• Creator
  • #2210795

    Faulty PC – No signal on the Monitor, Keyboard and Mouse?


    by dolphin111 ·

    Hello everyone,

    I have a PC (HP Compaq dc7900 Small Form Factor) which stopped working. The power light is on and green, the light on the motherboard is also on and green, Power Supply is running, i can tell that from the lights that are on and the spinning fan at the back of the power supply itself.When i plug in the power cable to the power supply the CUP Fan starts spinning and all the lights in the front panel goes on, but there is no display in the monitor, no any signal in the keyboard as well as on the optical mouse. I unplugged everything and started putting back each device one by one, still to no avail. Tried changing CPU, no success.

    One question, why is it that when i plug the Power cable to the power supply everything starts running without hitting the power button at the front panel?

    I have searched for any similar issue of this PC on the net i found nothing, am i so unlucky to be the first one to experience this fault?

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  • Author
    • #2901173


      by dolphin111 ·

      In reply to Faulty PC – No signal on the Monitor, Keyboard and Mouse?


    • #2901167

      Motherboard or Power Supply

      by thechas ·

      In reply to Faulty PC – No signal on the Monitor, Keyboard and Mouse?

      The only way to test a power supply is with a load. Then, verify that all of the DC voltages are within limits. While I do have a power supply tester, I often just swap supplies that I think may be bad.

      That said, it sounds like the motherboard itself has failed on this system. The first thing I do when I suspect a bad motherboard is to look at all of the capacitors. They should all be round cylinders with flat or slightly concave tops. If the tops or sides have bulged, or if there is evidence of something leaking from the bottom of the cap, you have proof that the motherboard has failed.

      Based on your symptoms, even if the caps look good, I would suspect that this motherboard has failed. Salvage what you can and either build up a bare-bones system, or look for a used system that meets your needs.


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