Thanks @muchxs and everyone else for all of your patience and help, this is all great. I haven't had the chassis out of the cabinet in a while, but I recall that the power transformer actually had the fender logo on it. Later tonight when I have some time, I'll take the chassis out and get a picture of the transformers for everyone - I definitely need to check them out. - Filter caps grounding: I've asked myself the same question, and I am assuming that the builder stuck to the original schematic and there's a buss behind the board connecting them to the cathode resistor and the third cap to ground them. I'm afraid to take the board off, because then we're in full on rebuild territory - that might be a foregone conclusion at this point, though. I'll check continuity tonight and report back, thanks for this great idea. - Power Tubes: you can kind of see in one of the pictures that both are grounded directly to the chassis via an uninsulated wire running from pins 1 and 2. The original diagram does not have these grounds depicted - could this be an indicator that the filters are not grounded, and the builder relied on grounding the 6V6es to accomplish that? - Other power supply questions: one green lead from the PT (I'm assuming this is a 6.3V heater filament lead) goes to the pilot lamp, and the other one goes to the star ground on the chassis with the AC power cord and the red/yellow lead on the far left. I don't think this is the center tap, as there is a green/yellow lead that's been cut off and taped. Is it worth rerouting the lead from the star ground to the pilot lamp with the other lead and the heater filament? The rest of the PT leads - primary, HV, and 5V B+ - are all in the right place. It looks like what I assume is the HV center tap (red and yellow) is routed to the bypass switch, then to the star ground. There is another additional orange wire that is routed directly to the same ground. - The buzz/hum sound is whisper quiet but audible when the volumes are low. It gets louder as either volume increases, with some whooshing and fluttering flap flap flap sounds underneath, which makes me think it's the filters or a power supply issue. The amp has sat idle for long periods as well. You're absolutely right though, I should be using common sense and eliminating any easy grounding issues first. Thanks again for all of your patience and help. I'll be back with transformer pictures, voltage readings, and continuity results later.