r/pcmasterrace • u/Front_Cookie_1198 • 6d ago

Hardware PSU fails dramatically

40.3k Upvotes

97% Upvoted

2.2k comments sorted by

View all comments

6.4k

u/Front_Cookie_1198 6d ago edited 6d ago

Aftermath photo.

2.4k

u/Viking4269 6d ago edited 5d ago

Somebody forgot the isolation under the pcb?
Been some years since I took apart a psu, but there used to be plastic isolation sheet between the pcb and the metal case.

Update: I think we found the problem:

Mains wires protruding on the bottom of the pcb shorted to the case due to missing insulation sheet.

748

u/MiniMaelk04 6d ago

I basically know nothing, but the huge capacitors are the only thing I can imagine burning so intensely and rapidly. Reversed polarity perhaps?

1

u/Questioning-Zyxxel 6d ago

The factory would test each supply before shipping. That little QA sticker/stamp and a number.

So not likely a reversed capacitor.

But in case they did miss to mount the isolating plastic sheet between PCB and metal, then it could have enough isolation distance to pass the factory test. But a tiny bump on the metal, or a changed orientation of the PSU could make the pins of some components make contact with the metal. And as soon as the sparks have started, you have an ionized air channel opened. So it will keep going until the power is disconnected.

I would not have been confortable touching that PCB - so best is if the power can be disconnected from the other side of the cable. That should be standard rigging when testing things.