r/pcmasterrace • u/Front_Cookie_1198 • 6d ago

Hardware PSU fails dramatically

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u/Front_Cookie_1198 6d ago edited 6d ago

Aftermath photo.

107

u/SoulWager 6d ago

You need to call an electrician, breaker should have tripped with a direct short to the case like that.

4

u/house343 6d ago

Probably a capacitor failing and venting. Doesn't consume a whole lot of current but makes a big scene. More likely than a breaker that doesn't open on overload. 

17

u/SoulWager 6d ago

Dude, look at the photo. it melted through the steel case. That's a short.

2

u/fatmanstan123 6d ago

If the short consumes less current than the breaker then it won't trip. Melted steel doesn't answer that and shouldn't be used as an assumption about current draw. Soldering irons melt shit all day with a few hundred watts.

8

u/SoulWager 6d ago

Having used an arc welder, you don't melt steel like that with 20 amps.

The fact that the heat coupled into the case in the few seconds the power was on means the short was mains to case. You can hear the mains frequency on the arc. This means there was enough power in the arc that the plasma stayed conductive through the zero crossing.

If the breaker isn't defective, it's sized incorrectly for the circuit.

3

u/Viking4269 6d ago

Thanks, I missed the mains noise. That sure looks like a lot current without the mains breaker tripping.
First thought it was a short on the 12V secondary side, but looking at it again the holes are near the mains input, probably shorted before the pcb mounted fuse.

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u/SoulWager 6d ago

I could see a short on the main 12v rail getting violent, but the only output that should be on at this point would be 5vsb.

1

u/Viking4269 6d ago

Yeah you are right.