07-23-2022, 04:30 PM
First off, SMD typically affects AM and has popping or loud, intermittent static symptoms. (No static on FM - Steely Dan)
Double check part 85, 5 mfd 50 volt electrolytic cap. The negative must be connected to pin 3 and positive to pin 4 (B-) of the 12H6. This can be a 4.7mfd or 5mfd cap, nothing else.
If you don't have an FM generator an AM generator will do in a pinch. Just use an unmodulated 10.7MHz carrier to the FM antenna with a high impedance meter attached to 6AQ6 pin 6 to read a negative voltage. This voltage is the AGC voltage and varies depending on signal strength, which can be changed from the signal generator. If you get the AGC to vary with signal strength from the antenna the FM oscillator is probably not working. Otherwise one of the FM tubes may be bad; it's been my experience the FM RF amplifier. Double check any parts you replaced in the FM section. Do not change any of the settings until after you find and fix the culprit.
Double check part 85, 5 mfd 50 volt electrolytic cap. The negative must be connected to pin 3 and positive to pin 4 (B-) of the 12H6. This can be a 4.7mfd or 5mfd cap, nothing else.
If you don't have an FM generator an AM generator will do in a pinch. Just use an unmodulated 10.7MHz carrier to the FM antenna with a high impedance meter attached to 6AQ6 pin 6 to read a negative voltage. This voltage is the AGC voltage and varies depending on signal strength, which can be changed from the signal generator. If you get the AGC to vary with signal strength from the antenna the FM oscillator is probably not working. Otherwise one of the FM tubes may be bad; it's been my experience the FM RF amplifier. Double check any parts you replaced in the FM section. Do not change any of the settings until after you find and fix the culprit.
