PC turns on and off repeatedly

Hi until recently, my pc was running fine! then, it would boot but only stay functional for a few mins then freeze.Now it just turns on and off again repeatedly? Ive removed all the parts except the gpu, cpu + fan and still get no vga as it cycles on/off. The board is out of the case and still the same.PSU has been changed. The weird thing is when I remove the 4 pin atx plug, it stays on but no vga/post!
please help!
core 2 e8400
p35 asrock twins
corsair dominator ddr 2
650 watt psu
9 answers Last reply
More about turns repeatedly
  1. Test your ram one stick at a time. Could be a bad stick or bad ram slot. If you change boards, I recommend another asrock in the p45 chipset. This could save you from having to format your hardrive. Asrock makes good products; their failure rate is no worse than other brands. I've used them all.
  2. ok ive tested without memory and different working ram, still no post! do u think its the board then?ive even tested the on off switch for shorts no problem except for the recurring on off cycle.
  3. Generic power supply? I saw the word "corsair" and associated it with your power supply. My bad. Corsair makes great power supplies. You need to list your brand and the 12v rail ratings in amps. Cheap power supplies could cause your symptoms.
  4. Hi I tested the PSU, in particular the 4 pin atx plug with a multimeter and Im getting a consisitent 12.14 out of each pin? I have changed the psu to known working ones but to no difference. Why does the pc stop cycling on and off when the 4 pin atx plug is disconnected? At this point I get no VGA still.
  5. sounds like a lack of power on the 12v rail causing the PSU to power down as more is trying to be drawn than it can provide. You say you'cve tried a known good PSU? What PSU? What GPU?
  6. What brand of PSU? It makes a huge difference.

    Quote:
    Hi I tested the PSU, in particular the 4 pin atx plug with a multimeter and Im getting a consisitent 12.14 out of each pin?

    Is that with the cable plugged into the motherboard? If not, there's little load on it. And the reason you get the same voltage out of each pin is that the two lines are wired in parallel back at the PSU.

    Quote:
    I have changed the psu to known working ones but to no difference.

    Of similar capacity?

    Quote:

    Why does the pc stop cycling on and off when the 4 pin atx plug is disconnected?

    With the 4 pin plug removed, you have no power going to the CPU, so the system isn't even trying to start.
  7. the 2 psu's i tested are 600w and 650w..... both of them in another pc, (dfi nf 4, 939socket, mushkin cl3)...no probs in that setup stays sober! its my back up till I get mine fixed
  8. what PSUs?
  9. ez cool socket 775 specific
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