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Question PSU turns off when 24pin is connected

Jun 23, 2021
Hi there,
I have an HP desktop PC which have a weird problem and I want your help. The PSU on its back have a green led which turns on when connected on the mains. When connected on the Mobo with the 24 pin it keeps blinking. When i remove the 24pin the light stays on. I disassembled everything off the Mobo, CPU ram GPU hard drives etc and i kept only the motherboard and the PSU. If I jump the green and black fans starts spinning and checking with a voltmeter i get all readings of 5v and 12v ok. When I connect the 24pin only on the Mobo PSU green light that indicates it's connected to main turns off instantly and trying to restart and keeps blinking on and off giving no voltage to the motherboard. I checked for shorts on positive and ground on PSU on the 24 pin and nothing. Checked on the motherboard's 24 pin still nothing. What could cause this to happen. Is it the PSU or the Mobo. If it's the Mobo which is a short where should I check for shorts? Could it be the super I/O? Thanks in advance.


HP desktop - model/version?

Update your post to include full system hardware specs and OS information.

Include PSU: make, model, wattage, age, condition?

Check the motherboard's User Guide/Manual for the meaning of any diagnostic LED's.

Any beep codes/patterns?


I think out of the two....PSU or motherboard....I pick PSU as more likely the culprit.

I think if the motherboard was drawing enough current to trip a good PSU....there is decent chance you would see evidence of this on the motherboard. I don't think "guaranteed" you would see evidence...but a decent chance.

I think it more likely that the motherboard is drawing its usual current and the PSU is tripping due to a fault.