Heater Center Tap resistors Popping

[talbany]

Yeah honestly when they first popped I thought the OT failed. And then when I measured the heater voltages I got 90vac referenced to ground but when I lifted the pt heater wires I only got 7vac and I was like what the hell...lol

1.The high heater voltage could be due to capacitive coupling between the windings. That should go away once the filament winding has a ground reference.
2 To get a true reading on the filaments put one probe on one socket filament pin and the other probe on the other socket filament pin, never from chassis to one socket pin..
3 It's still possible an arc occurred inside the OPT? If it starts blowing fuses at high volumes after you get your load working again could be your insulation in the transformers primary has been compromised.Lets hope not!!

BTW..The problem with flyback diodes is if they happen to fail without you knowing, and then you're left wondering why the amp doesn't sound good. Another point of failure

Tony

[Goldguitarguy]

I ran the amp up this evening with the speaker cab hooked up and a guitar plug in. The clean channel I had both the volume and master at 10, no issues and it was surprisingly quiet. Drive channel with all knobs at 10 I started getting some very high frequency oscillation sitting on top of some feedback from the guitar when the master reached around 4-5 mark. I compared it to my sound generator and it was just under 12khz. Almost at the point where I couldn’t hear it. Im thinking it’s probably my lead dress which isn’t spectacular but could be a multitude of things I suppose.