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PC shuts off after starting

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December 25, 2010 7:20:42 PM

I'm working on a friend's PC. It's a custom built machine, about 3 years old.

This is the mobo, XFX nForce 750a SLI

Basically, the PC shuts off after trying to boot from the hard drive or CD or DVD.

I swipped the PSU, hard drive (IDE & SATA), DVD/CD drives (SATA & IDE), still during booting the PC turns off.

The board looks clean, no leaks, the cables are all connected. I removed the video card and connected the LCD to the board's DVI port, nothing.

Memtest86 shows that the ram is OK.

Tried loading Win 7 and XP by doing a clean install, 7 stops and XP continues, but the PC shuts off about halfway thru the installation.

Tried Ubuntu Live CD, once the Ubuntu screen shows up the PC shuts off. At that moment I can feel the mobo under the processor is really hot despite the PC has not been running today at all, only the Ubuntu Live CD is the first thing I ran today.

When I access the BIOS everything seems fine, last night I left the PC in BIOS for 3 hours and it stayed ON. I reset all the BIOS setting to FAIL SAFE, still PC shuts off.

HELP!!!

Is the mobo going bad or the processor?

More about : shuts starting

December 25, 2010 7:54:47 PM

tom3k07 said:
I'm working on a friend's PC. It's a custom built machine, about 3 years old.

This is the mobo, XFX nForce 750a SLI

Basically, the PC shuts off after trying to boot from the hard drive or CD or DVD.

I swipped the PSU, hard drive (IDE & SATA), DVD/CD drives (SATA & IDE), still during booting the PC turns off.

The board looks clean, no leaks, the cables are all connected. I removed the video card and connected the LCD to the board's DVI port, nothing.

Memtest86 shows that the ram is OK.

Tried loading Win 7 and XP by doing a clean install, 7 stops and XP continues, but the PC shuts off about halfway thru the installation.

Tried Ubuntu Live CD, once the Ubuntu screen shows up the PC shuts off. At that moment I can feel the mobo under the processor is really hot despite the PC has not been running today at all, only the Ubuntu Live CD is the first thing I ran today.

When I access the BIOS everything seems fine, last night I left the PC in BIOS for 3 hours and it stayed ON. I reset all the BIOS setting to FAIL SAFE, still PC shuts off.

HELP!!!

Is the mobo going bad or the processor?


If you have access to a motherboard that is compatible with that processor i would recommend trying that to rule out the mobo. I experienced the same issue as you with a socket 462 mobo. there were no signs of damage to the mobo although replacing the mobo worked in that situation. sometimes there is a short that is not visible within the motherboard that could be causing the problems. other times it might be the case causing the shorts.
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December 25, 2010 7:55:00 PM

Try reseating the cpu heatsink, might be getting too hot and shutting itself down. And make sure all fans are spinnning and fins are free of dust.
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December 25, 2010 8:00:28 PM

Already reseated the heatsink. All fans are OK. I have no access to a compatible mobo.
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December 26, 2010 4:09:11 AM

At this point, the CPU temp reaches 48 degrees C while in the BIOS, and then the PC turns off by itself. I will pick-up some thermal compound and reseat the heatsink with the compound in place. Will keep you posted.
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December 26, 2010 4:34:57 AM

Have you checked for bad caps?
ive seen more then one mobo do that due to bad caps.

emachines are notorious for it.
check all the tops for any bubbling up, or if they are tilted, and not flush with the mobo.
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December 26, 2010 4:47:39 AM

All caps look normal.
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December 26, 2010 4:56:07 AM

:( 

only way to really tell would be to use a capacitance meter
but thats not a tool most people have :lol: 

when my mobo failed, it did the same thing you are explaining, even getting hot.
come to find out it was bad caps near the cpu, somehting about voltage regulation.

maybe try and see what the voltages are in the bios ?
also, poor quality PSU's will do wierd things to motherboards.

good luck with it!
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December 26, 2010 5:16:19 AM

I already replaced the PSU with a CoolMaster. At this point it is much easier to just trash the MOBO & CPU and pick-up something new.
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December 26, 2010 6:45:51 PM

OK, thermal compound applied. Now, the DVD drive doesn't work, and I do not see anything on the screen. It's all BLANK. Tried the DVI and VGA ports. Says no signal coming from PC.
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December 27, 2010 1:05:47 AM

I scrapped the whole project, replaced the mobo & cpu.
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November 21, 2012 8:00:12 PM

I had the same problem. I unplugged the comp and left it for about 1 hour. This apparently resets the CPU. Worked for me. I was about to throw the computer in the bin.
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