Okay. Pretend I have a multimeter but that I have no idea where to stick the pointy bits. I gather that one end should be at that cap you described (either side's lead?), but where should the other go?

Also, are you saying that problem the first is that the empeg's power supply might be marginal and it's causing it to blow the tube (or that the tube's not actually bad, but just not being powered properly) and that problem the second is just a bad tube? Given that I've had two go bad, and not too many people have complained about that, the probability is that it's problem the first, right? I mean, I'll still check it, but if you have some definitive notion that that's the problem, especially given that it's reparable, that'd be super.