He was getting no sound at all upon failure. After I replaced and biased the outputs, I got sound, but some pretty nasty sputtery spitty distorted stuff. At this point, I've replaced all 3 filter caps, the volume pot(had a faulty one exhibit this behavior in the past in a pro jr), every coupling cap, speaker, and every tube. Gotta be the OT, right? Nope, stuck an Edcor in there real quick and no change.
I'm gonna check everything again, but all voltages looked solid, no funny business, screen Rs measure fine, as does every other resistor in the amp. Sockets are solid, any and all jiggling/chopsticking reveals nothing. I've also replaced the input and speaker jack. I have damn near rebuilt this amp.
To me it sounds like it's missing a reference to ground somewhere. Upon going down that route, I realized this amp has no circuit ground connection to chassis. That's fine but it's throwing me for a loop, as voltage reading across the 1st filter cap, on the board, reads 350VDC, but a reading from the + of the same cap to the chassi reads 345VDC, and I'm showing around 90K resistance from circuit ground to chassis??? Again, no continuity from any board ground to chassis. I slapped a wire from signal ground to chassis, and all it did was quiet some hum
The other thing that seems like it's come up in the past but I can't place it, is that when the amp gets turned off, everything sounds great and normal for that 3 seconds as the sound dies.
Any ideas?
