computer powers off after being on for 3-10 seconds

[sotorious]

Ok well we had some lighting today but power did not go off, maybe made some of the things flicker for half a second.

After PC shut down went to go turn it back on, would boot for a few seconds but then turn off, never got the beep from the mobo or anything

Things i tired.

Different power supply (same thing)
Removed CMOS and put back in (same thing)
left all but 1 ram in (same thing)

I am thinking its the mobo but i want to be 100 % sure before i go out an buy a used one, as for some reason 1366 mobos are expensive...

Can it be the processor @ all?

 

[TVeblen]

No, processors are tough SOB's. Any brand, any model - other that anecdotes and computer campfire stories it is very rare to actually see a processor die. You have to work hard to kill them!

I would do the standard no-boot diagnostic to determine the cause. Just be sure about the power supply, because that is the component most likely to be affected by a surge caused by any lightning.
(Don't forget to suspect the surge protector power strip! Bypass it, or use another to test.)

The diagnostic:
Basic diagnostic procedure is to uninstall the entire build and start over. Some people do this out of the case by placing the motherboard on an anti-static surface. This eliminates the possibility that there is a short circuit between the motherboard and the case through the connection posts (stand-offs). A standoff in the wrong location or a sloppy job will cause a short.

The Test (power off, power cord unplugged):

• Disconnect everything externally connected except the mouse and keyboard (printers, USB devices, etc). If you are not using a wired mouse and keyboard see if you can borrow one. The wireless device is just another component you have to deal with.
• Disconnect the power and data cables from all the drives inside the computer (Hard drives, DVD/CD drives, etc).
• Remove all the cards installed in the expansion slots (PCI/PCI-e) including the video card. (Be careful handling them and place them on a non conductive surface while testing).
• Remove all the RAM sticks (same rules as above).

Now connect the power cord and turn the PC on.

• The motherboard should start beeping. You should get a beep code that tells you there is no memory. This is good, it means the processor is functioning and the motherboard is good so far.
• Now add one stick of memory in Slot A1 and power on. More beeping: "no video card" beep code. This is good.
• Then add the video card and connect it to the monitor. You should get no beeping and you should see the BIOS start screens, ending with the message that there is no boot device.
• If you get no video then switch the one memory stick installed for another one and test.
• If you do get video then start adding components back, one at a time, until the system fails to boot. The last component you added is then the problem component.

If the problem you describe occurs with nothing but Power Supply, Motherboard, and Processor then you know it is one of those 3.
If you are certain about the power and power supply, and we can reasonably rule out the processor, then it must be the motherboard.

Hope that helps. Sorry for your loss.

 

[PaulyStones]

Have you considered changing the CMOS battery? Maybe it burned out...once you change that...you might be able to tell if the BIOS is configured correctly for the monitor or disc drive...

good luck

 

[sotorious]

Power Supply I am sure, because i took it out of a pc that i had powered up that i shut down to install the new psu, and re installed it back into the pc. I have not done the dis assembly, i can just use any old cmos battery?

Also shouldnt the mobo beep anyway upon start up?

 

[TVeblen]

Yes. The single beep is the POST (Power On Self Test). It indicates that the motherboard is receiving power, the logic circuits check out, and the BIOS chip has been found and recognized.

But a shorted motherboard or burnt out component connected to the motherboard will disrupt that process and then: no beep.

 

[sotorious]

Ok will run those tests before i go buy another mobo.