To me $100 for a broken radio is way too much.
As to the problem its probably a tube.
BUT this thing is German & they did some weird things like
have a drive mech for the vol control. Schematics can also
be hard to find. They can be a bitch to work on but every one
I saw always had great sound. If you havent yet restore
one of the big 50's-early 60's Zenith AM-FM radios. They are cheap
& sound as good. Only bad thing with them is if the IF transformers
have silver-mica disease.
73 Zeno
LFOD !