Friend's computer power on issue

[MxPhenom 216]

I went over to my neighbors to work on his moms comptuer because Norton was messing up something or other. So i also looked at his old one that he claims Staples blew his motherboard up. he says it powers on then instantly powers off i guess. Im thinking its more towards a PSU issue. Since its a LGA775 system with a micro atx board i think it would be easier to just replace the PSU if at all possible, since LGA775 boards are hard to find now for a decent price. Does this sound like a PSU issue. it has a generic Cooler Master PSU.

[caleb]

Yes it PSU related 99%. I had a p35/s775 board that looped in that powerup/poweroff and it was a faulty PSU. It was strange as it sometimes worked flawlessly.

[sneekypeet]

either PSU or a short. I would pull it and look it over well. If the board looks good, go ahead and try it out on the table to eliminate any possible case shorting issues. I mean in the most simple answer, maybe the power switch is broken

[de.das.dude]

take the psu out

from the 24pin jack of the PSU, short the green wire and any black wire with a paper clip.

connect PSU to the mains. it should power up and stay powered on as long as the green and black are shorted. no there isnt any risk of getting electricuted if you touch the green wire.

if it doesnt stay powered on, there is probably some short in your SYSTEM. i would check the fans first, or the lights, if there are any.

[caleb]

Originally Posted by de.das.dude

connect PSU to the mains. it should power up and stay powered on as long as the green and black are shorted. no there isnt any risk of getting electricuted if you touch the green wire.

It won't stay powered up it needs PWROK/5v signal to stay UP.

[assaulter_99]

Originally Posted by caleb

It won't stay powered up it needs PWROK/5v signal to stay UP.

Not playing the devil's advocate here, but if he shorts the green and the black wires (left in the pic), the PSU should stay on if its in good health. I use that trick myself to power 12v chargers and tons of other stuff.

[caleb]

http://www.techpowerup.com/forums/showthread.php?t=25

Perhaps behavior varies between PSU's.
EDIT: Hmm would be good if somebody clarifies this as I'm not 100%. But regarding the original problem when I tried to start the PSU without MB it turned itself off after a moment.

[assaulter_99]

Originally Posted by caleb

EDIT: Hmm would be good if somebody clarifies this as I'm not 100%. But regarding the original problem when I tried to start the PSU without MB it turned itself off after a moment.

Well in my experience, it should work and stay on as long as you've shorted the green and black wires. Chances are that the psu you stated was faulty indeed. Faulty psu's I've encountered usually just power up then die in a fraction of a second. (assuming its from a cold start) But regarding your question, the trick to power it on/off without the mobo works. (judging by all that I've used till now)

[de.das.dude]

Originally Posted by caleb

http://www.techpowerup.com/forums/showthread.php?t=25

Perhaps behavior varies between PSU's.
EDIT: Hmm would be good if somebody clarifies this as I'm not 100%. But regarding the original problem when I tried to start the PSU without MB it turned itself off after a moment.

connect something to load it. like a fan etc.

[sneekypeet]

Originally Posted by de.das.dude

connect something to load it. like a fan etc.

This, there are some PSU's with load sensing, and if they dont "feel" a load, they will shut down.

[_Zod_]

Originally Posted by sneekypeet

either PSU or a short. I would pull it and look it over well. If the board looks good, go ahead and try it out on the table to eliminate any possible case shorting issues. I mean in the most simple answer, maybe the power switch is broken

Bolded part. I had this problem and it is also the first thing to check because it is the easiest and cheapest. Just swap the reset switch for the power switch to test.

[dajjhman]

Originally Posted by assaulter_99

Well in my experience, it should work and stay on as long as you've shorted the green and black wires. Chances are that the psu you stated was faulty indeed. Faulty psu's I've encountered usually just power up then die in a fraction of a second. (assuming its from a cold start) But regarding your question, the trick to power it on/off without the mobo works. (judging by all that I've used till now)

This is what I would do, and it's is supposed to work on every modern PSU AFAIK (maybe not the specialty ones though like picoPSUs)

even some manufacturers supply little jumper wires for standard PSUs so you can test the hardware in the case with power without possibly damaging the system if it doesn't work right (ex watercooling systems can be powered this way without running the Motherboard, so if your cooling suddenly failed you won't damage whatever it was meant to cool).

however, it probably does need a load and I'm sure it wouldn't like floating without one if it has problems

-Jimmy