while the relays are running, the 5v that powers them stays steady.
   i'm guessing I shorted something that overvolted or reverse polarized
   them. ground and 12v were both exposed, so shorting that could have
   given them -7V.
   I try not to leave things exposed like that when working. I tricked
   myself by thinking it was okay to leave ground exposed, then working on
   12V leaving it briefly exposed, while it was powered. two mistakes at
   once.