The small 100pf caps are connected as they should, in series with a 30k resistor with the anode on one end, and the B+ on the other. I've double checked before, but just for the sake of it I did it again. As mentioned, all resistances are within a tolerance of 1%, and I've compared the components and wiring of the two channels multiple times.
Regarding those "death caps" - they are spanking new Y1s. The old ones were PIO.
Regarding those "death caps" - they are spanking new Y1s. The old ones were PIO.
I had an amplifier do that. There was a shorted turn in the primary of one of the OPTs and that side oscillated. I swapped OPTs on the two channels and the oscillation followed the OPT. Measuring primary inductance on the suspect OPT showed it up, because a shorted turn will clobber that, resulting in a low reading.