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My Asus P5K Pro won't boot.

  • When I connect the power
    • Powerled on mainboard lights up normally. (doesn't flash, just turns on)
  • When I press the power button;
    • fans spin up
    • powerleds on the front do NOT light up (normally they would)
    • no beeps
    • no screen output

I have managed to boot up a few times after taking out mainboard battery and clearing CMOS RAM. It looked like each time when I changed a random settings in the BIOS (like boot order, or time) I would get the same problem again.

But now I can't get it to boot up, even after clearing CMOS RAM.

I have tried to replace the mainboard battery with a new one, did not help.

Has anyone experienced this before? Any ideas are greatly appreciated!

UPDATE: I don't feel it has anything to do with the power supply. Disconnecting HDD, DVD, USB etc. did not change anything. Also, after clearing CMOS RAM, I have been able to work on this computer for a few days with all devices attached.

UPDATE: I have also tried to remove graphics card and memory, still no beeps.

UPDATE: FIXED: Swapping out the PSU seemed to do the trick, allthough seeing the circumstances this didn't seem likely. After swapping back to the old one, PC didn't work again.

Let's see if it holds up.

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You said lights aren't coming on - did you check your connections and make sure all cables are connected? –  Simon Sheehan Aug 6 '11 at 8:03
    
Yes I checked, during the few times the PC did start up, all lights came on like they should. –  Maurice Aug 6 '11 at 8:18
    
It does always seem weird when you have a PSU failure where the PSU can get the fans running, but that the PC still doesn't boot. Not sure what the electrical cause behind that is, but its a fairly common failure scenario –  Kris C Aug 6 '11 at 11:14

2 Answers 2

up vote 3 down vote accepted
  1. Easiest way to solve this problem – get a new PC.
  2. Not-so-easy way to solve this problem – upgrade CPU, motherboard, PSU, RAM
  3. Hard way: isolate which part is causing the problem, then replace it

    • test PSU
    • check CPU
    • swap RAM
    • test motherboard
share|improve this answer
    
PSU seemed to do the trick, thanks –  Maurice Aug 6 '11 at 10:16

If your computer does not produce any beeps while attempting to boot with no memory or graphics card (assuming it doesn't have built-in video), the motherboard needs to be replaced.

A large majority of motherboards will produce a string of beeps alerting the user to an issue if the system is powered on without RAM. Hence, if your computer makes no beeps, there are bigger issues - ergo replace motherboard.

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Sounds fair, though if the mainboard is broken, how come it did start up a few times in between? I'd expect it to not work at all. –  Maurice Aug 6 '11 at 8:20
    
A couple times out of a 100 is still broken, there are a million things that cause intermittent issues - such as failing capacitors, failing IC's, the works. :) –  DavidChenware Aug 6 '11 at 8:25
    
+1 when I've had these symptoms its either been power supply (relatively cheap to swap a new one in to prove) or the motherboard. I notice you haven't tried swapping power supply yet ("I don't feel it has anything to do with the power supply"). Worth trying though - I've been surprised a few times when I thought it wasn't the PSU, and then swapping in a new one fixed it... –  Kris C Aug 6 '11 at 8:35
    
I just took it to the local store to test if another PSU would do the trick. And it did. Swapping back to the old one and it stopped working again.I now took it home, installed it properly and everything seems to be working smoothly. Considering the circumstances I still find this weird. Now let's see if it holds up. –  Maurice Aug 6 '11 at 10:10
    
Thanks for thinking along guys! –  Maurice Aug 6 '11 at 10:16

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