Mystery smoke from gauge cluster

So I had the gauge cluster in my 65 dart out to clean up some aftermarket wiring and bridge the ammeter, and while testing it I smelled something burning and a puff of smoke from what seems like the inside of the Guage cluster around the fuel Guage. I cut the power immediately and inspected the board but I can't see any damage or dark spots at all. When it happened I had the gauge cluster out of the dash on the harnesses, is it possible that it wasn't grounded and that was causing the issue? I noticed the gas gauge was moving when powered was turned on, but my lights dash lights were out.