Power Supply vs. Motherboard

Discussion in 'A+ Certification' started by smackedass, Feb 20, 2007.

  1. smackedass

    smackedass Guest

    Hello again,

    I had been under the impression that if a Windows computer won't boot, and
    you've checked the memory sticks and other basics, such as the power cables
    plugged in properly, that it's either the mobo or the power supply.

    I spoke with a chap at Dell the other day, and he told me that if you plug
    the power into the wall, and into the power supply, and if the motherboard
    light lights up, the problem is ALWAYS the motherboard. He also told me
    that if the light does not light up, the problem is ALWAYS the power supply.

    I'm under the impression that these statements may qualify as "maybes", but
    not "always'"

    smackedass, Feb 20, 2007
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  2. smackedass

    smackedass Guest

    smackedass, Feb 20, 2007
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  3. smackedass

    Gerard Bok Guest

    Well, call it an educated guess.

    PSU pretty much is a go/no go part. If the led on the mobo lights
    up, the PSU must be a 'go'.
    So blame the mobo :)
    Gerard Bok, Feb 20, 2007
  4. smackedass

    smackedass Guest

    That seems logical enough. Almost too logical. Thing is, I don't have the
    proper power supplies and motherboards sitting around in my basement. I
    have to order them, and have the parts mailed to me. And, it would suck if
    I ordered a motherboard, when I needed the power supply, or vice versa.

    It's one thing if a person is having trouble getting a network connection, I
    have about 20 network cards sitting around that I could use to troubleshoot.
    Not the case with power supplies and mobos, there are so many form factor
    differences, not to mention proprietary differences.

    smackedass, Feb 20, 2007
  5. smackedass

    Gerard Bok Guest

    As you specifically mentioned Dell: keep in mind that they do
    sometimes use off-standard powersupply wiring!
    (Plug fits, wiring doesn't !)
    Gerard Bok, Feb 20, 2007
  6. smackedass

    Rod Speed Guest

    You're right, he's wrong.

    Not just the motherboard or power supply either, it can be something
    as basic as the front panel switch not connected to the motherboard too.
    Rod Speed, Feb 20, 2007
  7. smackedass

    Mister Guest

    Buy a power supply tester. It costs about $15 and work very well.
    It has a series of LEDs on it and it will tell you which leg of the
    power supply is defective. ie. +5, -5, +12 or -12V
    Mister, Feb 20, 2007
  8. smackedass

    smackedass Guest

    I was hoping and praying that such a thing existed. Can you give me a link
    to something that you would recommend?


    smackedass, Feb 21, 2007
  9. smackedass

    Patrick Q Guest

    I bought one, but DELL told me never to use it. I was to use the paperclip
    on the Green and Black terminals....If the fan spun, it worked. I do
    warranty work for Dell... Funny, though, everytime they send me out to
    replace a motherboard, they send a power supply too. :)
    Patrick Q, Feb 21, 2007
  10. smackedass

    smackedass Guest

    I do
    That's telling.

    smackedass, Feb 21, 2007
  11. smackedass

    w_tom Guest

    It only tells you that sending a power supply - just in case - is
    cheaper than having him driver there twice.

    Meanwhile the power supply tester - and this should be obvious to
    those with basic electronic knowledge - is woefully insufficient to
    test a power supply. That tester can only identify a bad supply;
    cannot identify a good supply.

    However two minutes with a meter - and not disconnecting anything -
    can confirm or condemn the power supply system. Yes, a 'system' where
    a power supply is only one part of a 'system'.

    Essential is a tool so ubiquitous as to be sold even in Kmart. A
    tool as complex as an Ipod. A tool as necessary as a screwdriver.
    That 3.5 digit multimeter is sold even in Wal-Mart, Sears, Lowes,
    Radio Shack and Home Depot.

    Two minute procedure is posted in "When your computer dies without
    warning....." starting 6 Feb 2007 in the newsgroup alt.windows-xp or

    What is the most important fact when locating the failure?
    Numbers. Numbers not only are necessary to define what is and is not
    working. Numbers are also necessary to get replies here that are more

    The procedure does what is repeatedly defined in the CSI shows.
    Follow the evidence. So many previous posts were classic
    shotgunning. It did not solve the problem AND you learned nothing
    new. Just another reason why shotgunning costs more money, takes
    longer, and can even exponentially complicate a simple problem.
    w_tom, Feb 22, 2007
  12. smackedass

    Mister Guest

    I could have mentioned the tongue test, but instead I suggested the
    power supply tester.

    5 out of the 5 times it said the power supply was bad, the power
    supply was really bad.

    Someone wanted numbers. These might not be numbers from a meter, but
    these are numbers that look like some good odds to me that it works
    perty well.

    Abreviation to live by: K.I.S.S.

    Yo w_tom - rag time? sheesh!

    Here's that link you asked for:

    There are others on eBay that might be cheaper.

    If you are going to get a multimeter, might I suggest this one:

    Just joking...

    Mister, Feb 22, 2007
  13. smackedass

    smackedass Guest

    Thank you to all who have responded.

    Someone mentioned that I haven't learned anything out of these exchanges;
    that's hardly the truth. Though it is useful to be reminded how dumb I can

    smackedass, Feb 22, 2007
  14. smackedass

    smackedass Guest

    I've got plenty of all of those items down in the dungeon. But with so many
    different form factors and sizes of power supplies, it's hard to have one
    "known good/good for all".

    The multimeter is what I needed to be reminded of.

    Next...how to troubleshoot a processor vs. a mobo...

    smackedass, Feb 22, 2007
  15. smackedass

    smackedass Guest

    My lapse in judgement here, was taking for granted his (inferred) statement
    that all motherboards have LEDs.

    Still if the
    Now expecting the wrath of the better informed...as I mentioned above, I'm
    now interested in knowing how to troubleshoot a processor vs. a mobo.

    smackedass, Feb 22, 2007
  16. smackedass

    Mister Guest

    Hook a 3.5 digit multimeter, that is sold in Wal-Mart, Sears, Lowes,
    Radio Shack and Home Depot, to the processor. :)
    Mister, Feb 22, 2007
  17. smackedass

    Gerard Bok Guest

    Simple. Replace the CPU. If that solves the problem, the (old)
    CPU was the culprit.

    If that doesn't solve anything, explain your client the benefits
    of either a new system or an upgrade kit (Mobo - CPU - Ram) for
    his current system.
    Unless you work for free, you won't get many satisfied clients by
    trying to float an already unreliable system :)
    Gerard Bok, Feb 22, 2007
  18. smackedass

    w_tom Guest

    Power supply tester complicates the problem. Spend as much money as
    for a meter, then complicate the problem by disconnecting, and still
    not have a clear answer. If power supply is completely dead as
    stated, then even a paper clip reported same thing. If an incomplete
    answer is sufficient, then paper clip is the K.I.S.S. solution. Power
    supply tester therefore violates K.I.S.S. Why then spend so much
    money for a tester?

    Worse, power supply tester cannot report a power supply as good. It
    can only report power supply as bad by doing same thing that a paper
    clip discovers. K.I.S.S. A valid diagnostic tool reports something
    as either good or bad. Power supply tester does not do that. Power
    supply tester requires as much money and more labor to get an
    incomplete answer. K.I.S.S. is the simple solution 30 years ago when
    meters were also used.
    w_tom, Feb 22, 2007
  19. smackedass

    JohnO Guest

    This being an A+ newsgroup and all, it's worth pointing out that there
    are no meters or volts on the A+ exams. As a result, most computer
    repair techs don't have a lot of electronics training. IMO the subject
    should be there, but that's my background so I'm biased.

    The PS testers have their place, so long as you are aware of their
    limitations. On a field service call they might not be so useful, but
    in a depot repair center there's no faster way to identify a dead
    supply unless you use (or build) a fixture that includes loads and
    meters for each output. Dismissing PS testers completely is a mistake
    in this forum.

    -John O
    JohnO, Feb 22, 2007
  20. smackedass

    smackedass Guest

    I only wish that there had been more, much more, about electrical/electronic
    material in the A+ when I took it back in '00. Because now my (admitted)
    lack of knowledge of these matters is affecting my ability to work quickly,
    and, consequently, my bottom line.

    smackedass, Feb 22, 2007
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