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Computer turning on and off repeatedly

Last response: in Systems
a b B Homebuilt system
September 14, 2010 8:51:23 PM


been having trouble with my PC recently, i'll start off with the specs:

Asus P5K-E
OCZ StealthXtreme
Nvidia GTX260

It started a few days ago when i tried to power on the computer it would turn on and off a few times then eventually it would stay on and act as normal until the next day i tried turning it on. Eventually i decided to open up the case and look to find if the motherboard was shorting on the case, i couldnt find any indication. I cleaned the case out of dust etc then tried powering it on. It wouldnt boot at all and just kept cycling on and off until i had to turn it off by the surge protector.

At this stage i knew i couldnt put it off and had to remove everything from the case to investigate any shorting from the case. Eventually after removing all the components i placed the motherboard outside of the case and tried powering on. It still wouldnt power on properly so i imagine this ruled out problems with the motherboard short circuit. I was really out of ideas now.

I should also point out when trying to power on the cpu fan would spin but the PSU fan would NOT even attempt to spin whatsoever.

I read online that taking out the mobo battery/moving jumpers may solve the problem but i didnt have any luck with this. Saying that, i followed the time of 20-30 seconds of having the battery removed as described in the mobo manual however some people have had it removed for 2-3 hours, I may have to try this. I ordered a PSU today which should hopefully come tomorrow (wed), so i can test the PSU then. I'm hoping it fixes it because i'm really clueless as what the problem could be.

If anyone has any ideas i'd appreciate it.
September 14, 2010 9:46:09 PM

Is it overclocked at all? If it is set the bios to optimized settings and see if that helps.
I dont know about the PSU it could be going bad, or the fan never had time to turn on but I dont know. Do you have another one laying around, if so try it.
September 14, 2010 9:46:32 PM

Oh what size PSU
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a b B Homebuilt system
September 14, 2010 9:52:01 PM

size? standard ATX size PSU i guess. If you mean watts? then 600w.

I can't get into BIOS but i've tried resetting the jumpers etc but it didnt make a difference.
September 14, 2010 10:10:00 PM

Do you have another cmos battery? Sometimes when they go the computer wont boot.
a b B Homebuilt system
September 15, 2010 5:18:07 AM

One problem that can cause your symptom is inadequate cpu power, for example, leaving the 4/8-pin connector unplugged. This could also be caused by a failing/failed psu.

There are several ways to clear CMOS - this combines all of them:

Pull plug from wall, turn off PSU switch, remove battery, press "Clear CMOS" button several times if equipped, press case Power Button 10 times, go grab a cup of coffee.

When you come back, CMOS is clear.

September 15, 2010 6:21:02 PM

Just wanted to say that I had the same symptoms as the OP, I would press the power button and the fans would run for like 2 seconds, then shut down, the run for 2 seconds, shutdown, etc. I took off the battery for a couple minuts and it solved my problem. If your computer doesn't power on, make sure your POWER SW pins from the front panel are in the right pins... I know it's stupid but I actually replugged them in the wrong ones and wondered for like 2 hours why my computer wouldn't turn on!