A few months ago I was rudely awoken in the middle of the night by the “exciting” smell of burning electronics! I got up fairly quickly and wondered what I could have possibly left on. It turns out it was not a project of mine, but (after some smelling around and unplugging of everything within sight,) my PC power supply. 2AM is a great time to catch fire!
As the pictures show there was a small scorch mark on both sides of the PCB. A blackened resistor is the culprit. I believe the root of the problem was bad capacitors possibly shorting out a power rail. The PSU was making some high frequency noise previously, notoriously caused by bad caps.
To get this far into the power supply I had to pull a lot out. It ended up being a good source of some components, but I never planned on repairing the supply. A good capacitor has already come in handy temporarily repairing an old HP 3478A.