#1
So, a while back I bought a used Powerball. It worked fine at first, but lately it's been driving me insane.

At first it was making a bunch of feedback and whistling noises. Someone told me I probably had a bad preamp tube, so I changed the right one and that problem was solved.

Shortly after I finally got a used 412 cab for it. When I got everything set up to jam with my band, the amp started giving me a ton of feedback whenever the other guitarist in my band would play. We tried moving the amps apart from each other, as well as having me standing really far away from both. It still feedbacks for some reason.

So I take everything home, thinking I can at least enjoy the amp by myself for now. I get it set up in my room, turn it on, and... the volume is screwed up. No matter how loud I crank it, it still stays at a quiet bedroom level. The volume level also sort of phases in and out.

I could really, really use some advice here.
Your body has parts your country can spare! By the way son, here's your wheelchair!
#2
It sounds like a bad diode with the volume.
I don't remember where I was,
When I realized life was a game.
The more seriously I took things,
The harder the rules became.
#3
replace all your tubes. maybe have a tech go through and check to make sure all the connections and wires don't have shorts in them first though. if that doesn't work then i don't know?
#5
Ok, so I just tried it again and now the volume seems to be working. I'm so confused.
Your body has parts your country can spare! By the way son, here's your wheelchair!