So my pops bought this head for me brand new back in the early 90’s when I was a kid and so it holds some sentimental value to me. Because of this, I am up for the challenge to try and fix it myself. When I first got it I used it for 3-4 years problem free then it suddenly stopped producing sound. Never blew fuses, no hum, always powered up but just silent. So decades later after recently building a MojoTone Super Reverb, and recapping some McIntosh power amps, I’m facing my greatest challenge to date, trying to fix this. I brought it up on a variac with no speaker hooked up and everything seemed ok. Replaced the one 12ax7 in it. Then hooked up a speaker and the speaker pulled in and out repeatedly and had a loud hum. So ordered up the 4700uf 50v filter caps and a few others on the power amp board and replaced. Nothing changed, as soon as I get to about 5 volts on the variac I can hear an electronic hum coming out of the speaker so I have not put full power with a speaker attached since, as I’m nervous about ruining the speaker. Before changing the filter caps I hooked up a signal gen from my phone and put the oscilloscope on the speaker output with a dummy load and was able to get an ok wave but was inconsistent or intermittent. So I’m basically asking anyone out there that may have worked on this particular era of amps for any insight or direction to try and get her singing again. Thanks in advance!!