I was jangled awake dark and early one spring morning by my bedside telephone. The main transmitter was off the air, the backup was on, and oh yeah, the smoke alarm at the transmitter site is alarming. Hour drive to the site, but the backup stayed on-air for the whole trip, so the building's probably not burning down. No flash fire when I opened the building door, so that's good.
When I entered the transmitter building, my first thought was "bar-b-que!" That was the weirdest smelling melted transformer or vented capacitor I'd ever encountered. Smelled a hell of a lot better than a fried selenium rectifier stack.
Start diagnosis with the power amplifier (4CX15000A tube) power supply, so I drop to my knees (aah, those were the days) in front of the PA rack, and begin unscrewing the panel screws. I moved the panel off to the side, and there he was; a two foot long copperhead! I stood up like a ninja!
I didn't really need to worry. Cool night, warm 22 kilovolt transformer. He crawled on top of the transformer and bridged the output terminals. He wasn't going to move again without help. So I helped. Cleaned up the mess, ran fans to ventilate the building, and got the main back on-air. But I never did figure out where he got into the building.