Jeez this amp is a pain. It came in with some oscillation, so i did a cap job. Yep, everything came out to get the board out with all the pots hanging off it, put it back and it was fine. Except no reverb. That turned out to be the opamp, unusually, and I managed to replace it without taking the damn board out again .
I was bench-testing it and suddenly the volume dropped. Traced this to the J175 P-channel fet on the bottom left of the FX loop page on the attached schems. I assumed this was there to effect the mute, but weirdly the speaker mute switch still muted the amp without it. Well I replaced it with an BF245A and the volume came back... and now the amp makes a loud pop when channel switching. It pops on all channels and also when disengaging the reverb with the footswitch (but not when engaging the reverb). It pops with the footswitch unplugged and you use the switch on the back channel to change channels. It's a really loud pop... I took out the BF245A and it still pops without it.
I'm out of patience so I'm off to eat. If anyone can save me the trouble of trying to work out what's up with the damn cursed godforsaken thing now, or indeed what I have done to f it up, I would be grateful beyond words!
Sometimes it's so nice to know you're all out there, guys
I was bench-testing it and suddenly the volume dropped. Traced this to the J175 P-channel fet on the bottom left of the FX loop page on the attached schems. I assumed this was there to effect the mute, but weirdly the speaker mute switch still muted the amp without it. Well I replaced it with an BF245A and the volume came back... and now the amp makes a loud pop when channel switching. It pops on all channels and also when disengaging the reverb with the footswitch (but not when engaging the reverb). It pops with the footswitch unplugged and you use the switch on the back channel to change channels. It's a really loud pop... I took out the BF245A and it still pops without it.
I'm out of patience so I'm off to eat. If anyone can save me the trouble of trying to work out what's up with the damn cursed godforsaken thing now, or indeed what I have done to f it up, I would be grateful beyond words!
Sometimes it's so nice to know you're all out there, guys
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