What a rookie mistake… My variac is grounded… I’ve gotten too spoiled by working on a lot of isolated 24VAC circuits lately… One little check with the scope and boom. PCB death… So much for my one-of-kind short cut. I suppose I need to invest in one of those sets of isolated probes. Silver lining is I didn’t let the smoke out of the front-end of my tektronix scope.
I’ve got this burning CARD Is it possible to repair or how I can buy another
From York/Johnson Controls you can buy one. Sometimes local service shops will have a spare used one, I recommend starting there.