Question about ASUS P4S8X Motherboard

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Not powering up

My ASUS motherboard has been running for 4 years. I have not make any recent changes to either hw or bios or settings. The board will no longer come alive. Button works correctly. I the computer was on and when I came back to it about 30min later it was off. The board does have power as the green PWR led is on, but the Red AGP Warn LED is also on. This LED is to indicate to the motherboard that a non 1.5V AGP card is present and the board will not power up. The video card was never touched or changed. Even with the card pulled out, this LED stays on. The power supply is able to power another computer fine. Also, when I measure the 5V rail (the one wire from the supply that is on all the time) it drops down to below 4.7V when plugged into the mother board. I am assuming the all the wire wires and voltages do not turn on because it never receives the power_on signal). When the power supply is powering the other computers, the voltage rails are normal. My computer does not have alot of devices on them, so I don't think the power supply is overloaded. I suspect there is a short on the motherboard butI cannot find any component that gets hot. I disconnected everything except the processor and the voltage still drops to 4.7V. On the rare occasion, I had to turn it on and off to get the voltage to drop that low. (it still did not power up when the voltage read above 5V) I really would like to confirm that its the motherboard. Should the AGP_Warn led stay on even if there is no video card plugged in? Any other sugggestions to look at. I don't want to just to do part $wapping to isolate the problem.

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Re: Not powering up

Sounds like you have done a lot of the footwork yourself and that helps. Have you tried the AGP card in another computer? Do you have an auxiliary fan in your CPU box? Do you normally leave the computer on all the time or shut it off when not in use? Seeing all you did I will assume the MB is clean of dust/dirt. The voltage drop is rather minor but may indicate a short. There normally is a sag when the MB is drawing current. 4.7V should still be sufficient for proper operation of TTL parts. I would suggest checking closely, with a microscope or some other type of magnifier, for a bent pin in the AGP slot. It is possible that it has been bent all along but slowly caused a short due to excessive current draw. Since the MB is 4 years old it might be time for an upgrade anyway. To diagnose further, w/o the aid if a schematic, would be costly and would liekly exceed the cost of buyng a replacement. Good luck.

Posted on Oct 31, 2006

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