For the most part all is well with my C-30 head. There are 2 problems, and I'm not sure where to start looking...

The Master knob seems to be not working. It will sometimes engage, but most of the time it is off even when pulled out. It does come on once in a while, but it is very random. It does not come on when I move the knob back and fourth, so it does not sound like something is loose. Its connections are very good. When it does work, it only changes the sound up to about 11:00 My first guess is that the switch is bad. Is there anything else that I should worry about or check?

This is my first amp build, so any help or advice would be great.

Thanks. Anthony