Hi guys. So recently I bought an NCR System 3200 computer. Seller stated that the power supply was bad (buzzing noise) and would not power on. When I received the computer, I immediately pulled the PSU and put a multi-meter on it. I checked the wires on the mobo connector, but the 5v and 3.3v looked to be in spec. I wasn't able to test the -12v as the PSU finally blew out before I could get to it. Luckily enough someone on E-bay had 3 of these special type PSU in stock (Lite-On PA-4600-2 60W). Finally came in last night, and immediately plugged it into the wall and checked it before attaching it to the motherboard / devices. No pop, no buzzing; Great!

However, when I attached it to the motherboard and floppy drive, and powered it on, there was an immediate buzzing noise emanating from the PSU. Power and floppy drive LED were flickering. Not good! I pulled the motherboard power connector from the board and floppy drive, and powered up again - no buzzing noise. Proceeded to power cycle it a few more times, this time with only a hard drive attached and without. Hard drive would not power up, and the power supply is now buzzing regardless if it attached to the motherboard / device, or not.

I have looked up an down, back and front, and cannot visually find anything that would indicate a short. No magic smoke, no magic odor, broken or fused solder joints, blown resistor packs, or any place that the board could be shorting out on.

Could this be a fluke and the power supply I received is also defective, or is this board somehow shorting / frying the PSU?