I recently recapped a zenith 5s127 as well as changed some out-of-spec resistors.
I am having trouble aligning and have weak reception/volume. Checking the pin voltages several are off significantly.
1st det/osc tube: pin 5 is +4.6, should be -1vdc; pin 6 is 204vdc,
should be 166vdc.
2nd det/AVC tube: pin 3 is 127vdc, should be 75vdc; pins 4&5 are
1.4vdc, should be 0.1.
Also top cap (pin 9) of 1st det/osc and IF tubes measure .4mvAC.
Should be 0. Top of 2nd det/AVC measures 1.1mvAC.
I get sound good sound when I touch the top osc cap with the volt meter (pick up station). Some weak sound if I touch the IF tube cap. Noise/hum if I touch the AVC tube cap. Volume fads significantly and voltage drops if I touch the chassis.
Any ideas on where to start? Could I have made a mistake on a resistor or is something shorted?
schematic here: http://www.nostalgiaair.org/Resources/888/M0024888.htm
Important to have pin #5 on your 6A8 negative several volts in relation to pin #8. This shows the oscillator is operating.
Check the oscillator coil (10) for continuity and other components around this tube. Try another 6A8 if you have one.
Touching top of the 6Q7 you should hear a loud hum. If you hear this noise the audio section is ok. Don't worry about plate voltage (pin 3) reading on this tube. Voltage is supplied through a large value resistor (R8) and meters load it down differently. Older meaters will give lower readings.
AVC voltage will vary by signal strength going negative when a strong station is received.
Norm
:I'm a novice at this but learning the hardway.
:
:I recently recapped a zenith 5s127 as well as changed some out-of-spec resistors.
:
:
:I am having trouble aligning and have weak reception/volume. Checking the pin voltages several are off significantly.
:
:
:1st det/osc tube: pin 5 is +4.6, should be -1vdc; pin 6 is 204vdc,
:should be 166vdc.
:2nd det/AVC tube: pin 3 is 127vdc, should be 75vdc; pins 4&5 are
:1.4vdc, should be 0.1.
:
:
:Also top cap (pin 9) of 1st det/osc and IF tubes measure .4mvAC.
:Should be 0. Top of 2nd det/AVC measures 1.1mvAC.
:
:
:I get sound good sound when I touch the top osc cap with the volt meter (pick up station). Some weak sound if I touch the IF tube cap. Noise/hum if I touch the AVC tube cap. Volume fads significantly and voltage drops if I touch the chassis.
:
:
:Any ideas on where to start? Could I have made a mistake on a resistor or is something shorted?
:
:
:schematic here: http://www.nostalgiaair.org/Resources/888/M0024888.htm
:
:
Important to have pin #5 on your 6A8 negative several volts in relation to pin #8. This shows the oscillator is operating.
Check the oscillator coil (10) for continuity and other components around this tube. Try another 6A8 if you have one.
Touching top of the 6Q7 you should hear a loud hum. If you hear this noise the audio section is ok. Don't worry about plate voltage (pin 3) reading on this tube. Voltage is supplied through a large value resistor (R8) and meters load it down differently. Older meaters will give lower readings.
AVC voltage will vary by signal strength going negative when a strong station is received.
Norm
:I'm a novice at this but learning the hardway.
:
:I recently recapped a zenith 5s127 as well as changed some out-of-spec resistors.
:
:
:I am having trouble aligning and have weak reception/volume. Checking the pin voltages several are off significantly.
:
:
:1st det/osc tube: pin 5 is +4.6, should be -1vdc; pin 6 is 204vdc,
:should be 166vdc.
:2nd det/AVC tube: pin 3 is 127vdc, should be 75vdc; pins 4&5 are
:1.4vdc, should be 0.1.
:
:
:Also top cap (pin 9) of 1st det/osc and IF tubes measure .4mvAC.
:Should be 0. Top of 2nd det/AVC measures 1.1mvAC.
:
:
:I get sound good sound when I touch the top osc cap with the volt meter (pick up station). Some weak sound if I touch the IF tube cap. Noise/hum if I touch the AVC tube cap. Volume fads significantly and voltage drops if I touch the chassis.
:
:
:Any ideas on where to start? Could I have made a mistake on a resistor or is something shorted?
:
:
:schematic here: http://www.nostalgiaair.org/Resources/888/M0024888.htm
:
:
I checked the continuity on the osc coil and it looks good. I double checked the 6a8 tube on my knight tester and it measures 70 and 75 on the two tests listed. I do get a hum on the 6q7 tube.
Do you think it's the 6a8 tube or something else? I don't have a spare to test.
Tim.
:Tim
:
: Important to have pin #5 on your 6A8 negative several volts in relation to pin #8. This shows the oscillator is operating.
:
: Check the oscillator coil (10) for continuity and other components around this tube. Try another 6A8 if you have one.
:
: Touching top of the 6Q7 you should hear a loud hum. If you hear this noise the audio section is ok. Don't worry about plate voltage (pin 3) reading on this tube. Voltage is supplied through a large value resistor (R8) and meters load it down differently. Older meaters will give lower readings.
:
: AVC voltage will vary by signal strength going negative when a strong station is received.
:
:Norm
:
::I'm a novice at this but learning the hardway.
::
::I recently recapped a zenith 5s127 as well as changed some out-of-spec resistors.
::
::
::I am having trouble aligning and have weak reception/volume. Checking the pin voltages several are off significantly.
::
::
::1st det/osc tube: pin 5 is +4.6, should be -1vdc; pin 6 is 204vdc,
::should be 166vdc.
::2nd det/AVC tube: pin 3 is 127vdc, should be 75vdc; pins 4&5 are
::1.4vdc, should be 0.1.
::
::
::Also top cap (pin 9) of 1st det/osc and IF tubes measure .4mvAC.
::Should be 0. Top of 2nd det/AVC measures 1.1mvAC.
::
::
::I get sound good sound when I touch the top osc cap with the volt meter (pick up station). Some weak sound if I touch the IF tube cap. Noise/hum if I touch the AVC tube cap. Volume fads significantly and voltage drops if I touch the chassis.
::
::
::Any ideas on where to start? Could I have made a mistake on a resistor or is something shorted?
::
::
::schematic here: http://www.nostalgiaair.org/Resources/888/M0024888.htm
::
::
Something is causing you oscillator not to operate giving negative grid voltage. Even though a 6A8 tests ok on a tester some will not oscillate in a circuit.
I would check resistors and voltages around this tube first. Pin #5, #6 and #8 make up the oscillator circuit on a 6A8.
Norm
:
Norm,
:
:I checked the continuity on the osc coil and it looks good. I double checked the 6a8 tube on my knight tester and it measures 70 and 75 on the two tests listed. I do get a hum on the 6q7 tube.
:
:Do you think it's the 6a8 tube or something else? I don't have a spare to test.
:
:Tim.
:
::Tim
::
:: Important to have pin #5 on your 6A8 negative several volts in relation to pin #8. This shows the oscillator is operating.
::
:: Check the oscillator coil (10) for continuity and other components around this tube. Try another 6A8 if you have one.
::
:: Touching top of the 6Q7 you should hear a loud hum. If you hear this noise the audio section is ok. Don't worry about plate voltage (pin 3) reading on this tube. Voltage is supplied through a large value resistor (R8) and meters load it down differently. Older meaters will give lower readings.
::
:: AVC voltage will vary by signal strength going negative when a strong station is received.
::
::Norm
::
:::I'm a novice at this but learning the hardway.
:::
:::I recently recapped a zenith 5s127 as well as changed some out-of-spec resistors.
:::
:::
:::I am having trouble aligning and have weak reception/volume. Checking the pin voltages several are off significantly.
:::
:::
:::1st det/osc tube: pin 5 is +4.6, should be -1vdc; pin 6 is 204vdc,
:::should be 166vdc.
:::2nd det/AVC tube: pin 3 is 127vdc, should be 75vdc; pins 4&5 are
:::1.4vdc, should be 0.1.
:::
:::
:::Also top cap (pin 9) of 1st det/osc and IF tubes measure .4mvAC.
:::Should be 0. Top of 2nd det/AVC measures 1.1mvAC.
:::
:::
:::I get sound good sound when I touch the top osc cap with the volt meter (pick up station). Some weak sound if I touch the IF tube cap. Noise/hum if I touch the AVC tube cap. Volume fads significantly and voltage drops if I touch the chassis.
:::
:::
:::Any ideas on where to start? Could I have made a mistake on a resistor or is something shorted?
:::
:::
:::schematic here: http://www.nostalgiaair.org/Resources/888/M0024888.htm
:::
:::
:Tim
:
: Something is causing you oscillator not to operate giving negative grid voltage. Even though a 6A8 tests ok on a tester some will not oscillate in a circuit.
:
: I would check resistors and voltages around this tube first. Pin #5, #6 and #8 make up the oscillator circuit on a 6A8.
:
:Norm
:
::
:
:
:Norm,
::
::I checked the continuity on the osc coil and it looks good. I double checked the 6a8 tube on my knight tester and it measures 70 and 75 on the two tests listed. I do get a hum on the 6q7 tube.
::
::Do you think it's the 6a8 tube or something else? I don't have a spare to test.
::
::Tim.
::
:::Tim
:::
::: Important to have pin #5 on your 6A8 negative several volts in relation to pin #8. This shows the oscillator is operating.
:::
::: Check the oscillator coil (10) for continuity and other components around this tube. Try another 6A8 if you have one.
:::
::: Touching top of the 6Q7 you should hear a loud hum. If you hear this noise the audio section is ok. Don't worry about plate voltage (pin 3) reading on this tube. Voltage is supplied through a large value resistor (R8) and meters load it down differently. Older meaters will give lower readings.
:::
::: AVC voltage will vary by signal strength going negative when a strong station is received.
:::
:::Norm
:::
::::I'm a novice at this but learning the hardway.
::::
::::I recently recapped a zenith 5s127 as well as changed some out-of-spec resistors.
::::
::::
::::I am having trouble aligning and have weak reception/volume. Checking the pin voltages several are off significantly.
::::
::::
::::1st det/osc tube: pin 5 is +4.6, should be -1vdc; pin 6 is 204vdc,
::::should be 166vdc.
::::2nd det/AVC tube: pin 3 is 127vdc, should be 75vdc; pins 4&5 are
::::1.4vdc, should be 0.1.
::::
::::
::::Also top cap (pin 9) of 1st det/osc and IF tubes measure .4mvAC.
::::Should be 0. Top of 2nd det/AVC measures 1.1mvAC.
::::
::::
::::I get sound good sound when I touch the top osc cap with the volt meter (pick up station). Some weak sound if I touch the IF tube cap. Noise/hum if I touch the AVC tube cap. Volume fads significantly and voltage drops if I touch the chassis.
::::
::::
::::Any ideas on where to start? Could I have made a mistake on a resistor or is something shorted?
::::
::::
::::schematic here: http://www.nostalgiaair.org/Resources/888/M0024888.htm
::::
::::
By cap do you mean top of the 6A8? If it picks up stations and tunes correctly it's not the 6A8 tube. If you hear one station across most of the band the oscillator isn't operating.
If the radio operates correctly while touching top of the 6A8 something in the antenna coil circuit is open.
Norm
:I checked all the nearby resistors and did not find anything out of spec or hooked up incorrectly. I will get a new tube and see if that is the issue. It's odd how well it plays when I touch the cap. Based on what I read, that most likely means a weak osc tube. Do you agree?
:
::Tim
::
:: Something is causing you oscillator not to operate giving negative grid voltage. Even though a 6A8 tests ok on a tester some will not oscillate in a circuit.
::
:: I would check resistors and voltages around this tube first. Pin #5, #6 and #8 make up the oscillator circuit on a 6A8.
::
::Norm
::
:::
::
::
::Norm,
:::
:::I checked the continuity on the osc coil and it looks good. I double checked the 6a8 tube on my knight tester and it measures 70 and 75 on the two tests listed. I do get a hum on the 6q7 tube.
:::
:::Do you think it's the 6a8 tube or something else? I don't have a spare to test.
:::
:::Tim.
:::
::::Tim
::::
:::: Important to have pin #5 on your 6A8 negative several volts in relation to pin #8. This shows the oscillator is operating.
::::
:::: Check the oscillator coil (10) for continuity and other components around this tube. Try another 6A8 if you have one.
::::
:::: Touching top of the 6Q7 you should hear a loud hum. If you hear this noise the audio section is ok. Don't worry about plate voltage (pin 3) reading on this tube. Voltage is supplied through a large value resistor (R8) and meters load it down differently. Older meaters will give lower readings.
::::
:::: AVC voltage will vary by signal strength going negative when a strong station is received.
::::
::::Norm
::::
:::::I'm a novice at this but learning the hardway.
:::::
:::::I recently recapped a zenith 5s127 as well as changed some out-of-spec resistors.
:::::
:::::
:::::I am having trouble aligning and have weak reception/volume. Checking the pin voltages several are off significantly.
:::::
:::::
:::::1st det/osc tube: pin 5 is +4.6, should be -1vdc; pin 6 is 204vdc,
:::::should be 166vdc.
:::::2nd det/AVC tube: pin 3 is 127vdc, should be 75vdc; pins 4&5 are
:::::1.4vdc, should be 0.1.
:::::
:::::
:::::Also top cap (pin 9) of 1st det/osc and IF tubes measure .4mvAC.
:::::Should be 0. Top of 2nd det/AVC measures 1.1mvAC.
:::::
:::::
:::::I get sound good sound when I touch the top osc cap with the volt meter (pick up station). Some weak sound if I touch the IF tube cap. Noise/hum if I touch the AVC tube cap. Volume fads significantly and voltage drops if I touch the chassis.
:::::
:::::
:::::Any ideas on where to start? Could I have made a mistake on a resistor or is something shorted?
:::::
:::::
:::::schematic here: http://www.nostalgiaair.org/Resources/888/M0024888.htm
:::::
:::::
I recheck the antenna coil area.
:Tim
:
: By cap do you mean top of the 6A8? If it picks up stations and tunes correctly it's not the 6A8 tube. If you hear one station across most of the band the oscillator isn't operating.
:
: If the radio operates correctly while touching top of the 6A8 something in the antenna coil circuit is open.
:
:Norm
:
:
:
::I checked all the nearby resistors and did not find anything out of spec or hooked up incorrectly. I will get a new tube and see if that is the issue. It's odd how well it plays when I touch the cap. Based on what I read, that most likely means a weak osc tube. Do you agree?
::
:::Tim
:::
::: Something is causing you oscillator not to operate giving negative grid voltage. Even though a 6A8 tests ok on a tester some will not oscillate in a circuit.
:::
::: I would check resistors and voltages around this tube first. Pin #5, #6 and #8 make up the oscillator circuit on a 6A8.
:::
:::Norm
:::
::::
:::
:::
:::Norm,
::::
::::I checked the continuity on the osc coil and it looks good. I double checked the 6a8 tube on my knight tester and it measures 70 and 75 on the two tests listed. I do get a hum on the 6q7 tube.
::::
::::Do you think it's the 6a8 tube or something else? I don't have a spare to test.
::::
::::Tim.
::::
:::::Tim
:::::
::::: Important to have pin #5 on your 6A8 negative several volts in relation to pin #8. This shows the oscillator is operating.
:::::
::::: Check the oscillator coil (10) for continuity and other components around this tube. Try another 6A8 if you have one.
:::::
::::: Touching top of the 6Q7 you should hear a loud hum. If you hear this noise the audio section is ok. Don't worry about plate voltage (pin 3) reading on this tube. Voltage is supplied through a large value resistor (R8) and meters load it down differently. Older meaters will give lower readings.
:::::
::::: AVC voltage will vary by signal strength going negative when a strong station is received.
:::::
:::::Norm
:::::
::::::I'm a novice at this but learning the hardway.
::::::
::::::I recently recapped a zenith 5s127 as well as changed some out-of-spec resistors.
::::::
::::::
::::::I am having trouble aligning and have weak reception/volume. Checking the pin voltages several are off significantly.
::::::
::::::
::::::1st det/osc tube: pin 5 is +4.6, should be -1vdc; pin 6 is 204vdc,
::::::should be 166vdc.
::::::2nd det/AVC tube: pin 3 is 127vdc, should be 75vdc; pins 4&5 are
::::::1.4vdc, should be 0.1.
::::::
::::::
::::::Also top cap (pin 9) of 1st det/osc and IF tubes measure .4mvAC.
::::::Should be 0. Top of 2nd det/AVC measures 1.1mvAC.
::::::
::::::
::::::I get sound good sound when I touch the top osc cap with the volt meter (pick up station). Some weak sound if I touch the IF tube cap. Noise/hum if I touch the AVC tube cap. Volume fads significantly and voltage drops if I touch the chassis.
::::::
::::::
::::::Any ideas on where to start? Could I have made a mistake on a resistor or is something shorted?
::::::
::::::
::::::schematic here: http://www.nostalgiaair.org/Resources/888/M0024888.htm
::::::
::::::
If you can tune and pick up different stations the oscillator is operating. Sometimes just connecting a meter lead to the oscillator tube pin can cause it to stop. The meter lead adds capacity.
Check the antenna coil and other wiring/bandswitch leading up to top cap on the 6A8. Be sure you connect an antenna to the radio. Ten or 20 feet of wire will be enough.
Norm
:Yes the top of 6a8. I would not say it works prefect but it does pick up other stations if I tune while I touch the cap. I don't get negative voltage though.
:
:I recheck the antenna coil area.
:
::Tim
::
:: By cap do you mean top of the 6A8? If it picks up stations and tunes correctly it's not the 6A8 tube. If you hear one station across most of the band the oscillator isn't operating.
::
:: If the radio operates correctly while touching top of the 6A8 something in the antenna coil circuit is open.
::
::Norm
::
::
::
:::I checked all the nearby resistors and did not find anything out of spec or hooked up incorrectly. I will get a new tube and see if that is the issue. It's odd how well it plays when I touch the cap. Based on what I read, that most likely means a weak osc tube. Do you agree?
:::
::::Tim
::::
:::: Something is causing you oscillator not to operate giving negative grid voltage. Even though a 6A8 tests ok on a tester some will not oscillate in a circuit.
::::
:::: I would check resistors and voltages around this tube first. Pin #5, #6 and #8 make up the oscillator circuit on a 6A8.
::::
::::Norm
::::
:::::
::::
::::
::::Norm,
:::::
:::::I checked the continuity on the osc coil and it looks good. I double checked the 6a8 tube on my knight tester and it measures 70 and 75 on the two tests listed. I do get a hum on the 6q7 tube.
:::::
:::::Do you think it's the 6a8 tube or something else? I don't have a spare to test.
:::::
:::::Tim.
:::::
::::::Tim
::::::
:::::: Important to have pin #5 on your 6A8 negative several volts in relation to pin #8. This shows the oscillator is operating.
::::::
:::::: Check the oscillator coil (10) for continuity and other components around this tube. Try another 6A8 if you have one.
::::::
:::::: Touching top of the 6Q7 you should hear a loud hum. If you hear this noise the audio section is ok. Don't worry about plate voltage (pin 3) reading on this tube. Voltage is supplied through a large value resistor (R8) and meters load it down differently. Older meaters will give lower readings.
::::::
:::::: AVC voltage will vary by signal strength going negative when a strong station is received.
::::::
::::::Norm
::::::
:::::::I'm a novice at this but learning the hardway.
:::::::
:::::::I recently recapped a zenith 5s127 as well as changed some out-of-spec resistors.
:::::::
:::::::
:::::::I am having trouble aligning and have weak reception/volume. Checking the pin voltages several are off significantly.
:::::::
:::::::
:::::::1st det/osc tube: pin 5 is +4.6, should be -1vdc; pin 6 is 204vdc,
:::::::should be 166vdc.
:::::::2nd det/AVC tube: pin 3 is 127vdc, should be 75vdc; pins 4&5 are
:::::::1.4vdc, should be 0.1.
:::::::
:::::::
:::::::Also top cap (pin 9) of 1st det/osc and IF tubes measure .4mvAC.
:::::::Should be 0. Top of 2nd det/AVC measures 1.1mvAC.
:::::::
:::::::
:::::::I get sound good sound when I touch the top osc cap with the volt meter (pick up station). Some weak sound if I touch the IF tube cap. Noise/hum if I touch the AVC tube cap. Volume fads significantly and voltage drops if I touch the chassis.
:::::::
:::::::
:::::::Any ideas on where to start? Could I have made a mistake on a resistor or is something shorted?
:::::::
:::::::
:::::::schematic here: http://www.nostalgiaair.org/Resources/888/M0024888.htm
:::::::
:::::::
Tim,
:Tim
:
: If you can tune and pick up different stations the oscillator is operating. Sometimes just connecting a meter lead to the oscillator tube pin can cause it to stop. The meter lead adds capacity.
:
: Check the antenna coil and other wiring/bandswitch leading up to top cap on the 6A8. Be sure you connect an antenna to the radio. Ten or 20 feet of wire will be enough.
:
:Norm
:
::Yes the top of 6a8. I would not say it works prefect but it does pick up other stations if I tune while I touch the cap. I don't get negative voltage though.
::
::I recheck the antenna coil area.
::
:::Tim
:::
::: By cap do you mean top of the 6A8? If it picks up stations and tunes correctly it's not the 6A8 tube. If you hear one station across most of the band the oscillator isn't operating.
:::
::: If the radio operates correctly while touching top of the 6A8 something in the antenna coil circuit is open.
:::
:::Norm
:::
:::
:::
::::I checked all the nearby resistors and did not find anything out of spec or hooked up incorrectly. I will get a new tube and see if that is the issue. It's odd how well it plays when I touch the cap. Based on what I read, that most likely means a weak osc tube. Do you agree?
::::
:::::Tim
:::::
::::: Something is causing you oscillator not to operate giving negative grid voltage. Even though a 6A8 tests ok on a tester some will not oscillate in a circuit.
:::::
::::: I would check resistors and voltages around this tube first. Pin #5, #6 and #8 make up the oscillator circuit on a 6A8.
:::::
:::::Norm
:::::
::::::
:::::
:::::
:::::Norm,
::::::
::::::I checked the continuity on the osc coil and it looks good. I double checked the 6a8 tube on my knight tester and it measures 70 and 75 on the two tests listed. I do get a hum on the 6q7 tube.
::::::
::::::Do you think it's the 6a8 tube or something else? I don't have a spare to test.
::::::
::::::Tim.
::::::
:::::::Tim
:::::::
::::::: Important to have pin #5 on your 6A8 negative several volts in relation to pin #8. This shows the oscillator is operating.
:::::::
::::::: Check the oscillator coil (10) for continuity and other components around this tube. Try another 6A8 if you have one.
:::::::
::::::: Touching top of the 6Q7 you should hear a loud hum. If you hear this noise the audio section is ok. Don't worry about plate voltage (pin 3) reading on this tube. Voltage is supplied through a large value resistor (R8) and meters load it down differently. Older meaters will give lower readings.
:::::::
::::::: AVC voltage will vary by signal strength going negative when a strong station is received.
:::::::
:::::::Norm
:::::::
::::::::I'm a novice at this but learning the hardway.
::::::::
::::::::I recently recapped a zenith 5s127 as well as changed some out-of-spec resistors.
::::::::
::::::::
::::::::I am having trouble aligning and have weak reception/volume. Checking the pin voltages several are off significantly.
::::::::
::::::::
::::::::1st det/osc tube: pin 5 is +4.6, should be -1vdc; pin 6 is 204vdc,
::::::::should be 166vdc.
::::::::2nd det/AVC tube: pin 3 is 127vdc, should be 75vdc; pins 4&5 are
::::::::1.4vdc, should be 0.1.
::::::::
::::::::
::::::::Also top cap (pin 9) of 1st det/osc and IF tubes measure .4mvAC.
::::::::Should be 0. Top of 2nd det/AVC measures 1.1mvAC.
::::::::
::::::::
::::::::I get sound good sound when I touch the top osc cap with the volt meter (pick up station). Some weak sound if I touch the IF tube cap. Noise/hum if I touch the AVC tube cap. Volume fads significantly and voltage drops if I touch the chassis.
::::::::
::::::::
::::::::Any ideas on where to start? Could I have made a mistake on a resistor or is something shorted?
::::::::
::::::::
::::::::schematic here: http://www.nostalgiaair.org/Resources/888/M0024888.htm
::::::::
::::::::
:Tuning does not seem to be real tight. For example, one station at 550 is picked up over a range from 530 to about 600. it is a strong station but that seems excessive. Does that mean a potentially weak tube? I'm going to get a new one anyway to see if it makes a difference along with the checks you suggest.
:
:Tim,
:
::Tim
::
:: If you can tune and pick up different stations the oscillator is operating. Sometimes just connecting a meter lead to the oscillator tube pin can cause it to stop. The meter lead adds capacity.
::
:: Check the antenna coil and other wiring/bandswitch leading up to top cap on the 6A8. Be sure you connect an antenna to the radio. Ten or 20 feet of wire will be enough.
::
::Norm
::
:::Yes the top of 6a8. I would not say it works prefect but it does pick up other stations if I tune while I touch the cap. I don't get negative voltage though.
:::
:::I recheck the antenna coil area.
:::
::::Tim
::::
:::: By cap do you mean top of the 6A8? If it picks up stations and tunes correctly it's not the 6A8 tube. If you hear one station across most of the band the oscillator isn't operating.
::::
:::: If the radio operates correctly while touching top of the 6A8 something in the antenna coil circuit is open.
::::
::::Norm
::::
::::
::::
:::::I checked all the nearby resistors and did not find anything out of spec or hooked up incorrectly. I will get a new tube and see if that is the issue. It's odd how well it plays when I touch the cap. Based on what I read, that most likely means a weak osc tube. Do you agree?
:::::
::::::Tim
::::::
:::::: Something is causing you oscillator not to operate giving negative grid voltage. Even though a 6A8 tests ok on a tester some will not oscillate in a circuit.
::::::
:::::: I would check resistors and voltages around this tube first. Pin #5, #6 and #8 make up the oscillator circuit on a 6A8.
::::::
::::::Norm
::::::
:::::::
::::::
::::::
::::::Norm,
:::::::
:::::::I checked the continuity on the osc coil and it looks good. I double checked the 6a8 tube on my knight tester and it measures 70 and 75 on the two tests listed. I do get a hum on the 6q7 tube.
:::::::
:::::::Do you think it's the 6a8 tube or something else? I don't have a spare to test.
:::::::
:::::::Tim.
:::::::
::::::::Tim
::::::::
:::::::: Important to have pin #5 on your 6A8 negative several volts in relation to pin #8. This shows the oscillator is operating.
::::::::
:::::::: Check the oscillator coil (10) for continuity and other components around this tube. Try another 6A8 if you have one.
::::::::
:::::::: Touching top of the 6Q7 you should hear a loud hum. If you hear this noise the audio section is ok. Don't worry about plate voltage (pin 3) reading on this tube. Voltage is supplied through a large value resistor (R8) and meters load it down differently. Older meaters will give lower readings.
::::::::
:::::::: AVC voltage will vary by signal strength going negative when a strong station is received.
::::::::
::::::::Norm
::::::::
:::::::::I'm a novice at this but learning the hardway.
:::::::::
:::::::::I recently recapped a zenith 5s127 as well as changed some out-of-spec resistors.
:::::::::
:::::::::
:::::::::I am having trouble aligning and have weak reception/volume. Checking the pin voltages several are off significantly.
:::::::::
:::::::::
:::::::::1st det/osc tube: pin 5 is +4.6, should be -1vdc; pin 6 is 204vdc,
:::::::::should be 166vdc.
:::::::::2nd det/AVC tube: pin 3 is 127vdc, should be 75vdc; pins 4&5 are
:::::::::1.4vdc, should be 0.1.
:::::::::
:::::::::
:::::::::Also top cap (pin 9) of 1st det/osc and IF tubes measure .4mvAC.
:::::::::Should be 0. Top of 2nd det/AVC measures 1.1mvAC.
:::::::::
:::::::::
:::::::::I get sound good sound when I touch the top osc cap with the volt meter (pick up station). Some weak sound if I touch the IF tube cap. Noise/hum if I touch the AVC tube cap. Volume fads significantly and voltage drops if I touch the chassis.
:::::::::
:::::::::
:::::::::Any ideas on where to start? Could I have made a mistake on a resistor or is something shorted?
:::::::::
:::::::::
:::::::::schematic here: http://www.nostalgiaair.org/Resources/888/M0024888.htm
:::::::::
:::::::::
A 6D8 can be used in place of 6A8 in your radio.
When the oscillator doesn't operate a radio will not tune in different stations. It can pick up strong local station(s) that get louder or softer as you tune.
Norm
:Can I subsitute a 6D8 tube in place of 6A8? I have one of those. The tube sub table has an asterisk.
:
::Tuning does not seem to be real tight. For example, one station at 550 is picked up over a range from 530 to about 600. it is a strong station but that seems excessive. Does that mean a potentially weak tube? I'm going to get a new one anyway to see if it makes a difference along with the checks you suggest.
::
::Tim,
::
:::Tim
:::
::: If you can tune and pick up different stations the oscillator is operating. Sometimes just connecting a meter lead to the oscillator tube pin can cause it to stop. The meter lead adds capacity.
:::
::: Check the antenna coil and other wiring/bandswitch leading up to top cap on the 6A8. Be sure you connect an antenna to the radio. Ten or 20 feet of wire will be enough.
:::
:::Norm
:::
::::Yes the top of 6a8. I would not say it works prefect but it does pick up other stations if I tune while I touch the cap. I don't get negative voltage though.
::::
::::I recheck the antenna coil area.
::::
:::::Tim
:::::
::::: By cap do you mean top of the 6A8? If it picks up stations and tunes correctly it's not the 6A8 tube. If you hear one station across most of the band the oscillator isn't operating.
:::::
::::: If the radio operates correctly while touching top of the 6A8 something in the antenna coil circuit is open.
:::::
:::::Norm
:::::
:::::
:::::
::::::I checked all the nearby resistors and did not find anything out of spec or hooked up incorrectly. I will get a new tube and see if that is the issue. It's odd how well it plays when I touch the cap. Based on what I read, that most likely means a weak osc tube. Do you agree?
::::::
:::::::Tim
:::::::
::::::: Something is causing you oscillator not to operate giving negative grid voltage. Even though a 6A8 tests ok on a tester some will not oscillate in a circuit.
:::::::
::::::: I would check resistors and voltages around this tube first. Pin #5, #6 and #8 make up the oscillator circuit on a 6A8.
:::::::
:::::::Norm
:::::::
::::::::
:::::::
:::::::
:::::::Norm,
::::::::
::::::::I checked the continuity on the osc coil and it looks good. I double checked the 6a8 tube on my knight tester and it measures 70 and 75 on the two tests listed. I do get a hum on the 6q7 tube.
::::::::
::::::::Do you think it's the 6a8 tube or something else? I don't have a spare to test.
::::::::
::::::::Tim.
::::::::
:::::::::Tim
:::::::::
::::::::: Important to have pin #5 on your 6A8 negative several volts in relation to pin #8. This shows the oscillator is operating.
:::::::::
::::::::: Check the oscillator coil (10) for continuity and other components around this tube. Try another 6A8 if you have one.
:::::::::
::::::::: Touching top of the 6Q7 you should hear a loud hum. If you hear this noise the audio section is ok. Don't worry about plate voltage (pin 3) reading on this tube. Voltage is supplied through a large value resistor (R8) and meters load it down differently. Older meaters will give lower readings.
:::::::::
::::::::: AVC voltage will vary by signal strength going negative when a strong station is received.
:::::::::
:::::::::Norm
:::::::::
::::::::::I'm a novice at this but learning the hardway.
::::::::::
::::::::::I recently recapped a zenith 5s127 as well as changed some out-of-spec resistors.
::::::::::
::::::::::
::::::::::I am having trouble aligning and have weak reception/volume. Checking the pin voltages several are off significantly.
::::::::::
::::::::::
::::::::::1st det/osc tube: pin 5 is +4.6, should be -1vdc; pin 6 is 204vdc,
::::::::::should be 166vdc.
::::::::::2nd det/AVC tube: pin 3 is 127vdc, should be 75vdc; pins 4&5 are
::::::::::1.4vdc, should be 0.1.
::::::::::
::::::::::
::::::::::Also top cap (pin 9) of 1st det/osc and IF tubes measure .4mvAC.
::::::::::Should be 0. Top of 2nd det/AVC measures 1.1mvAC.
::::::::::
::::::::::
::::::::::I get sound good sound when I touch the top osc cap with the volt meter (pick up station). Some weak sound if I touch the IF tube cap. Noise/hum if I touch the AVC tube cap. Volume fads significantly and voltage drops if I touch the chassis.
::::::::::
::::::::::
::::::::::Any ideas on where to start? Could I have made a mistake on a resistor or is something shorted?
::::::::::
::::::::::
::::::::::schematic here: http://www.nostalgiaair.org/Resources/888/M0024888.htm
::::::::::
::::::::::
Now also I seem to be getting a motorboat sound in the middle of the AM tuning range.
:Tim
:
: A 6D8 can be used in place of 6A8 in your radio.
:
: When the oscillator doesn't operate a radio will not tune in different stations. It can pick up strong local station(s) that get louder or softer as you tune.
:
:Norm
:
::Can I subsitute a 6D8 tube in place of 6A8? I have one of those. The tube sub table has an asterisk.
::
:::Tuning does not seem to be real tight. For example, one station at 550 is picked up over a range from 530 to about 600. it is a strong station but that seems excessive. Does that mean a potentially weak tube? I'm going to get a new one anyway to see if it makes a difference along with the checks you suggest.
:::
:::Tim,
:::
::::Tim
::::
:::: If you can tune and pick up different stations the oscillator is operating. Sometimes just connecting a meter lead to the oscillator tube pin can cause it to stop. The meter lead adds capacity.
::::
:::: Check the antenna coil and other wiring/bandswitch leading up to top cap on the 6A8. Be sure you connect an antenna to the radio. Ten or 20 feet of wire will be enough.
::::
::::Norm
::::
:::::Yes the top of 6a8. I would not say it works prefect but it does pick up other stations if I tune while I touch the cap. I don't get negative voltage though.
:::::
:::::I recheck the antenna coil area.
:::::
::::::Tim
::::::
:::::: By cap do you mean top of the 6A8? If it picks up stations and tunes correctly it's not the 6A8 tube. If you hear one station across most of the band the oscillator isn't operating.
::::::
:::::: If the radio operates correctly while touching top of the 6A8 something in the antenna coil circuit is open.
::::::
::::::Norm
::::::
::::::
::::::
:::::::I checked all the nearby resistors and did not find anything out of spec or hooked up incorrectly. I will get a new tube and see if that is the issue. It's odd how well it plays when I touch the cap. Based on what I read, that most likely means a weak osc tube. Do you agree?
:::::::
::::::::Tim
::::::::
:::::::: Something is causing you oscillator not to operate giving negative grid voltage. Even though a 6A8 tests ok on a tester some will not oscillate in a circuit.
::::::::
:::::::: I would check resistors and voltages around this tube first. Pin #5, #6 and #8 make up the oscillator circuit on a 6A8.
::::::::
::::::::Norm
::::::::
:::::::::
::::::::
::::::::
::::::::Norm,
:::::::::
:::::::::I checked the continuity on the osc coil and it looks good. I double checked the 6a8 tube on my knight tester and it measures 70 and 75 on the two tests listed. I do get a hum on the 6q7 tube.
:::::::::
:::::::::Do you think it's the 6a8 tube or something else? I don't have a spare to test.
:::::::::
:::::::::Tim.
:::::::::
::::::::::Tim
::::::::::
:::::::::: Important to have pin #5 on your 6A8 negative several volts in relation to pin #8. This shows the oscillator is operating.
::::::::::
:::::::::: Check the oscillator coil (10) for continuity and other components around this tube. Try another 6A8 if you have one.
::::::::::
:::::::::: Touching top of the 6Q7 you should hear a loud hum. If you hear this noise the audio section is ok. Don't worry about plate voltage (pin 3) reading on this tube. Voltage is supplied through a large value resistor (R8) and meters load it down differently. Older meaters will give lower readings.
::::::::::
:::::::::: AVC voltage will vary by signal strength going negative when a strong station is received.
::::::::::
::::::::::Norm
::::::::::
:::::::::::I'm a novice at this but learning the hardway.
:::::::::::
:::::::::::I recently recapped a zenith 5s127 as well as changed some out-of-spec resistors.
:::::::::::
:::::::::::
:::::::::::I am having trouble aligning and have weak reception/volume. Checking the pin voltages several are off significantly.
:::::::::::
:::::::::::
:::::::::::1st det/osc tube: pin 5 is +4.6, should be -1vdc; pin 6 is 204vdc,
:::::::::::should be 166vdc.
:::::::::::2nd det/AVC tube: pin 3 is 127vdc, should be 75vdc; pins 4&5 are
:::::::::::1.4vdc, should be 0.1.
:::::::::::
:::::::::::
:::::::::::Also top cap (pin 9) of 1st det/osc and IF tubes measure .4mvAC.
:::::::::::Should be 0. Top of 2nd det/AVC measures 1.1mvAC.
:::::::::::
:::::::::::
:::::::::::I get sound good sound when I touch the top osc cap with the volt meter (pick up station). Some weak sound if I touch the IF tube cap. Noise/hum if I touch the AVC tube cap. Volume fads significantly and voltage drops if I touch the chassis.
:::::::::::
:::::::::::
:::::::::::Any ideas on where to start? Could I have made a mistake on a resistor or is something shorted?
:::::::::::
:::::::::::
:::::::::::schematic here: http://www.nostalgiaair.org/Resources/888/M0024888.htm
:::::::::::
:::::::::::
Yes you are probably tuning to a harmonic. I've seen this before. IF Transformers screws should be around a half turn from tight. When tuned to a harmonic they are all the way open. This could also give you motorboating.
Norm
:So I tried the 6D8 and the voltages on 5 dropped a couple volts below pin 8 (but not negative). However, I can't seem to get the IF tuned properly. I have to screw out the secondary adjustment on both cans all the way out and the primary's most of the way out to get it to tune in. Could I be tuning to a harmonic and missing the correct freq?
:
:Now also I seem to be getting a motorboat sound in the middle of the AM tuning range.
:
::Tim
::
:: A 6D8 can be used in place of 6A8 in your radio.
::
:: When the oscillator doesn't operate a radio will not tune in different stations. It can pick up strong local station(s) that get louder or softer as you tune.
::
::Norm
::
:::Can I subsitute a 6D8 tube in place of 6A8? I have one of those. The tube sub table has an asterisk.
:::
::::Tuning does not seem to be real tight. For example, one station at 550 is picked up over a range from 530 to about 600. it is a strong station but that seems excessive. Does that mean a potentially weak tube? I'm going to get a new one anyway to see if it makes a difference along with the checks you suggest.
::::
::::Tim,
::::
:::::Tim
:::::
::::: If you can tune and pick up different stations the oscillator is operating. Sometimes just connecting a meter lead to the oscillator tube pin can cause it to stop. The meter lead adds capacity.
:::::
::::: Check the antenna coil and other wiring/bandswitch leading up to top cap on the 6A8. Be sure you connect an antenna to the radio. Ten or 20 feet of wire will be enough.
:::::
:::::Norm
:::::
::::::Yes the top of 6a8. I would not say it works prefect but it does pick up other stations if I tune while I touch the cap. I don't get negative voltage though.
::::::
::::::I recheck the antenna coil area.
::::::
:::::::Tim
:::::::
::::::: By cap do you mean top of the 6A8? If it picks up stations and tunes correctly it's not the 6A8 tube. If you hear one station across most of the band the oscillator isn't operating.
:::::::
::::::: If the radio operates correctly while touching top of the 6A8 something in the antenna coil circuit is open.
:::::::
:::::::Norm
:::::::
:::::::
:::::::
::::::::I checked all the nearby resistors and did not find anything out of spec or hooked up incorrectly. I will get a new tube and see if that is the issue. It's odd how well it plays when I touch the cap. Based on what I read, that most likely means a weak osc tube. Do you agree?
::::::::
:::::::::Tim
:::::::::
::::::::: Something is causing you oscillator not to operate giving negative grid voltage. Even though a 6A8 tests ok on a tester some will not oscillate in a circuit.
:::::::::
::::::::: I would check resistors and voltages around this tube first. Pin #5, #6 and #8 make up the oscillator circuit on a 6A8.
:::::::::
:::::::::Norm
:::::::::
::::::::::
:::::::::
:::::::::
:::::::::Norm,
::::::::::
::::::::::I checked the continuity on the osc coil and it looks good. I double checked the 6a8 tube on my knight tester and it measures 70 and 75 on the two tests listed. I do get a hum on the 6q7 tube.
::::::::::
::::::::::Do you think it's the 6a8 tube or something else? I don't have a spare to test.
::::::::::
::::::::::Tim.
::::::::::
:::::::::::Tim
:::::::::::
::::::::::: Important to have pin #5 on your 6A8 negative several volts in relation to pin #8. This shows the oscillator is operating.
:::::::::::
::::::::::: Check the oscillator coil (10) for continuity and other components around this tube. Try another 6A8 if you have one.
:::::::::::
::::::::::: Touching top of the 6Q7 you should hear a loud hum. If you hear this noise the audio section is ok. Don't worry about plate voltage (pin 3) reading on this tube. Voltage is supplied through a large value resistor (R8) and meters load it down differently. Older meaters will give lower readings.
:::::::::::
::::::::::: AVC voltage will vary by signal strength going negative when a strong station is received.
:::::::::::
:::::::::::Norm
:::::::::::
::::::::::::I'm a novice at this but learning the hardway.
::::::::::::
::::::::::::I recently recapped a zenith 5s127 as well as changed some out-of-spec resistors.
::::::::::::
::::::::::::
::::::::::::I am having trouble aligning and have weak reception/volume. Checking the pin voltages several are off significantly.
::::::::::::
::::::::::::
::::::::::::1st det/osc tube: pin 5 is +4.6, should be -1vdc; pin 6 is 204vdc,
::::::::::::should be 166vdc.
::::::::::::2nd det/AVC tube: pin 3 is 127vdc, should be 75vdc; pins 4&5 are
::::::::::::1.4vdc, should be 0.1.
::::::::::::
::::::::::::
::::::::::::Also top cap (pin 9) of 1st det/osc and IF tubes measure .4mvAC.
::::::::::::Should be 0. Top of 2nd det/AVC measures 1.1mvAC.
::::::::::::
::::::::::::
::::::::::::I get sound good sound when I touch the top osc cap with the volt meter (pick up station). Some weak sound if I touch the IF tube cap. Noise/hum if I touch the AVC tube cap. Volume fads significantly and voltage drops if I touch the chassis.
::::::::::::
::::::::::::
::::::::::::Any ideas on where to start? Could I have made a mistake on a resistor or is something shorted?
::::::::::::
::::::::::::
::::::::::::schematic here: http://www.nostalgiaair.org/Resources/888/M0024888.htm
::::::::::::
::::::::::::