Member Avatar for simsiesims

Hi folks, I'm really sorry if this has been asked before.

Several months ago (yes, it's been a long time but it's about time I get it fixed) I had a problem with my XP PC. When I hit the power button, the fan moves for a fraction of a second and the power goes on and off and on and off constantly until I finally have to unplug it. It wont actually start up at all.

Anyone know anything about this at all?

Any help would be amazing.

Adam

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  • Latest Post Latest Post by sittas87

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The symptom described — the case fan and lights flick on for a fraction of a second then the system cycles off/on immediately — most often means the power delivery is being shut down by a protection circuit or the motherboard is shorting. and were right to point toward power-related causes, but there are a few practical checks that help isolate the exact fault without swapping parts blindly.

Quick diagnostic workflow:

  • Power down and unplug. Visually inspect the motherboard and PSU for bulging or leaking capacitors, burn marks, or loose standoffs/screws that could short the board.
  • Reduce to a minimal configuration: CPU + cooler, one stick of RAM, onboard video (or single GPU), CPU 4/8-pin and main ATX plug connected. Remove drives, extra cards and peripherals. Try powering the board on outside the case (bench test) to rule out a case short.
  • Test the front-panel switch: disconnect the case power-switch header and briefly short the two motherboard power pins with a screwdriver; if it starts, the switch or front-panel wiring is at fault.
  • If comfortable, use the paperclip method to spin the PSU up by shorting PS_ON (green) to any ground (black) on the 20/24-pin, then measure rails with a multimeter: yellow = +12V, red = +5V, orange = +3.3V. Expected tolerances are about +/-5% (12V ~11.4–12.6V, 5V ~4.75–5.25V, 3.3V ~3.135–3.465V). Do not open the PSU.

If rails are good but the bench test still cycles, the motherboard or CPU is the likely failure. Always unplug mains before touching components, avoid opening the PSU, and get a shop to help if unsure.

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Member Avatar for simsiesims

Hi folks, I'm really sorry if this has been asked before.

Several months ago (yes, it's been a long time but it's about time I get it fixed) I had a problem with my XP PC. When I hit the power button, the fan moves for a fraction of a second and the power goes on and off and on and off constantly until I finally have to unplug it. It wont actually start up at all.

Anyone know anything about this at all?

Any help would be amazing.

Adam

Ooh and can I also add (if it's any help) that this is immidiate. Happens the second the power button is hit.

Member Avatar for coolraj003

I think you ll have to check your powers upply as it might be having someissues with the circuit getting shot and causing fluctuations and by the sounds of what you are saying it is very deadly for the life of your mobo specially as if it goes on and off like that it wont be long that the mobo would get fried.

Check your system with a different power supply and see that all the connections inside the system are stable as well. Just pull em out and plug em in again. see if that works.

Raj

Member Avatar for sittas87

hi
do as raj suggested replace your psu there might be sortage of power.a clever step will be to test your failed psu in another machine if you cant seem to get hold of a good psu immediately
good luck
??

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