Peavey Studio Pro 50 troubleshooting

[The Guitar]

Here's the low down on it. Dropped it off for a low volume and saturation issues. They fixed the low volume via replacing a bad cap, but could not figure out the saturation problem. They chatted with Peavey to no avail as they no longer have the parts there. Here's the saturation problem; when turning the saturation knob, it gets very fizzy/muddy. I've swapped speakers to eliminate that possiblity. I've looked up and down the board but don't see any cap leakage or burns and no broken solder joints. I've swapped out op amp chips, changed the power transistors with no luck. Needless to say, we are stumped. If anyone has ideas/info, it's appreciated.

 

[JamesPaul]

I maintain and repair my own. I spend time on the Peavey Forum as well. While I have the formal education, unless it is an issue I have seen before, I have to get the schematic, my DMM, my signal generator, and my scope, then go track it down. Let me PM you.