Yep, so it was a bad diode. I got the replacements today, 30 seconds with the iron later and wonderful music is playing through my Sextetts. Thanks guys.
(https://forum.bottlehead.com/proxy.php?request=http%3A%2F%2Fcdn.head-fi.org%2F9%2F9d%2F1000x500px-LL-9d5b2f3e_IMG_5200.JPG&hash=d0e082486876b51feba92e3b9d35d9908991098e)
I'd like to think I'm pretty decent with a soldering iron, but man my painting could still use some work.
I used some of that hammered paint and even did the tops of the screws, but the finish came out... well, not as "hammered" as I wanted, though it does have a rather nice shimmer to it. I was thinking of spraying the bottom of the tube to match, but considering how hot it gets, I'm guessing that's a bad idea? (it only looks like the same colour in the picture due to reflection)
As for the wood base, let's say I made the very silly mistake of putting a semi-gloss poly coat on top of the gloss stain. Whoops. I was also trying to make it darker, but subsequent coats of stain didn't make it any darker. Should be there some sort of prep work done to the wood for deeper stains? I also sanded down to 600grit before staining; not sure if that makes any difference at all.