Ultimately, I ended up saving my spare change for a couple months and got the Trek II EIS-9V relay. Put it in a nice tidy box where the amp chassis used to live, wired a diode into my existing switch (as directed by Michael at Trek II), and away we go.

The bassist in my band and I were trying to build something similar to the EIS-9V on our own, but realized that it was just going to take up precious time we could spend PLAYING. That is the point of all of this after all, at least to me it is. Gotta maximize what little time is leftover after day jobs, family, and all that other fun stuff.

Anyway, I'm happy with the EIS and the fact that I won't have to be gigging with that sketchy mains switch I rigged up! Maybe someday when I have time I'll figure out what was wrong with the original amp.

Who am I kidding? I'll probably spend that time playing!