Has anyone had experience with a shorted power supply destroying a MOBO? I removed a PSU from a dead computer and installed it to a known good computer. Now that computer sounds like it's running as soon as I plug the power cord into it (without pressing the power button) but otherwise is dead- no video or anything.
I've never run across this problem before and I don't recall reading about anyone else ever having it. Online searches haven't helped much either- apparently it's a very rare problem. I tested the original computer with a known good PSU and when it wouldn't start with that, I mistakenly assumed that the MOBO was the whole problem. Since we are short on spare PSUs and cash around here, I wanted to save the original PSU for other systems and wanted to make sure it worked before I saved it.
Using 20/20 hindsight, I did a multitester pinout test and one of the +5 volt pins read about 8 volts. That is several volts above tolerance and is probably what ruined the boards. I'm going to have to be more careful in the future. Fortunately, the systems I ruined are older systems that already had problems so it's not a huge loss but I would've liked to be able to fix them. Now that doesn't look like a feasible option.
Yes, you are right. Also, A better name for the subject of this topic would've been: "Bad PSU RUINS motherboard" since it's not certain whether the PSU was actually shorted or whether its overvoltage caused a 'short' or an 'open' in the boards. Had I used a multitester before I posted, I would've given a more accurate subject line. Also, had I searched on line with the updated subject line (instead of using the search term 'shorts') I would've found this forum posting: