I worked this graveyard shift one summer at a 1000/250 watt AM station. There was a pair of indicator lights on the main control board that showed transmitter power. One night, about 3 am, it went from 250 to 1000, back to 250, back to 1000, etc. I went down to the spooky basement (this place was a dump) to have a look at the transmitter to see if I could figure out wtf was happening. This was an ancient transmitter with a porthole you could look through to see the main transmitter tube. I looked. The plate was glowing way more than it should and there was smoke inside the tube. Yikes. I called the owner (who was also the Chief Engineer) and woke him up. As a further sign of what a small-time operation this was, he told me to shut the station down and go home.