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My Mother board has power but my computer will not turn on.?
Ok My computer wont turn on - no fans or anything - my motherboard is showing an led on it so I know there has to be power to it. Here is what I have done so far. Tried another power button - no success, replaced motherbaord CPU and RAM - no success - Took out all hard drives - no success took out all periferal boards and replaced video card with a known good video card - no success - replaced power supply with new one - same symptom but when I use the power button the fan on the power supple moves just a fraction of an inch but nothing else. The only thing left to replace is the case but as I am using a diffrent power button, that should not matter. I am even using a diffrent wall outlet that is known good. again the olny sign that I even have power is the led on the mother board comes on when I plug the power supply in. - Any ideas at all? I am clueless - Thanks
1) Unplug all external devices, including monitor, keyboard, and mouse. One of these devices may have a short, and cause the system to fail.
After everything is unplugged, try to turn on the system. It should at least give you some beeps, and the fan should come on, even without a keyboard, mouse, or monitor connected.
2) Unplug all hard drives, floppy, and CD drives.
Try powering up with these devices disconnected. Again, there should at least be some beeps, and fans should run.
3) Check all plug-in cards to make sure they are properly seated.
Note: When working inside the computer, you should connect a ground wire to the case, and wear a grounded wrist strap to prevent damage due to static discharge.
My method of doing this is to leave the computer plugged into the power strip, then turn off either the switch in back of the PSU (if there is one), or if there is not, turn off the power strip to which the computer is connected. You want to have the ground wire connected (through the 3-wire cord) but not have any power on the motherboard.
Note: Turning off the computer without switching off the PSU or the power strip does not remove power from the MOBO. There is always some power when the PSU is powered up, even when the computer is not running, thus your green LED being lit. Never remove or install internal components when there is power on the MOBO.
If you don't have a wrist strap, touch the computer case periodically to make sure you are not carrying a charge.
If you remove any cards, store them in special anti-static bags (the ones the cards came in) to prevent damage from static.
4) Check that the CPU is properly seated: Caution- Be very careful when doing this. Follow MFR instructions when removing/installing the CPU and heat sink.
Again, make sure that the machine, and you are grounded, and that no power is applied to the system.
5) Never remove power from the MOBO while the PSU is powered up. You said you pulled the 20-pin plug part-way out, and saw some life in the system.
This alone can blow things up. The MOBO is designed to run with all the PSU voltages at correct level. Having just one of them lower, or missing can cause system failure and damage!
If all of the above fail, I recommend a completely new system. I would be hesitant to try replacing the MOBO alone, considering the possibility that one or more of the cards (video, etc), or the CPU are bad, and may blow out a bran-new MOBO.
On the other hand, a bad MOBO could blow out a new CPU.
Good luck.
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