I bought this several months ago and shotgun recapped it, since almost all the paper caps were split open.
worked fine for about 5 minutes or so, then started acting up, with
garbled audio and only being able to sort of tune one station, but when
you would stop moving the tuning dial it would lose the station or at
least that's what it sounded like.
Months pass and I let it sit
on a shelf, today I decided to start anew. I went throught the radio and
checked the resistors, replaced a few out of spec. I thought maybe the
problem was with the oscillator so I replaced a 47pf cap related to
that. cleaned the 12sk7 and 12sa7 sockets, freed up a trimmer cap that
was a little rusted. changed out the antenna wires, tried a different
antenna, but nothing really made a difference.
then... I was
going through the radio with my signal tracer, and not really being able
to trace an RF signal I decided to make sure the AF was working, I was
getting the same audio from the signal tracer as I got from the radio,
until I placed the probe on the center pin of the volume control. All of
a sudden I got clear audio from both the signal tracer AND the radio,
AND the tuning started working. If I removed the ground wire of the
signal tracer from the radio chassis and touched the center pin of the
volume pot it went back to the way it was.
I spent most of the day working on it, and after replacing all of the original mica caps, I found that if I placed a resistor to ground in certain places the audio would return. I thought about this for a while and realized that all the components in question went through the volume pot to ground.
I pulled the volume pot and opened it up, this is what I found.
I did not think I had one so I took a break and went over to my brothers house for a while.
When I came back I looked though my stash of pots with switches and low and behold I had the exact replacement a 500k pot, with a switch AND a 100k tap.
I installed it and it work fine.
The last problem was that the original speaker was trashed.
I found a usable speaker, drilled the bracket off the back of the old speaker, attached it to the new one and mounted the speaker.
I repainted the sides and did an alignment.