This is my first integrated tube amp so I don’t know much of the lingo like “hum pot” and “death cap” but this is the type of info I need! Which brand did you use for the tubes?
- Hum pot is an adjuster control located underneath about in the middle of the board. Look for R5A in the schematic.
- Only brand I'm aware of that makes the spiral wound tube is Sovtek. All other tubes are TAD.
- The "death cap" is the large capacitor attached to ground from the power switch. An example ...
Another trick to try - attach a ground wire between your input sources and the HF. That can help a lot. If there's no ground posts, any screw to each metal chassis will work. Also (if possible) try balancing the load from your input if it's got an output adjustment. My DAC was overpowering the Eico and creating strangeness probably similar to what you're hearing, but turning the DAC down a few notches and adding a ground wire did the trick.
PS - Have you tried the different inputs? Not uncommon for folk to convert those to make the unit more flexible with today's equipment, and not uncommon for them to get it wrong. My TAPE HEAD input was already converted for line level when I got it, and is actually cleaner than the stock AUX for my DAC.
And ya, recapping can get interesting. I couldn't find a multicap short enough to fit, so I went with separate caps under the board. New caps are much smaller, so plenty of room. That gave me some hum, but moving the cap leads a bit here and there solved that problem. It's also not uncommon for folk to "stuff" the old cap can by cutting the cover off and basically stuffing matching separate caps inside the can. And yes, that can be a bit of a crapshoot in the wrong hands. Done right though, such a repair is electronically the same and can be hard to spot.
Short version - don't expect that going with the classic stuff is gonna be easy sometimes. Worth the effort though, as you're looking at some mighty good sound once you get it right.
