[mopar55]

Hi my name is Paul, I and new to this hobby, I have been a ham for 25 years so I have somewhat a background to radio.My call is KA9UMG. I am working on a Philco No. 81, the radio work with a hum, I change the filter capacitors on the power supply and that took care of the hum.It sounds very good but once in a while the audio will fade away and if you let it set for about a minute it will pop back on, or if you play with the volume or frequency switch I will go back on. I clean both with detox solution but it still happens. Can someone lead me in the right direction.
Thank You
Paul KA9UMG

[Radioroslyn]

Hi Paul and welcome!
As you can tell by the schematic this thing is a superhet with a regenerative detector. every part in this thing has to be on the money in order for it to work properly. Mostly the high value resistors in the detector circuit and the bypass caps. Also it's very common for the osc feedback winding to go open. If you pull it out look at the winding at the bottom of the coil if you see any green it's time to rewind. 25t of 32to38g wire will work fb. Check chassis ground connections too. You can also search this site for models 57,80,81,600,84,37-84,37-600 and Philco Jr. All have this same sort of circuit.
Guk lk om
de N3GTE
Terry