Good thoughts, and I've done about all of that, including cleaning all of the switches. I've got a brewery kit en route.
Right now, my frustration is with the sound. While is SOOO much better than it was, I can figure out why it keeps fading out.
Here's what I noticed this evening:
Turned it on after not having it on for a couple of days. Sound was GREAT....... for about 3-5 minutes. While playing Donkey Kong, I heard it fading, but it never fades completely. I put in Raiders, and it's the same thing. Tweak L201, and it's solid. So, I turn it off, unplug it, and go back to it after a few. Same thing. Good sound for 3-5 minutes, and then slowly fades.
Like I said, never fully dies off anymore, but I can't keep the level up. I've had to leave the cover off just so I can tweak L201 constantly.