I remeber when my dad retired from building computers in the late nineties. We were installing a new part (I think it was a Voodoo card) (well, he was, I was in the "watch and learn" phase), he connected everything back to the PSU, turned the power on and the magic smoke escaped.
That was the moment when he hung up his hat and told me I was in charge of the home PC now.
He found the problem by the following morning, actually: he plugged the FDD molex connector back in with too much force at an angle and shorted two pins. But he would never look inside the case again.
It was really easy to fry/break stuff with a lot of the big old parallel connectors especially if you were fiddling around under a desk. I switched to Macs about 15 years ago and, other than repurposing an old Windows homebuild for Linux at one point (for reasons that became largely irrelevant), I pretty much got away from doing that sort of thing.
That was the moment when he hung up his hat and told me I was in charge of the home PC now.
He found the problem by the following morning, actually: he plugged the FDD molex connector back in with too much force at an angle and shorted two pins. But he would never look inside the case again.