I've had my Apple //e for a few weeks; the first day I had it, the power supply catastrophically self-destructed. By that I mean one of the uber-fun paper AC filter capacitors blew, leaking out burning icky gook. I had to clean that off of the PCB eventually (or I just thought about it for a while, decided it wouldn't short anything out anytime soon (hopefully), and forgot about it). Yay.
I was in the garage writing some BASIC programs on my //e and heard a hissing noise; I thought for some reason that there was a snake or lizard in the garage, so I turned my back to the computer for a look around, only to turn back to the PC and find smoke coming out of it. Not a great sight. My garage smelled of burnt marshmallows for days. However, luckily, the computer was not damaged, and I wasn't worried because it continued functioning perfectly up to the moment I unplugged it, indicating that the cap's failure did not cause damage to the main motherboard and was not function-hindering.
Thus goes my adventure of replacing the old electrolytic capacitor in the Apple //e power supply, which is quite simple and an intriguing journey into a wonderful product's design.