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Does This Sound Like Problems With Motherboard?

By mrkeebo
Sep 17, 2006
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  1. Hi All,

    I just received a refurbed PC I purchased through UBID. The PC is an HP Media Center. Upon installation the PC worked fine for about 15 minutes then abruptly shut off. I attempted to restart with no success.

    I noticed that each time I pushed the on/off button on the front of the tower, the power supply light would go off on the back of the tower. I removed the panel and checked all connected of the cables running from the power supply. All were securely plugged in.

    I then unplugged the cables running from the power supply one by one and attempted to power up the PC. When I unplugged a cable indentified as P7 from the motherboard (this is a small plug with 4 wires) the power supply works fine. If this cable is connected, the power supply immediately quits.

    Does this sound like a faulty motherboard, or possibly a faulty cable? What further diagnostics can I do to be sure?

    Thanks,
    Kee
  2. Rik

    Rik Banned Posts: 4,985

    What colour cables are in the P7 connector and is the main power supply unit (psu) a 20 pin connector?
  3. mrkeebo

    mrkeebo TS Rookie Topic Starter

    Rik,

    The four cables consist of two yellow and two black cables. The power supply has a 20 pin connector.

    Thanks,
    Kee
  4. Rik

    Rik Banned Posts: 4,985

    The 2 yellows are +12volts and the 2 blacks are ground. Do you have a test meter?
  5. mrkeebo

    mrkeebo TS Rookie Topic Starter

    Rik,

    Do you mean an ohms meter? I do have one.

    Thanks,
    Keith
  6. htetickrt

    htetickrt TS Rookie

    Same problem here

    Not to horn in on Keith's question, but I have the exact same problem with a different system.

    I've had this Athon 64 3000+ build for about 2 1/2 years now, with no problems; then one day in the middle of an e-mail it up and shuts off on me, refusing to turn back on. I've detached every piece of hardware from the motherboard, including the CPU, with no effect.

    With just the 20-pin power supply connector, the fans run, there is power to the motherboard, and the motherboard lights inform me that the CPU is not posting (as one would expect it not to with no power and now no chip). However, the minute I plus the extra 4 pin 12V supply in to the motherboard, the whole thing shuts off. The 4 pin connector reads 12V when the 20 pin connector is plugged in.

    Any ideas? The MB is an MSI K8T Neo. My guess is the same cause is responsible for both our problems, but I don't know what it is.

    Thanks!
  7. Rik

    Rik Banned Posts: 4,985

    I am currently attempting to help mrkeebo via msn messenger. If we get to the bottom of the problem then i will post up the results in this thread. I can help you out the same way if you like, if you want to do that then say so and i will give you my msn details in a private message. Mrkeebo is in the process of testing everything out thoroughly, we are not doing this on techspot as i don't wish to encourage anyone to carry out power supply tests without supervision. Basically, i don't want to encourage people to risk electrocution.
  8. htetickrt

    htetickrt TS Rookie

    Thanks greatly for the offer, but you sound like you have your hands full. Anyway, I'm pretty sure my problem is not with the PS; I connected an older 300W one from another working computer (this one) and the same problem happened, but that PS clearly works (otherwise I couldn't be typing this).

    I'll watch the thread though to see if you find a problem unrelated to the PS, though. I 'm just trying to avoid either shelling out money for an old MB or even more money for a new MB and lots of other new pieces. I'll also write to this thread if I figure it out.

    Thanks!
  9. mrkeebo

    mrkeebo TS Rookie Topic Starter

    Rik,

    I've tested with the meter and all wires test correctly (either 3.3, 5, or 12 depending upon color).

    Thanks,
    Keith
  10. Rik

    Rik Banned Posts: 4,985

    Ok, that means the psu probably isnt at fault here, next thing is to check your mobo out thoroughly.
  11. kirock

    kirock TS Rookie Posts: 1,598

    Mrkeebo try this procedure in order to make sure your mobo, case switch and PSU are working correctly. It might be the power button on the case or a failing PSU or something more drastic like a dead CPU. A dieing PSU might still put out the correct voltages but as soon as it's loaded (i.e. plugged to the mobo) it fails.

    The 4 pin connector you are talking about is what powers the CPU, so if the cpu has failed it might "pull" the PSU to ground thus kicking in it's automatic shut down.
     
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