I spent the afternoon testing ATX power supplies, found three that failed, two 600watt P4 era PSUs and a nice Cooler master 500watt that failed badly, the CM500 had massive over voltage on the +5v rail. The two 600watts that failed one was making a loud squealing noise that wasn't the fan, pretty sure it was from the coils on the board but the PSU was tripping its OCP after a second or two on the tester, the other wouldn't even power on fully, the fan would twitch but the PSU itself was no bueno.
All three have been sent to the great Ewaste yard in the sky, I don't have the experience or knowledge to fix these PSUs at the component level and they are not worth passing on to others who do. Its a shame about the Cooler Master as it was a nice looking PSU but the +5v was hitting ~8v without tripping OCP. (Its possible the PSU didn't have OCP on the +5v rail)
If I didn't live in rural South Australia I may have offered them up here as a free giveaway to anyone wanting to repair them, but shipping costs are stupid right now so that's the only reason they got wasted.
I did have another I tested its a 600watt P4 Era PSU but it worked fine aside from its +5v being a little high but its delivering 57Amps on that rail and without a load it may have been confusing the tester, it checked out fine with a multimeter and a fan on that rail, might make that PSU my Athlon XP supply, with 57Amps on the +5v rail its for sure the perfect PSU for it, also has the 4pin plug and 33 Amps on +12v too so not a bad little PSU overall.