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    NP8760/W870CU - CPU fan mystery

    Discussion in 'Sager and Clevo' started by patternrecog, May 10, 2011.

  1. patternrecog

    patternrecog Newbie

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    My laptop was dropped while it was running a while back, and I later found it would boot up for a few seconds then restart. Opening it up I could see the CPU fan wasn't spinning, so I figured the fan had possibly broken.

    Switching it with the GPU fan however, I saw that the same thing happened (the GPU fan plugged into the CPU fan socket didn't turn). I then guessed it was either the power pins themselves, or something on the motherboard related to control of the fan.

    $850 and a new motherboard install later, and I have the same issue! Whatever fan is plugged into the CPU fan pins doesn't turn. In desperation I started running the fan from an external power adaptor (stripping the wires, then taping them into the small molex). I also cut the yellow wire in the hope it wasn't just an RPM meter and was actually used as a control signal that had gotten stuck. No dice.

    So with everything I thought would be related to the fan power pins replaced or switched out for working versions, what is happening here? The only thing I can think of now that would have anything to do with the fan is the silent mode button - but could that really drop the fan to 0%? And with all the times I've opened it up now, would disconnecting it make any difference? I've plugged and unplugged many times in this process it so its unlikely to be a bad seating on the ribbon/plugs in that area.

    Also does anyone want to buy an apparently fully functional motherboard? haha.
     
    patternrecog, May 10, 2011
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  2. MifuneT

    MifuneT Notebook Guru

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    If I were to make a wild guess, something is grounding itself out. Look at connections and wires to the power button. Connect the fans to a regular working desktop computer just to ensure that the fans are working.
     
    MifuneT, May 10, 2011
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  3. patternrecog

    patternrecog Newbie

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    I've tested the fans using external power sources (and the GPU pins) and they're both working. I'm actually posting onthe laptop now, running power to the CPU fan from an external adaptor, so I know everything else its fine. Its just how this problem can persist across different motherboards that has me scratching my head.
     
    patternrecog, May 10, 2011
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  4. Aikimox

    Aikimox Weihenstephaner!

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    Did you replace the mobo yourself or send it to someone?
     
    Aikimox, May 11, 2011
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  5. patternrecog

    patternrecog Newbie

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    I replaced it myself - its a pretty straightforwards job. I thought a up could be a possibility, but the odds of the exact same problem (one being caused by dropping, the other by poor installation) happening twice indepenently were pretty slim

    edit: going in to disconnect the LED panel buttons (including the silent mode button)...
     
    patternrecog, May 12, 2011
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