That specific whistle at a certain temp is such a weird one. I've seen fans with a bad bearing make noise at all speeds, but that temp trigger makes me wonder about the fan's control circuit. Could it be the motor straining at that exact voltage step?

Oh, that's a great find. I remember that night too. Our whole neighborhood was quiet because everyone was inside watching it. It felt like the whole country just stopped for a couple of hours. I don't think we'll ever see something like that again with how we watch TV now.

Heard that jigs are a total game changer for scroll work.