Computer won't turn on

October 25, 2008 at 07:10:44
Specs: Windows XP, Intel P4

My computer suddenly turned off while I was using it, and now it won't turn back on.
I have checked and made sure that all the power plugs are tightly plugged in, and that the power is on.
When I press the power on button, the fan in the back of the CPU powers on, as does the fan on the processor. No lights (neither green nor red) adjacent to the power switch go on.
I have tried switching to another hard drive, as I have a spare one sitting inside the machine, but it didn't help.
My computer is a 4-year-old custom-built one. I'm not sure if the problem is with the motherboard (I have read that resetting it might help, but 1) I have no idea how to re-set it (my MB is Fujitsu Siemens D1675), and 2) if the processor fan powers on, does that mean the MB is ok?)
Help, please?

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October 25, 2008 at 07:27:45

"the fan in the back of the CPU powers on, as does the fan on the processor"

The CPU IS the processor. I believe what you're referring to as the "CPU" is the tower/case? The "fan in the back" is either is a case cooling fan or the power supply (PSU) cooling fan.

Why would you switch the HDD because of a power issue? If you haven't already done so, switch it back. And I doubt resetting the BIOS is gonna do anything unless you attempted to overclock & went overboard with the settings?

The 3 most likely candidates are the PSU, CPU or motherboard. You may ask why would the PSU be a possibility if the fans work? There are several different voltage rails (+3.3v, +5v & +12v) could be that just one of them fried leaving enough power for fans & lights, but not enough to boot an entire system. Unfortunately, power issues aren't easily diagnosed thru a forum. Make sure all you connections are tight & that there's no dust buildup within the case. You didn't try to remove the heatsink/fan (HSF) from the CPU, did you?

The bottomline is you have some troubleshooting ahead of you.

"If my answers frighten you then you should cease asking scary questions" - Jules Winnfield (Samuel L. Jackson) in Pulp Fiction

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October 25, 2008 at 07:32:19

You're right, I mean the power supply in the back -- that fan powers on ok, as does the actual CPU fan.
I switched the HD because I've had HD problems in the past, and I thought maybe they were at it again. I have switched it back to the original drive now.
I did not try removing the heat sink, since I have no idea how to do it.

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October 25, 2008 at 10:08:19

From the description, the first thing I would suspect is that the PSU failed. Computer PSUs provide multiple voltages, 12V, 6V, 3.3v, etc. That's why there are all those different wires connecting the PSU to the motherboard. The fans usually run on the 12V power bus, but the LEDs (lights) are usually powered by the 6v bus. The PSU may still be providing the 12v power running the fans, but not other voltages. The quickest way to test that theory is to try and get another PSU to swap out and see if the computer works again. It would be best if you could just use one temporily to test this before buying a new power supply and finding that it is not the problem.

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Related Solutions

October 25, 2008 at 12:24:50

Try booting up with the hard drive disconnected from the motherboard and the psu. You might also try removing all but one stick of RAM. Then see if it boots up and if you get into the BIOS, etc.

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October 25, 2008 at 14:04:35

I took out and put back in the MB battery. The computer still doesn't turn on, but now when I push the power on button, the LEDs next to it blink, in synchrony, until I turn the power off.

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October 26, 2008 at 06:18:21

"I took out and put back in the MB battery"

Like I said in my other response, swapping the HDD isn't gonna fix a power issue & neither is resetting the BIOS. The problem is either the PSU, CPU or motherboard & it's impossible for any of us to tell you have to troubleshoot.

"If my answers frighten you then you should cease asking scary questions" - Jules Winnfield (Samuel L. Jackson) in Pulp Fiction

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October 26, 2008 at 07:57:11

I suggest take the motherboard and the PSU out from the casing and put it in a clean isolated table, connect the PSU, motherboard with memory of course but without the hard disk or any drive. And then power it up. In that way you can narrow down the number of hardware which may have cos the problem. So its much more easy for you to diagnose. If the problem will not show try putting back together one at a time starting with the hard disk and so on but the casing will be the last to be put back.


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