On a friend's Peavey-Musician, Series-400 bass head; at any volume other than the lowest low I get a high-pitched ring that increases with either gain or volume. I want to make it clear right now that this is not feedback. Sounds similar to some voltage leaks I've heard in the past where a bad electrolytic was leaking DC into the ground. Problem is, I can't find it. I don't have a capacitance meter and am without a scheme to see what values are supposed to be present in some of the worn down components.

The amp is solid state and high wattage with HUGE filter-caps, so I want to see if any-one has had this issue before before I blow up another cap-drain, lol

The two pics are of the amp itself to maybe jog a memory and of a component in the power-amp, RIGHT before the output, that i"m having trouble identifying. it's in pretty bad shape and if it's a choke I bet it's the culprit.

I'm replacing the infamous cardboard tube reverb tank in my Silvertone with a traditional spring box BUT I want to get it functioning the way it was intended first. I can physically knock the tank and get verb but playing doesn't actuate it.

I have one clue though: only one of the two coaxial leads that go to the tank has a decent audio signal, the other one is weak sounding ... I don't know, but I think both should be pretty hot, right?