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Homebuilt randomly shuts down

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September 8, 2009 4:15:58 PM

Hey guys,

I've recently been having an issue with my homebuilt system. A few weeks ago my PC began to shut down randomly and wouldn't boot up for some time. Hitting the power button would get it to blink on but fail to hit POST. I decided to Re-apply thermal paste (Arctic Silver) and it stopped th shut downs. Once again though it has begun again (few weeks later). It wont stay on for more than 30 minutes.

I use CoreTemp and Speedfan to monitor temps. They both never show my CPU over 30c (ide at 25c) and my other temps never go abve 40C. I'm kinda lost. Could it be a PSU Issue?

Here's my specs...

Dark Knight Heatsink
AMD Phenom 2 AM3 720 BE CPU
GIGABYTE MOBO (forget model, its a AM2+/AM3 board)
2 x 2GB OCZ memory
750w Corsair PSU
NZXT Tempest case
September 8, 2009 6:13:47 PM

Check your PSU. If it won't even get to post, then your PSU is giving up the ghost. Eventually, it will give its last gasp and all that magic smoke that makes your computer run will escape.
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September 8, 2009 6:24:47 PM

How does one check the PSU...anything aside from taking it out and putting another one in? Some sort of monitor or... anything, lol.
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September 8, 2009 6:33:49 PM

If you can get into the bios screen and look at your voltages. If you have a bad PSU they will be all over the place. At least they were on my psu nothing was stable. It fooled me too thinking the cpu was overheating. I even bought an Asus star ice cooler. It took two months of playing around. Finally decided to get a new psu and checked the voltages in bios and were very stable. Spend the money on a good PSU I'll never skimp again on that component

Deak
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September 8, 2009 6:45:15 PM

If you can, most any PC shop of reputable nature will be able to hook you PSU up and check the voltages for a reasonable fee. You can also get a cheapo PSU tester that determines whether or not the PSU can even turn on and then use a multimeter to test each rail. Write down the voltages and then compare them to the expected voltage on your PSU's label. This is what I do when I have to question the viability of a PSU.

Even good PSUs go bad. The difference is that the manufacturer is willing to honor their warranty in most cases with an expensive PSU. But, yes, a well-manufactured PSU can make a night-and-day difference between a good build and a nightmare.
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September 8, 2009 11:45:20 PM

I thought the Corsair 750w was a good PSU?

One other question. Is it best to keep the back power switch on or off on the PSU when it is not running?
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a b B Homebuilt system
September 9, 2009 12:56:23 AM

The Corsair is a good psu, but they all fail. Corsairs later and less often.

Don't bother trying to test your psu. There are *many* failure modes for a psu. There is no cheaper, surer psu testing device than a second psu lol. A PC shop can swap a known working one in and if it works, problem solved.

If you can't borrow a psu, contact Corsair, describe the problem, and get an RMA.

Leaving the power swicth on keeps a charge on your CMOS battery which maintains the clock and your BIOS settings. Removal of power for a long time will drain an older batteryand that will make the next boot up a bit problematic.

If you left the power switch on for a year and never used the PC at all, the cost would be roughly $6.57 at $0.10 per Kwh.

Its up to you.
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September 9, 2009 1:47:35 AM

Hello..

May i interject?
Which Graphics card are you using?
I had an identical problem and systematically replaced everything until i finally found out that my gigabyte radeon 4850 was to blame.

if you have a gigabyte ati card, please try a different card and run your usual tests.

one hint is that CRUCIAL Memory's "upgrade advisory scanning tool" was able to crash my computer, now, since i replaced the graphics card, it does not crash my computer anymore.

Good Luck!
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September 9, 2009 3:10:56 AM

When it shuts down, does it try to restart or does it just shut down.

Get the CPUID HWMonitor to check other system temperatures and voltages in Windows (only pay attention to the main voltages as often the others are hooked up wrong or not at all). Post the results of that.

Try running Prime95 (whole system stress) and memtest (memory stress)to see if either of those are the culprit.

Back switch is pretty trivial (notice Dells don't even have one). I turn mine off when it will be off for long periods just so it isn't "idling" there, but really it doesn't have any major benefits or negatives (besides the possiblilty of BIOS battery failing, which I did have happen in one after 5 years).
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