I'm having an issue with my Peavey Butcher that it just developed in the last couple days. Most of the time it appears to sound fine, but occasionally the output will become very weak. There is a loud buzz when this happens and I'm not playing, and when I am playing the volume is low and the sound is weak and distorted, and it sounds like there is a weird overtone under most notes, almost like a ring modulator. I've tried different guitars, cables, speakers, and power tubes and it continues to react the same way.
I can sometimes make the problem start by giving it a whack on the chassis near the preamp board and power transformer. However, this same technique does not make it go away. Turning the amp to standby and then back on again usually returns it to normal operation, for a while. This makes me suspect a bad connection. Although nothing is visibly loose or cracked, I plan on reflowing all the solder joints on the preamp and power supply boards, basically all things near where I can hit the amp to make it start sounding bad, as well as subbing in new preamp tubes. If this doesn't help then I'm not really sure what to try next. Any ideas for where to look given these symptoms?
Also schematic if it helps:
peavey-butcher.pdf
I can sometimes make the problem start by giving it a whack on the chassis near the preamp board and power transformer. However, this same technique does not make it go away. Turning the amp to standby and then back on again usually returns it to normal operation, for a while. This makes me suspect a bad connection. Although nothing is visibly loose or cracked, I plan on reflowing all the solder joints on the preamp and power supply boards, basically all things near where I can hit the amp to make it start sounding bad, as well as subbing in new preamp tubes. If this doesn't help then I'm not really sure what to try next. Any ideas for where to look given these symptoms?
Also schematic if it helps:
peavey-butcher.pdf
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