PC turning on and off, onboard LED is flashing

Hello guys!

I decided to make a post here because there is no where else to go I'm afraid. Yesterday I was on my PC and everything was working fine, no problems whatsoever.

This morning I turned on my PC, and nothing happened for 5 seconds. Then the PC booted normally for about 20 seconds, and then PC turned itself off. I was like huh weird, but had to go to toilet so did that first. When I came back, I found my computer booting again, and after a few seconds it turned itself off again. Really weird!

I turned off my PSU with the switch, and opened my computer-case and did a quick check on the wiring. Everything seemed alright. Turned switch on again, pressed power button and same thing happened (computer booted after a short delay --> after 30 seconds it turned off again). So I started measuring:

1) Power Button pressed; 5 seconds later;
2) Computer booted; 30 seconds later;
3) Computer turned itself off; 60 seconds later;
4) Computer booted; 30 seconds later;
5) Computer turned itself off; 60 seconds later,
6) Computer booted... etc....

It's not exactly 30 or 60 seconds, give or take a few seconds, but there was a pattern.

After being all confused I guessed my PSU broke down. It was 5-6 years old after all. Most parts of my PC have been replaced with better stuff during time, except my PSU and DVD player. I wanted to replace this PSU already some time ago, so I had bought a new one 2 months ago, but never found the time to replace it anyway. So now I did, removed old one, placed the new one.

Now it doesnt even boot. At all. Only thing happening is my onboard LED blinking.

Motherboard manual says it either has to be turned on, or off. So thats worrying.

I don't know what to do about this problem, and really need my PC working again, im working on my thesis lol.

Here is some extra information:

Motherboard: Asus m4a77td-pro
PSU: Corsair CX600 (ATX 600 watt)
CPU: AMD Phenom II, X4 955 Black Edition
GFX: Ati Radeon HD 5850 Black Edition
Memory: D3 4GB 1333-999 DHX K2 Corsair.

p.s. After some googling here are some ideas, but I have no clue of how to check if im correct:
1) The motherboard battery is kaput?
2) The PCcase power wire that leads to motherboard (the 2 pin thingybob) is kaput?
3) I don't believe the CPU is overheating, everything is mounted very solid, all fans and other computer parts are clean (not much dust and crap on it) etc...
4 answers Last reply
More about turning onboard flashing
  1. Quick update:

    After 30 minutes or so (was googling on laptop) the LED was no longer blinking on and off, it just stayed ON. I didn't change anything by the way.

    Pressing reset or power button still does nothing. PC wont boot.
  2. Try removing the CMOS battery, waiting 5 minutes, then putting it back in and trying to boot.

    Oh, and I assume you probably upgraded the GPU at some point? Beware that PSU upgrades are often needed for that, if you didn't, you were overworking the CPU and that might have killed it faster.
  3. I will try removing and replacing the CMOS later this day. Thanks for the tip!

    And yes, I had a 480 watt PSU before (with a previous GFX). I was using the same 480 Watt PSU with my new GFX (the Ati HD5850 Black Edition) for about 4 months, with no problems whatsoever. Because I was thinking about some more upgrades for the future, I already bought the 600 watt corsair one, because it was one sale. So I had it lying around brand spanking new. As I mentioned in first post, I installed it right after the problems started because I thought the problem would be the 480 WATT PSU being kaputt.

    I can't really believe the 600 WATT PSU being the problem as its brandnew. So it has to be the motherboard, or maybe the CMOS (will figure that out later).

    Thanks for the reply btw :)
  4. I just replaced the CMOS battery by a brand new one. Nothing changed. So its either the motherboard or the power button from my case being broke. Im gunna try and find out if there is a way to turn on my computer without using the power button from my computercase. Any suggestions? I read somewhere that using a screwdriver in between the 2 pins on the motherboard should work, but somehow I got the idea I might fry my motherboard for sure that way, or myself for that matter ;-)
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