Thanks for the reply. I have checked everything I know how to check and can not identify the problem. I guess I will have to take it to the shop.

I have a VOX AD50VT that suddenly stopped working. Everything was fine at a friends house but when I took the amp home and turned it on it had a terrible hum. None of the controls have any effect on the noise. This amp has 1 12ax7 pre-amp tube so I swapped it with a known good one but that had no effect either. Before I tear into this thing does anyone have any suggestions on what the problem may be?

I have a Crate GFX-1200H that will only produce a hissing sound, nothing else. Does anyone have a schematic for this head or know where I can find one?