Robin: The dim bulb tester seems pretty straightforward. I think you’re right, this is a cheap way to avoid replacing expensive components.

Can you say more (or link to relevant information) about testing grounds and voltages with a meter? I’ve fussed around with a meter checking speaker impedances, but how would one go about using it in an amp?

I realize this can be dangerous. I think what I’ll do is start with a dim bulb test and if there is an issue, bring it to my tech to troubleshoot.