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Home Built Computer Constantly Reboots Itself

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December 11, 2011 7:59:21 PM

I built my computer 2 years ago in September. Two weeks ago it randomly shut down on me and would go into a rebooting loop.


System Specs:

Windows 7 x64
i5-750
Gigabyte GA-P55M-UD2 LGA 1156 Intel P55 Micro ATX Intel Motherboard
HIS Radeon HD 4890 1GB 256-bit GDDR5 PCI Express 2.0 x16
Spinpoint F3 500GB 7200 RPM
Antec Basiq BP500U 500W
G.SKILL Ripjaws Series 4GB (2 x 2GB) 240-Pin DDR3 SDRAM DDR3 1600
Spinpoint F3 1TB 7200 RPM [This was added a year later in October of 2010]


Steps Taken:

1. Test PSU - Done [Clear]

2. Take out one stick of memory at a time- Done [Clear]

3. Take out second hard drive - Done [Clear]

4. Disconnect all external hardware - Done [Clear]

5. Boot from OS CD - Tried [Inconclusive; The computer doesn't stay booted long enough for me to do this. I can't even access BIOS.]

6. Check CPU and CPU temps - Done [Clear]

At this point I'm thinking it's my motherboard that has died on me but I'm not quite sure how to test it and if there is something that I'm not seeing or looking for. :heink:  Also, is the RAM incompatible with my CPU? I checked Intel's site and they recommend DDR3-1066/1333. Never realised this until now.

I would really appreciate any sort of help. Thanks.
a b B Homebuilt system
December 11, 2011 10:09:28 PM

Your RAM sounds fine, yours is overclocked DDR3 1333. Motherboards are difficult to diagnose. PSU's will degrade over time. I think I would try a new 600W PSU before replacing the motherboard, unless you just want to build a new rig.
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December 11, 2011 10:20:43 PM

Exactly how did you test the PSU? Even though components are powered up, and if you used the paper clip technique, that is not a 100% guaranteed test that your PSU is working. A PSU tester would be better, or trying a new PSU entirely.

I'm confused about your step 5. So you tried booting the OS from CD, did you get anything off of that? AKA did you see it loading windows files, THEN suddenly stopped working, or it just would not boot anything from CD at all? And when you mean can't even access BIOS, did you try waiting a good 10-15 minutes before powering it on again, THEN trying to access the BIOS? Because if it shuts off, and then when you try turning it on immediately again and it shuts off quicker, then most likely looking at a power supply issue.
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December 11, 2011 11:33:13 PM

I checked the PSU using my Coolmax LCD PSU tester.

As for step 5, I put in the CD but the computer never gets far enough for it to be recognised. Yes, I did wait for 10-15 minutes after a while but what you described (Because if it shuts off, and then when you try turning it on immediately again and it shuts off quicker, then most likely looking at a power supply issue. ) did in fact happen. Do PSU testers give false results?

I don't have a second PSU to check if that is indeed the issue but I am willing to buy a new one. Do you guys have any suggestions? I've been looking at this one from NewEgg:

http://www.newegg.com/Product/Product.aspx?Item=N82E168...
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a c 122 B Homebuilt system
December 12, 2011 5:07:31 AM

The problem with any of the inexpensive PSU testers is not "false results", but that they present almost no load to the PSU.

If you can borrow a multimeter:
use a DMM to measure the voltages. Measure between the colored wires and either chassis ground or the black wires. Yellow wires should be 12 volts. Red wires: +5 volts, orange wires: +3.3 volts, blue wire : -12 volts, violet wire (standby power supply): 5 volts always on. The green wire should also have 5 volts on it. It should go to 0 volts when you press the case power button, then back to 5 volts when you release the case power switch. Tolerances are +/- 5% except for the -12 volts which is +/- 10%.

The gray wire is really important. It should go from 0 to +5 volts when you turn the PSU on with the case switch. CPU needs this signal to boot.

Do this with the main power plug and CPU power plug in the motherboard. If any of the voltages are out of tolerance, the problem is either PSU or motherboard.
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