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Mobo won't power on - 8 pin CPU atx 12v?

Discussion in 'General Hardware' started by LifeOnMars, Jan 31, 2010.

  1. LifeOnMars

    LifeOnMars New Member

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    Now here's what I've found: I can connect the 24 pin ATX power cable and the entire computer will turn on: the fans and everything else is running, all except for the CPU which isn't receiving power and the graphics card doesn't spin up. As soon as I plug the 8 pin ATX 12v cable that's supposed to power the CPU, the computer will no longer turn on. It'll turn on for a milisecond and instantly turn itself off.

    I am using -

    antec 900
    fsp everest 800w psu
    p5n-t deluxe mb
    q6600 go
    true 120 cooler
    4 gb xms 2 corsair 800
    320 gb seagate sata ii HD
    bfg gtx 275 oc

    so what could be the problem guys? Grounding issue?psu? Dead mobo or CPU?

    What's the minimum you need for it to power up, for example would it power on without the graphics card in place?

    It someones old system that I have bought so I know all the components have worked together.
     
  2. LifeOnMars

    LifeOnMars New Member

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    Anyone help in anyway on this please?
     
  3. theonedub

    theonedub habe fidem

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    You will need a GPU since there is not an onboard solution. Try using the 4pin 12v AUX plug instead of the 8pin and see if it does the same thing. Are you sure the GPU is installed correctly and plugged in as well? As always try it with CPU, GPU, 1 stick of ram, no HD, and see if you can get it to enter the BIOS.
     
    Crunching for Team TPU
  4. Mussels

    Mussels Moderprator Staff Member

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    mobo, PSU, ram, video card. Thats the minimum for a power on.

    the fact that its turning on then off again, means its detecting something is wrong - likely, you forgot something.
     
  5. LifeOnMars

    LifeOnMars New Member

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    Hi and thanks for the reply. It comes with two 4 pin plugs and I have tried it with both, and each one on their own all with the same result. Without any CPU power plugged in the psu fan spins, the case fans spin, the fan mounted to the true spins, the DVD has power, but the graphics card does not spin. When CPU power is added it turns on then instantly off
     
  6. LifeOnMars

    LifeOnMars New Member

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    Hi mussels. I have 24 pin, 8 pin atx, two pcie 6 pins, case power switch connection, ram in place, case fans, CPU fan all connected... Anything I have missed?
     
  7. Mussels

    Mussels Moderprator Staff Member

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    that list just confuses me :p


    Motherboard: 24 pin, 8 pin, any aux power it needs (floppy/molex connectors, some boards have em)
    Video card: all PCI-E power connected
    Ram: one stick, try various slots. if no luck, try another stick in several slots.

    During this, everything else should be disconnected. no HDD's, no DVD burner, no fans except for PSU, CPU and VGA.
     
  8. LifeOnMars

    LifeOnMars New Member

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    Sorry for any confusion :) as the true is passive it's ok to try turning on the system without it's mounted fan isn't it?
     
  9. theonedub

    theonedub habe fidem

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    Unless that board has a feature where it does not power on if there is no fan connected to the CPU Fan header. Might want to check that out.
     
    LifeOnMars says thanks.
    Crunching for Team TPU
  10. Mussels

    Mussels Moderprator Staff Member

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    ^ what he said.

    make sure the fan you use has an RPM sensor as well, or it wont detect it. (hint: use the fan from the stock cooler)
     
  11. LifeOnMars

    LifeOnMars New Member

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    Also if I have no joy with the above suggestions is it worth setting the whole thing up outside the case to make sure the case is not shorting it out?
     
  12. Mussels

    Mussels Moderprator Staff Member

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    yes.
     
    LifeOnMars says thanks.
  13. LifeOnMars

    LifeOnMars New Member

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    Ok just tried it all outside of the case and tried it with 4 different sticks of ram in all 4 slots individually. Exactly the same outcome :( but hopefully at least, that rules out any shorts happening inside the case. I also cleared the CMOS a few times just to check that as well. I have another psu arriving Monday so hopefully that may solve the problem or at least narrow the cause of the problem down a bit.
     
  14. Mussels

    Mussels Moderprator Staff Member

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    the only real thing left for you to do, is swap components with known good ones - test CPU, ram, PSU, and video card in another machine for example.
     
  15. LifeOnMars

    LifeOnMars New Member

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    Yeah and that's where things really suck. I've had to wait ages to afford to get this and then this:( well hopefully I can eliminate the power supply tomorrow and then take it from there...I'm absolutely gutted but that's life I guess. Thanks for the help so far guys and I'll keep updating the thread with any success or findings.
     
  16. dr emulator (madmax)

    dr emulator (madmax)

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    hm .gif you haven't got the 8 pin mobo plug mixed up with your pciexpress plug? that would spell smokin mobo
    have you tested the psu with a multimeter in situ?
     
  17. LifeOnMars

    LifeOnMars New Member

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    Nope no mix up on the plugs. Don't have a multimeter and can't really buy anything else at the moment so I'm stuck. Another member from the uk has said he will help by testing components on his system so will try new power supply tomorrow and if there is no joy I'll start posting him stuff to test out for me...that's if I can afford postage,yes, it's that bad.
     
  18. dr emulator (madmax)

    dr emulator (madmax)

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    shame ya don't live near me :ohwell:
     
  19. LifeOnMars

    LifeOnMars New Member

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    I moved here recently and don't really know anyone locally although I think alexp one of the moderators lives around my neck of the woods.
     
  20. LifeOnMars

    LifeOnMars New Member

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    I'm bored so I'm gonna remove the thermalright ultra and clean it. The idiot who shipped the computer left it attached so whilst I have it removed I'm going to check the CPU and socket for any damage. As I have only used amd previously is there anything that would signify damage to the processoer or the socket? also what's the best thing to use for cleaning the thermalright ultra, I was just going to use a cotton bud to clean all the dust of it, is that ok?
     
  21. brandonwh64

    brandonwh64 Addicted to Bacon and StarCrunches!!!

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    look for bent pins in the CPU socket and if there is then thats your culprit
     
    LifeOnMars says thanks.
    Crunching for Team TPU
  22. Bo$$

    Bo$$ Lab Extraordinaire

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    plug in the cpu 8pin,take out the graphics card, does it still turn off?
     
  23. LifeOnMars

    LifeOnMars New Member

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    Cheers brandon for your continued support mate
     
  24. brandonwh64

    brandonwh64 Addicted to Bacon and StarCrunches!!!

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    YW. this problem seems like as i said in the other thread that it could be a bad motherboard or a corrupted bios but its hard to tell. if you can find another motherboard or CPU to test that would be best
     
    Crunching for Team TPU
  25. dr emulator (madmax)

    dr emulator (madmax)

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    ye it's a shame you don't live near here, as i would have been able to whisk that cooler of to my uncles garage, and use the air compressor to blast the dust out , if it's aluminium i would wash it under the tap then use a hair dryer to dry it out
     

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