Precisely. A "megger" test would reveal insulation break down that would
not be detectable with an ordinary VOM. Perhaps you could borrow, or
rent, a megger and take it to your location. It is more than a little
disconcerting to hear a gun-shot like "crack" coming from a RPC you
already have a lot of time and money invested in.

Aargh! I saw one of those cheap on eBay last year, but didn't bid as I
didn't think I had a use for it. I bet they're expensive pieces of kit
normally. What does the hand-cranked megger actually do? I'll keep an eye
out for one. Maybe another will turn up on eBay...

Basically they are ohmmeters for reading "leakage" resistance such as found
in motors, transformers and other devices with coils of wire.

Bob Swinney