SVT-VT volume and noise problem, help!

[pontiacpete]

This amp has a couple of issues:
The volume is doing something weird, it doesn't go down all the way on the first channel. I swapped out the pot with the same results. The second channel works fine.
Also, there is a 120hz hum.

When plugging into the the 'amp in' the noise goes away. So I think the power amp is working properly.
I checked all the solder joints on the pre amp and the main board.

So the question is ,, is this a pre amp issue and if so where do I go from here? Scope? and trace?

[Jazz P Bass]

Well, if going into the "power amp in" does not produce the symptoms, I would have to say it is a preamp problem.
You could always prove it by taking the "peamp out" into another amp.
The easiest place to start in the preamp is the tubes.

[pontiacpete]

I ran the pre amp out to another power amp and the same problem.

Turns out the electrolytic on the pre amp board went bad, replaced and problem solved

Thanks Jazz P bass
pete

[Jazz P Bass]

Glad to hear that you got it solved, Pete.