Motherboard dead? Light comes on but thats it

Discussion in 'Computer Support' started by BertieBigBollox, Sep 2, 2007.

  1. Power LED on mobo comes on but nothing when you hit the power button.
    Can I assume the mobo is dead?

    Also, just to rule out a power button problem, is it acceptable to
    short (with a jumper) the two-pin power button header on the mobo to
    force a power on that way?
     
    BertieBigBollox, Sep 2, 2007
    #1
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  2. BertieBigBollox

    meerkat Guest

    Prove the PSU first.
    Yes to the second question.
     
    meerkat, Sep 2, 2007
    #2
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  3. Same result with a new PSU as well...

    How would you test a PSU?
     
    BertieBigBollox, Sep 2, 2007
    #3
  4. BertieBigBollox

    meerkat Guest

    A test meter from, say, Maplins.
    That way you can test the PSU with it switched on (under load)
    to see if it`s delivering the correct voltages.

    As for the other supply you tried, was it adequate for the job ?.
     
    meerkat, Sep 2, 2007
    #4
  5. Initial PSU was a 250W Bestec, the new one is a 350W one...

    Assuming the new one PSU is OK, would you assume the mobo is indeed
    dead?
     
    BertieBigBollox, Sep 2, 2007
    #5
  6. BertieBigBollox

    John Holmes Guest

    "contributed" in 24hoursupport.helpdesk:
    Stick your fingers in it and switch it on. If your hair starts pointing
    towards the ceiling, the PSU is OK.
     
    John Holmes, Sep 2, 2007
    #6
  7. BertieBigBollox

    meerkat Guest

    You can`t `make assumptions` can you ?.
    You need to Know you`re getting your correct voltages under load.
     
    meerkat, Sep 2, 2007
    #7
  8. BertieBigBollox

    Shel-hed Guest

    No. Reseat all cards and memory. Try disconnecting or removing all unnecessary
    items.
    Google motherboard capacitors and look for pics of blown caps to see if that is
    your problem.
     
    Shel-hed, Sep 2, 2007
    #8
  9. OK. First PSU wont even power on with Pin 14 shorted - so thats
    knackered for starters.
     
    BertieBigBollox, Sep 2, 2007
    #9
  10. BertieBigBollox

    Pennywise Guest

    There is a green wire you can short to any black wire to power on the
    PS.

    Best to do this in place so the PS has a load, just use a paper clip
    to short green and any black.
    www.bluemax.net/techtips/ATXPowerSupplyWiring/ATXPowerSupplyWiring.htm
     
    Pennywise, Sep 2, 2007
    #10
  11. BertieBigBollox

    SgtMinor Guest

    Your motherboard manufacturer may have some hints. Asus shows a
    sequence of steps to take:
    http://support.asus.com/troubleshooting/troubleshooting.aspx?SLanguage=en-us
     
    SgtMinor, Sep 2, 2007
    #11
  12. BertieBigBollox

    Drag~~~~~on Guest

    Whatever you do, don't take to a shop for repair paul!
     
    Drag~~~~~on, Sep 2, 2007
    #12
  13. BertieBigBollox

    Drag~~~~~on Guest

    Whatever you do, don't take to a shop for repair Paul!
     
    Drag~~~~~on, Sep 2, 2007
    #13
  14. BertieBigBollox

    Vanguard Guest

    BertieBigBollox wrote ...
    Did you have a load on that PSU? Shorting PS-ON to ground on the 20-
    or 24-pin power connector (from PSU to mobo) may not get the PSU to
    power on. The PSU may be smart enough to know there is no point in
    powering up completely if there is no load on it. Add a working hard
    drive on one of the power taps from the PSU. Make sure none of the
    taps from the PSU are connected to anything other than the test hard
    drive. Then short PS-ON (pin 14, green wire) to ground (a black
    wire). With a hard drive connected, do you see and hear the fan
    inside the PSU is spinning? Does the hard drive spin up?

    I have yet to see mention that this computer ever did power up before.
    You never mentioned if this was a working system or something you just
    put together and it has yet to work. If it was a working computer
    before, what did you change that then caused the computer not to power
    up? Did you add some other hardware?

    You said the "power LED on the mobo" lights up when you connect the
    old or new PSU to the motherboard. And which LED is that? The one on
    the front of the case? Or an LED on the motherboard?
     
    Vanguard, Sep 2, 2007
    #14
  15. Yes. It was a working PC. Its a friends PC that has now stopped
    working.

    Apparently, the fan was making a noise and then it stopped working
    altogether.

    The LED on the actual mobo lights up.
     
    BertieBigBollox, Sep 3, 2007
    #15
  16. Tried this.
     
    BertieBigBollox, Sep 3, 2007
    #16
  17. BertieBigBollox

    Vanguard Guest

    BertieBigBollox wrote ...
    WHICH fan stopped working? There are rarely less than 3 fans: CPU,
    PSU, and 1 case fan. If it was the CPU fan, the BIOS will see the 3rd
    wire (yellow) from the CPU fan effectively returning zero RPMs which,
    to the BIOS, means that fan isn't spinning. If the CPU fan looks like
    it isn't spinning, the BIOS immediately powers down the computer to
    prevent the CPU from frying.

    If you test the PSU using the PS-ON to ground short, you need to
    disconnect the PSU from everything except the hard disk used as a
    load. If, for example, the CPU fan wasn't spinning then the BIOS
    shuts down the PSU but that would only happen if the 20- or 24-pin
    connector from the PSU was attached to the motherboard.
     
    Vanguard, Sep 3, 2007
    #17
  18. Dont know which fan. Like I said its a friends PC and I can get any
    sense. They said the fan was very noisy so its probably the PSU fan I
    guess - there is no case fan.

    So, I suppose it could just be a dead CPU fan?
     
    BertieBigBollox, Sep 3, 2007
    #18
  19. BertieBigBollox

    JAD Guest

    ALL power connectors are in place?
    Remove all hardware except PSU -CPU/HSF -1 stick of memory -video. Make sure the 3 pin fan
    header, reserved for the CPU is connected to the CPU fan.
    Will it boot?
     
    JAD, Sep 3, 2007
    #19
  20. Yep. Its an Intel socket 478 board so one 20-pin main connector and 1
    square 12v power.

    Tried as you suggest - still nothing. LED light on the mobo but
    nothing when I short the power on pins (PSU doesnt start up or
    anything elsee).

    If the CPU fan is the problem, would this display the same symptoms?

    Or is it looking more like u/s mobo?
     
    BertieBigBollox, Sep 3, 2007
    #20
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