Yup, I'm familiar. It has the muting level pot. I'll head downstairs at some point today and pull the schematic...never dealt with this issue though. But it is common on well, everything that old.
Static could mean the amp is still working, you just lost signal somewhere. Probably an electrolytic cap went poof, that would correlate with the pop.
If you feel comfortable, open it up. Should be four screws on the bottom and the metal case will slide off the back. If it was an electrolytic you would visually see signs of soot on the bad cap, it might oven be split open.ha. might also have soot on the case above it, treasure map to the component.
Have you tried all the inputs to see if you get anything from the others? Were you on the tuner when it went? Or the tape input?
Honestly though, if I were you and not looking to go deep into a project like this,Just go with the guy. It's a serviceable reciever and I'm certain that you won't have any issues getting somebody locally...well, more locally than me anyway. : )