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PC power up and shuts down automatically

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January 24, 2013 2:30:30 AM

I switched on the PC but after a few seconds it shut downs by itself. Sometimes I am able to get enough time to get into Bios settings or to the windows boot up screen, but usually dead after that. There are also occasions when the PC shuts down automatically and then attempt to start up again by itself.

I have removed all pc components and leaving just mobo, 1x 2gb ram and hard disk.

When I tried booting the PC without the hdd, going into bios, it still shutdowns automatically after awhile.

Also noticed that sometimes the chasis fan continues to spin and the LED light is lit up after the pc shut downs automatically.

The pc is about 3-4 years old.

Is it the power supply or motherboard that is causing the problem?
January 24, 2013 5:11:01 AM

there is a few reasons that this could be happening. you might have a bad solder joint on the motherboard and once the joint heats up it causes it to become a bad connection and than it cools down and hardens back up. that could be one reason. do you have any spare power supply's laying around that you can start doing some troubleshooting?
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January 24, 2013 5:33:55 AM

What PC? With just CPU/stick RAM does it maintain BIOS long enough to check for high temps? Post your PC model number anyway...
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January 24, 2013 5:43:27 AM

dodger46 said:
What PC? With just CPU/stick RAM does it maintain BIOS long enough to check for high temps? Post your PC model number anyway...


i was thinking over heating too. because he said it randomly starts back up. why is that will it do that when it cools back down. i have never seen that doesn't it usually lock up.
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January 24, 2013 5:50:14 AM

pcgamer719 said:
i was thinking over heating too. because he said it randomly starts back up. why is that will it do that when it cools back down. i have never seen that doesn't it usually lock up.

Best to try to rule everything out bit by bit, overheating can cause strange results, and maybe if he has a decent BIOS it will be possible to check Motherboard voltages, which is why it's useful to know PC model ...
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January 24, 2013 5:52:58 AM

It's a DIY PC, i took out all other parts except for

mobo ASUS P5N73-CM
cpu intel E5200
psu Cooler Master 550W Extreme Power
ram 2GB DDR2 800
hdd 640GB WD Cavier Green

I will try it out later to see if I can check the temps, if I am lucky i may be able to have almost up to 30 seconds in bios and then hangs in bios then shutdown, if not it will just shutdown in seconds after start up. Btw the pc is cold boot start.

Still trying to source for a psu, if i can't get one to test, i considering buying one.
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January 24, 2013 5:57:46 AM

Disconnect the HDD and try again, Cooler master a reliable PSU, and HDDs can cause real problems...
Your Manual here http://www.asus.com/Motherboard/P5N73CM/#support_Downlo...
Go straight to the Power Tab (P60) to check your temp and voltages, esp Rail volts (12, 5, 3.3)
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January 24, 2013 6:04:16 AM

ok you can check your temps on that mobo from your bios but your going to have to be fast. also that mobo is usually very good at handling higher temps. what is your processor because you have a better chance of that starting to throttle in 30 seconds. is the fan on your processor firing up when you start your pc? if you give me your processor i can tell you what temp it throttles at and you can check from your mobo and we can try to rule them two things out before you go buying parts that you might not need.
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January 24, 2013 6:13:26 AM

HI!
There have been 3 or 4 cases that I had similar issues with a couple of rigs I owned within the last 7-8 years. 3 out of 4 I think were caused by faulty PSU. Try to find one and test it ASAP. The problem is that in my case -cause I couldn't borrow one as well- this lead to me buying a cheap one just for some days until I had the original replaced.
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January 24, 2013 6:17:50 AM

When I start up the PC, the processor fan starts firing up, the chasis fan also starts up. I only know that my processor is an intel dual core E5200. I will update the temp and voltage when I get back to test the machine again later.
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January 24, 2013 6:17:54 AM

@mike im in your shoes now i bought a non modular one and now im regretting it every time i look at the nest of wires everywhere i think everyone always does that. its natural everyone wants to drop everything into processor gpu and mobo thats where the performance is lol.
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January 24, 2013 11:31:24 AM

Now the PC can't even boot to bios. I swap to a working PSU, and it is still the same behaviour. PC boots for 1 second, then shut down by itself. Seems like it is the mobo problem.
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January 25, 2013 4:36:31 AM

look at the comment i sent you first about mobo repair that might do the trick i have been doing pc repair for a long time. if you dont see any cracked welds than i am going to have to go with a bad processor. switch back to the old psu see if you can get the bios settings back and remove your battery from the mobo.
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January 25, 2013 5:08:56 AM

yagamiori said:
Now the PC can't even boot to bios. I swap to a working PSU, and it is still the same behaviour. PC boots for 1 second, then shut down by itself. Seems like it is the mobo problem.

Could also be the CPU, you could get a cheap Celeron from Ebay to check.
http://www.ebay.co.uk/sch/i.html?_trksid=p3984.m570.l13...
Cost you less than a new mobo...
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January 25, 2013 2:20:21 PM

I took out the processor and power on, power did not go off, just blank screen on the monitor, fan running, led, power light all remain on. Seems like it's the processor, but I am not sure if the mobo is still working when I am without a spare cpu to test it. May try to get a spare celeron to test it out.

I also manage to test the power supply on another working machine, manage to boot, however i noticed the chasis fan remained running but slowly after i shut down, the chasis fan only stop when i turned off the mains. So I was quite doubtful about the working condition of the psu. Didn't want to risk any machine using that.

So in the end I went to a shop and willingly get conned by the shop owner to get replacement, a Coolermaster 475w, G630 and a Asrock board. The machine is up and running fine. Thanks everyone.
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January 25, 2013 2:23:03 PM

Best answer selected by yagamiori.
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