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I have this not-so-old computer that's not being used for a year or so.


  • Motherboard: ASUS PN5-E SLI
  • CPU: Intel Core2Duo E4300
  • RAM:2x2GB SuperTalent DDR2-800
  • VGA: Zogis GeForce 7950GT
  • PSU: Vitsuba San-55-S 550w
  • HD: No hardrives yet

When I power on the computer, everything seem to start, but right away the whole system shuts down.

I've removed and changed the RAM sticks, take out the VGA, everything I could think of.

So what could it be causing this? The PSU? The motherboard is dead? The CPU? Any help to isolate the problem will be useful.


PS: Please don't close the question, this could be helpful to anybody having a similar problem, even with different hardware.


  • I've removed the old thermal paste and apply a brand new one.
  • I also cleaned every dust using a high pressure gas dust remover.
  • Checked for bad capacitors, all of them seem ok.
  • Opened the PSU, removed big giant dust balls, cleaned with high pressure dust remover.

Still the same problem, but now it stays powered on for almost 20 seconds maybe. But no POST screen, no beeps at all, nothing.

So I suspect it's a motherboard or PSU failure. Unfortunately I don't have an energy tester to test the PSU...

Don't know what else to try. I don't have another 775-motherboard to test the CPU, RAM and VGA with it.

share|improve this question
What's the history of the problem? Did it just suddenly not turn on one day? Or were hardware changes made and then it didn't turn on? Or was it stored for a long time and then didn't work? My guess would be that CPU cooling is the problem. For example, bad heatsink mounting, bad heatsink fan, or heatsink fan connected to the wrong connector. – David Schwartz Mar 23 '12 at 3:30
How far do you get in the boot process? BIOS splash screen? Or do the fans just come on briefly? – Mark Johnson Mar 23 '12 at 3:32
@DavidSchwartz I stopped using it because I bought a new one. I'll clean the thermal paste and apply a new one to see if it's the temp. – emzero Mar 23 '12 at 4:20
@MarkJohnson No POST screen. The fans (and the whole system) turn off after 1 or 2 seconds. – emzero Mar 23 '12 at 4:21
possible duplicate of Computer won't stay powered up – Ƭᴇcʜιᴇ007 Mar 23 '12 at 4:24
up vote 4 down vote accepted

Off of the top of my head, I'd guess a bad power supply. You could check it with a power supply tester, but sometimes they don't fail unless they are under load.

As EKW is pointing out, you could be looking at some sort of thermal shutdown. I guess I could believe a year in the right conditions dried out whatever thermal compound is installed and left you with a gap. How long does it keep running after you hit the power? You might visually inspect the capacitors on your motherboard to see if maybe you've got a bad capacitor, as suggested, too.

During this year in which it was not used, how was it stored? Was it unplugged? If not, it might have been damaged by a power surge. Temperature? Humidity?

Even with the info you've provided, there's not a lot to go on, and the best you're probably going to get are guesses. Assume everything is faulty, and if possible, swap in known good components where you can get your hands on them. You could also try your components in other systems. Hopefully you've only got one bad component and you'll be able to isolate it via a process of elimination as you prove components good or replace them with known good ones.

I've done this dance many times. Remember to kill the power (at the plug) before taking stuff apart or you might let the magic smoke out. Good Luck!

share|improve this answer
HSF could be dismounted, not properly mounted, or not have the gap closed with thermal grease, as well. May also be bad caps on the board. – EKW Mar 23 '12 at 3:31
@EKW Could be many different things. I put the power supply at the top of the list somewhat arbitrarily. – Mark Johnson Mar 23 '12 at 3:36
PSU is also the easiest/cheapest thing to test. – Journeyman Geek Mar 23 '12 at 4:16
@MarkJohnson It was stored with the case opened. So it could be the thermal paste old and dry. I'll clean and re-apply it tomorrow and will be back to you. Thank. – emzero Mar 23 '12 at 4:31
@MarkJohnson I have updated my answer including what I've tried today. It didn't work. Any new ideas? – emzero Mar 23 '12 at 19:47

I've been seeing this happen all too often at my workplace. There appears to be nothing wrong but it will not boot, and restarts after 10-20 seconds.

  • First, try to take the RAM out completely and power the machine up. If it beeps, then you know the motherboard should (in theory) be OK.

  • At that point, change RAM and/or PSUs.

  • I have seen one other (very odd) occurrence where the problem was actually the onboard NIC. I could unplug the Ethernet cable and it would boot without a problem; when I plugged the ethernet back in (even if Windows was loaded), it would crash. To resolve this, I popped in a PCI NIC and disabled the onboard NIC on the motherboard.

Just a few options for you to try!

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As has been already said... there isn't enough to go on. It could be any of the components attached to the motherboard. Seriously. It could be the video card, one of the sticks of RAM, the processor itself, the power supply... it could even be a capacitor that is damaged (but not to where you can see the issue). As you point out, you do not have the equipment to test all these components, or to even test the motherboard independently with a different processor. This means that you are essentially stuck.

You could test the power supply, RAM, and Video card on another computer.

You could test this motherboard and processor with a different PSU, video card, and different RAM.

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