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System will not start up. Cpu fan spins once, then nothing.

My system will not start up. When I press the power switch, the CPU fan spins once and then nothing happens. After this, the system is completely unresponsive unless I turn the power supply off and back on again, then I can spin the CPU fan once more.

I have verified that I have a good power supply. I have removed all peripherals from my motherboard and only connected the 20-pin power and the 4-pin power to the motherboard. So there is only the power supply, motherboard, cpu, and the ram, nothing else. In this configuration, the "spin once" behavior occurs.

If I remove the 4-pin, the cpu fan will come on, but the system will not POST. I believe that this is probably the CPU, because the 4-pin supply powers the CPU. Is any way I can verify which component is bad without buying a new one of each, one at a time, and installing them?

Oh yeah, this first occurred when my old power supply died (I could smell electrical death in the guts). Before my old power supply crapped out, the system ran fine, and it had the 20-pin and 4-pin connected.

Posted by on

  • asphyxiate99 Mar 05, 2009

    Thanks for the input. Though I don't want to throw away a good CPU, if the motherboard is the only thing that's bad. Or vice versa. Any suggestions on how I can determine the culprit(s)?

  • asphyxiate99 Mar 05, 2009

    Good point. Thanks for the help. I think I might just do 'em both and maybe up my performance while I'm at it.



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It is more than likely that when your old power supply died a death, it damaged some components on the motherboard. Replace the Motherboard and chip, and you should be back in business. You can pick up some good value bundles to save money on buying the parts seperately. The power supply working again after turning off and on, is because there is a little trip in the power supply that triggers when it detects a fault. Powering down resets that trip allowing it to try and work again.

Posted on Mar 05, 2009

  • Jay Selway
    Jay Selway Mar 05, 2009

    Only by replacing one at a time - it's unlikely that the CPU will damage the board, it will just churn out garbage if it's not working right, and nothing will start. However, the board can affect the CPU more, so I would start by changing the board. Problem you have, is that you could replace the board, and then the CPU goes faulty after a while, due to damage already done shortening it's life.



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