Can a bad mobo damage a good power supply?

Discussion in 'A+ Certification' started by Captain Lon, Jul 6, 2005.

  1. Captain Lon

    Captain Lon Guest

    I have a computer that is damaged due to a near-by lightning strike.

    I tested the power supply with my little power supply tester, and it shows
    no -5v leg, and a red 'danger' light comes on. So, I replace the power
    supply with a new one, plug the puter back into the wall, hit the button,
    and guess what? Nothing, that's what. I put the new power supply on my
    little power supply tester and it shows the exact same thing as the 'known
    bad' power supply showed, no -5v leg and a red 'danger' light comes on.

    What gives?

    I did not check the new power supply to make sure that it was good before
    installing it, therefore there is a chance that the new power supply was bad
    all along.


    is there anything in the mobo (or elsewhere) that would damage a good power
    supply in this way?

    I don't want to install yet another power supply if there is a chance that
    it can be damaged, too.

    Thanks, y'all.
    Captain Lon, Jul 6, 2005
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  2. Did you check the supply under load? Switching power supplies need
    about 10% of rated load on the +5 at least, and possibly other legs as

    Yes, a bad motherboard can damage a power supply.

    Tom MacIntyre, Jul 6, 2005
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  3. Captain Lon

    Captain Lon Guest

    Tom wrote: > Did you check the supply under load?

    How would I do that in this situation? I did not have a working computer,
    so I am puzzled as to how to go about this.
    Captain Lon, Jul 6, 2005
  4. A different motherboard with the same or similar PS requirements.
    Sometimes you can get away with using automotive bulbs or the
    appropriate resistor values, but they'd have to be calculated based on
    the PS, and they'd probably get a little hot also.

    Tom MacIntyre, Jul 6, 2005
  5. Captain Lon

    AG Guest

    Hey Tom. A good power supply tester is the load. Mine is designed to be
    plugged into the MB plug and gives a load so that the supply comes on. It's
    not a good idea to leave it on for long. The instructions on the tester say
    not to and it does get pretty warm but it gives me a green light if all of
    the voltages are right.

    AG, Jul 7, 2005
  6. Captain Lon

    w_tom Guest

    First, a power supply can test just fine on those testers
    and still fail in the computer. The best load is a computer.
    The best tester is a 3.5 digit multimeter that also provides
    essential numbers. Numbers that report more about that power
    supply's health AND other parts of the power supply system.
    The power supply system is not just a power supply.
    Summarizes of how to check a power supply were posted
    previously in:
    "Computer doesnt start at all" in alt.comp.hardware on 10
    Jan 2004 at and
    "I think my power supply is dead" in alt.comp.hardware on 5
    Feb 2004 at .

    In your case, most important first numbers are from purple
    wire before powering computer and from purple, gray, and green
    wire after power button is pressed.

    Second, can motherboard damage a power supply? No, as
    others have stated. Correctly posted was a reply even 30
    years ago. Short together all power supply outputs, and still
    the supply must not be damaged by that short circuit. Power
    supplies even 30 years ago protected themselves from load

    Function (that the power supply manufacturer should have
    provided in writing) is called overpower protection. However
    power supply manufacturers that are missing essential and
    required functions also forget to provide written specs.
    Claim nothing and one cannot be held liable for the defective
    product. Therefore inferior supplies forget to provide
    written specifications.

    There is no faster way to confirm the integrity of, or
    locate the defective component in your power supply 'system'.
    Get a meter and have important numbers in but two minutes.
    Even if those numbers mean nothing to you, to others those
    numbers provide far more information than yet posted. Without
    those numbers, currently, your responses are mostly
    w_tom, Jul 7, 2005
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