Question PC powers on for 1/2 sec then powers off

paulfoel

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Jan 29, 2014
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Existing PC that has been working for a while.
Asus Z270H mobo and amber standby light is lit.

Tried powering off completely, removing power, no difference.

PSU and case fans start for about 1/2 sec and then it powers off completely.

Next step - check memory seating?
 
Oct 26, 2020
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This may be a stupid answer/solution, but sometime simple is best...
Just had GPU probs and removed it. Went back to onboard chipset until I repaired GPU and reinstalled it. Had the same prob after reinstallation - every time I pushed the start button on PC the light would come on for a sec then go off. Fans on board would spin for that same sec then go off. PC has worked fine and always started for the last 11 yrs.
I removed the front cover of the PC where the start button is mounted and even though I regularly blow out the dust from the case, there was a big plug of dust and gunk that wouldn't let the start button make full contact. Blowing didn't get it out, I had to dig out that plug by hand. I put the button assembly and cover back and pushed the button and it worked again just like new.
I don't pretend to know what I'm doing but this worked for me, hopefully you too. Good Luck
 

paulfoel

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Jan 29, 2014
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hmmm ok worth a look I guess.....Interesting.
Yeh taken EVERYTHING out now. All memory, connectors, graphics card and its the same.

I had an overheat on my other PC and it was different. Stayed on for like 5 seconds.

This is different. Almost like you said. as if it starts to power then the button doesnt allow it. I guess one way would be to short the connector somehow too.
 

paulfoel

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Jan 29, 2014
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Its my sons PC too. At 17 hes not the most careful person in the world. Hes managed to trash many mice, keyboard etc. I wonder if hes done something to the power button hmmmm....
 
Oct 26, 2020
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When you push the start button - just hold it in for about a minute - and see if the PC stays on and starts booting like normal. Then when you let it go if it goes right off then pretty obvious it's the button switch. Mine wouldn't seat far enough so the button never 'locked' in the on position until I removed the blockage (just a couple mm's of gunk can keep it from 'locking in').
I sincerely hope that's all your problem might be. Once again, good luck!
 
Oct 26, 2020
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I clean out the inside of my PC every 2 - 3 months with canned air. Been doing this for YEARS.
I'm now thinking that those strong bursts of compressed air is what shoved all that dust/gunk into the front cover (which is not very well vented) and somehow wedged in the button mechanism. I think now, at least yearly, I'll remove the front cover and dust that closed off area as well. Who knew??
 

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