The only time I did anything silly was when I had an ancient Kaypro CP/M machine. Well, the floppy drives had been playing up for ages and I finally worked out that the power connectors were loose. Took it apart, tightened the connectors properly, put it together again, turned on... and smoke came out I'd plugged one the connectors one pin over by mistake... blew a few chips, including the one that interfaced with the keyboard. Well, you can't get Z80SIO chips any more, so that was the end of that.