I built a benchtop power supply out of a computer PSU back in 2008. It decided to finally bite the dust. The power supply still worked, but the circuitry that powered the fan stopped working. I could have just hooked the fan up to the 12v line, but if it does not detect a fan then it limits the output current. So, instead of drilling holes in a new case, I just took the board out of another PSU of the same model and put it in.
Lemme tell you, that was not fun at all. I had to take out the banana plugs, desolder the power plug wires, take the board out, take one from another PSU, put the new one in, and resolder the wires in. That wouldn't have been so bad, except when I went to put the last banana plug in, it wouldn't fit. Turns out that there were a couple capacitors that were about a quarter-inch taller on the replacement board than there were in the old one. So I took all the banana jacks out, too the board back out, desoldered the caps from the old board, put them on the new one, and put it all back.
Then everything finally fit. I put connectors on the wires and hooked them all up, and everything works fine now. I hope I can squeeze a few more years out of it, because the PSU is from 2000 and probably already has plenty of hours on it.
The resistor is 10Ω and 10 watts, and is there to draw 500mA. Switching power supplies will burn out if they don't have a load. And the connector on the far right is the one that wouldn't fit. The caps I had to replace are right underneath it.
The switch on the left is the power, and the one on the right switches the fan off. I only use that when I'm trying to see how loud a different fan is.