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Computer Shuts Off Over and Over

Last response: in Systems
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September 1, 2010 2:25:49 AM

A few months ago I built the following computer:

AMD Phenom II X4 955 Black Edition Deneb 3.2GHz
http://www.newegg.com/Product/Product.aspx?Item=N82E168...

GIGABYTE GA-MA785GMT-UD2H
http://www.newegg.com/Product/Product.aspx?Item=N82E168...

MSI R5750-MD1G Radeon HD 5750 1GB
http://www.newegg.com/Product/Product.aspx?Item=N82E168...

SAMSUNG Spinpoint F3 HD502HJ 500GB 7200 RPM SATA
http://www.newegg.com/Product/Product.aspx?Item=N82E168...

OCZ Gold 4GB (2 x 2GB) 240-Pin DDR3 SDRAM DDR3 1600
http://www.newegg.com/Product/Product.aspx?Item=N82E168...

Antec EarthWatts Green EA-430D Green 430W
http://www.newegg.com/Product/Product.aspx?Item=N82E168...


Right away I started having problems when the computer was under stress. After a few hours of playing video games my computer would turn off as if someone pulled the plug. To get it to start up again I would have to unplug the computer for a while. If I didn't wait a while, turning it back on would just result in the PC shutting off again almost immediately. The length of time the computer would run got less and less.

Right now, the computer just won't boot up. It shuts off about a second after being turned on. All fans seem to work. A weird trick I can do is press power, then as soon as I hear the fans shut off again, press power a second time. For a while this was allowing me to boot my pc, now I just see the memory count and the computer shuts itself off again.

Here are things I've tried:

1) I bought a new power supply. No effect.
2) I tried running each stick of RAM individually, nothing.
3) I switched out the heatsink to an old AM2 and it actually seemed to work a little better. For a while...Now it's shitty again.
4) I ordered a new quality heatsink yesterday.

What should I do? Think it's the mobo? Pretty frustrating.

More about : computer shuts

a b B Homebuilt system
September 1, 2010 3:15:37 AM

If it was the motherboard it should behave the same way each time you try to boot it up, if it gets farther on a cold boot that a boot where it has been turned off recently then i suspect overheating, if your CPU was overheating and causing your system to shut off, when you boot it up immediately the CPU is still very hot, unplugging it for a while wouldnt have changed anything except giving it longer to cool off.

Check your heatsink and make sure its on nice and tight.
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a c 122 B Homebuilt system
September 2, 2010 8:11:49 AM

Because of the design of the heatsinks, AMD CPU's do not have the same potential for cooling problems that Intel chips do. But, yes. Check the simple stuff first. If that is the problem, great. you are done.

If not ...

I think I sounds like a power problem. What kind of PSU was the replacement?

Work through our standard checklist and troubleshooting thread:
http://www.tomshardware.com/forum/261145-31-read-postin...
I mean work through, not just read over it.

Breadboard - that will help isolate any kind of case problem you might have.
http://www.tomshardware.com/forum/262730-31-breadboardi...

Breadboard with just motherboard, CPU & HSF, case speaker, and PSU. You do have a case speaker installed, right? If not, you really, really need one. If your case or motherboard didn't come with a system speaker, you can buy one here:
http://www.cwc-group.com/casp.html

You can turn on the PC by momentarily shorting the two pins that the case power switch goes to.

You should hear a series of long, single beeps indicating memory problems.
Silence indicates a problem with (in most likely order) the PSU, motherboard, or
CPU. Remember, at this time, you do not have a graphics card installed so the load on your PSU will be reduced.

If no beeps:
At this point, you can sort of check the PSU. Try to borrow a known good PSU. If you cannot do that, 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: 5 volts always on. 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.

You can turn on the PSU by completely disconnecting the PSU and using a paperclip or jumper wire to short the green wire to one of the neighboring black wires.
http://www.youtube.com/watch?v=5FWXgQSokF4&feature=yout...

This checks the PSU under no load conditions, so it is not completely reliable. But if
it can not pass this, it is dead. Then repeat the checks with the PSU plugged into the computer to put a load on the PSU.

I'd try this with both PSU's.

If the system beeps:
If it looks like the PSU is good, install a memory stick. Boot. Beep pattern should
change to one long and several short beeps indicating a missing graphics card. Silence or long single beeps indicate a problem with the memory.

Insert the video card and connect any necessary PCIe power connectors. Boot. At this point, the system should POST successfully (a single short beep). Notice that you do not need keyboard, mouse, monitor, or drives to successfully POST.

Now start connecting the rest of the devices starting with the monitor, then keyboard and mouse, then the rest of the devices, testing after each step. It's possible that you can pass the POST with a defective video card. The POST routines can only check the video interface. It cannot check the internal parts of the video card.
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