I haven’t updated, as I’m not sure if the problem is still there. I re-biased the driver tubes - they hadn’t drifted too far; about 12V plate voltage difference on each differential pair with CCS tail. I gave the volume pot another deOxit treatment at this time too. Since doing this I’ve had a couple 2+ hour listening sessions with no issues whatsoever.
I do need to tear the whole thing down to paint the top plate of the amp, so I’ll get some more testing in before that to decide if I want to resolder everything. I do have a scope, but need to get a transformer to float the amp (or disconnect the ground loop breaker diodes I suppose - everything should be floating after the PT that way)
There’s lots of wiring to check. Thanks again for all the helpful insights!
I do need to tear the whole thing down to paint the top plate of the amp, so I’ll get some more testing in before that to decide if I want to resolder everything. I do have a scope, but need to get a transformer to float the amp (or disconnect the ground loop breaker diodes I suppose - everything should be floating after the PT that way)
There’s lots of wiring to check. Thanks again for all the helpful insights!
