::::::The voltage to grid #2 & #4, pin4 of the tube 6SA7 is supplied through the resistor R3 (2200 ohms), I checked with different valous until 500ohms, and I incresead the voltaje until 92 volts, but the problem was not corrected, I use 1000 ohms.
::::::The band switch was removed from the unit, cleared 100%, checked the continuity in all positions and reinstalled, I am sure that the problem is not in the switch.
::::::I tested with my Signal Tracer (Heathkit IT-12), the bandswitch in B position and the test point in pin 8 of 6SA7 and moving the tuning capacitor I cached one station from Florida in 9.4 MC, but in pin3 (plate) 6SA7 and pin4 4, grid 1 of 6SK7, was no sign, also I check for negative voltage in grid 1 (6SA7),the oscillator 6SA7 is not working.
::::::I do not have any 6SB7Y.
::::::Capacitors C5 and C6 are mica capacitors, I used paper capacitor with close value. I replaced all capacitors including electrolitic and also the all resistor, I used brand new components.
::::::I hope you have more sugestions in base of your experience.
::::::Thanks
::::::
:::::: :Jorge
:::::::
::::::: Those voltages show the oscillator isn't operating. When it oscillates grid will go negative. This in turn makes the plate voltage higher.
:::::::
::::::: If you don't find any problem clean and dry the bandswitch. Can you get higher voltage on grid #2 & 4? Sometimes it's supplied through a resistor. A lower value might get the oscillator started? If you have a 6SB7Y try that in place of 6SA7. 6SB7Y is better at higher frequencies.
:::::::
:::::::Norm
:::::::
:::::::
::::::::Norm:
::::::::I checked the voltages on 6SA7;
::::::::In band 'B' working are: Pin 4 (grid 2 & 4); 101v. pin 5 (gris 1); -6.5v. Pin 6; 0v:
::::::::In bands 'C' & 'D' not working: Pin 4; 88.6v, Pin 5; -0.08v and pin 6; 0v
::::::::According with the specifications GE H634 in Special Service Information note (3) Average DC voltage developed acroos oscillator gris resistor will be forn Band 'B' between 6 to 8 volts, Band 'C' 5 to 10 volts and for Band 'D' 2 to 5 volts, I checked the voltage between pin 5 and -B.
::::::::I replaced the old resistor for news al 1/2 watt, because the value was alterated, also I replaced all capacitors for news.Also I replaced the wires because the insulation was broken and I checked everything.
::::::::I get this radio for one friend long time ago, never was repaired, now I have the time, and it is a challenge for me, because the next step is working in the case.
::::::::Also is the first time that I saw the 6J5 circuit and I do not undestand how works, because take some retroalimentation from the audio transformer T1.
::::::::Thanks
::::::::Jorge
::::::::
::::::::Hi Jorge
:::::::::
::::::::: Your tube has a harder time to oscillate on higher frequencies. Slight changes in the circuit may allow oscillation on broadcast band but not short wave.
:::::::::
::::::::: Check voltages on your 6SA7. Pins #4, 5 and 6 make up the oscillator circuit. Check that resistors haven't gone up in value. Sometimes dirt or moisture will cause a problem. Clean and let the band switch dry. The positive thing - you know the problem.
:::::::::
:::::::::Norm
:::::::::
::::::::::I received the new metallic tube 6SA7, but does not correct the problem.
:::::::::::Conclusion: I replaced all of the capacitors and resistors, including the tube 6SA7, Band "B" is working fine, band "C" & "D" do not work, the 6SA7 do not oscillate, no negative voltage present in grid 1, pin 5.
:::::::::::Somebody can tell me ?Where is the mistery?
:::::::::::Anybody whit this kind of experience
:::::::::::Jorge