Power problem

Discussion in 'Computer Information' started by Mastertone, Jun 3, 2007.

  1. Mastertone

    Mastertone Guest

    Oh-oh, before I blow somrthing...I turn on the power and I get power
    to everything for a split second and then poof. I see power to my
    video card and then it goes right off. I do have power to my power
    supply because the fan is on, but the case fan is not. What did I do?
    :-(

    Thx
     
    Mastertone, Jun 3, 2007
    #1
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  2. Mastertone

    babaloo Guest

    I hope for your sake your problem is merely a failed power supply. This is
    likely the situation if no power is getting out to the hard drives (do you
    hear/feel them spinning?) or motherboard after the initial swith flip.
    Power supplies fail regularly, particularly the cheapo ones that come with
    cases.
    If your CPU is not properly cooled and has fried (or failed for any reason)
    that could explain what you see.
    I would suggest that you not turn on the computer again and take it to be
    serviced if you are not familiar with how to do this yourself.
    It is not clear if the motherboard is fried. The likelihood of frying the
    motherboard (as well as everything else in your computer) is real if an
    unstable power supply sends out an uncontrolled jolt when you turn it on.
     
    babaloo, Jun 3, 2007
    #2
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  3. Mastertone

    Mastertone Guest

    The PS is a 600W Noisetaker.

    If the video card gets power for a split second, does that mean my
    MOBO is okay and my CPU is fried? How do you test all of these?

    Thx

    On Sun, 3 Jun 2007 10:31:46 -0700, "babaloo" <>
    wrote:

    >I hope for your sake your problem is merely a failed power supply. This is
    >likely the situation if no power is getting out to the hard drives (do you
    >hear/feel them spinning?) or motherboard after the initial swith flip.
    >Power supplies fail regularly, particularly the cheapo ones that come with
    >cases.
    >If your CPU is not properly cooled and has fried (or failed for any reason)
    >that could explain what you see.
    >I would suggest that you not turn on the computer again and take it to be
    >serviced if you are not familiar with how to do this yourself.
    >It is not clear if the motherboard is fried. The likelihood of frying the
    >motherboard (as well as everything else in your computer) is real if an
    >unstable power supply sends out an uncontrolled jolt when you turn it on.
    >
     
    Mastertone, Jun 3, 2007
    #3
  4. Mastertone

    Paul Guest

    Mastertone wrote:
    > The PS is a 600W Noisetaker.
    >
    > If the video card gets power for a split second, does that mean my
    > MOBO is okay and my CPU is fried? How do you test all of these?
    >
    > Thx


    On my last couple of builds, I've put all the components on a table
    top and not into the case. You can place the motherboard on top of a
    thick telephone book (one with a cardboard cover). That will leave
    room for the video card faceplate tab to hang down. Be careful with
    doing this, because if you assemble the system on a table, the
    plug-in cards are not secured. One tug on an I/O cable, and a card
    could be pulled from its slot.

    It could be that something is shorting. And removing stuff from the
    case, and adding components one at a time, and testing the response,
    may tell you what is wrong. For example, with a CPU and heatsink and
    cooler installed, but no RAM or video card, the computer case speaker
    should beep the "missing RAM" code. After you install the RAM, if
    the RAM is OK, you'd hear the "missing Video card" code. You can
    do tests like that, and see how much stuff you can add, before it
    "falls over" again.

    Always switch off the supply while adding or removing components.
    And if building the system on a table top, verify the video
    card is properly seated, before each power "switch-on" attempt.

    Paul

    >
    > On Sun, 3 Jun 2007 10:31:46 -0700, "babaloo" <>
    > wrote:
    >
    >> I hope for your sake your problem is merely a failed power supply. This is
    >> likely the situation if no power is getting out to the hard drives (do you
    >> hear/feel them spinning?) or motherboard after the initial swith flip.
    >> Power supplies fail regularly, particularly the cheapo ones that come with
    >> cases.
    >> If your CPU is not properly cooled and has fried (or failed for any reason)
    >> that could explain what you see.
    >> I would suggest that you not turn on the computer again and take it to be
    >> serviced if you are not familiar with how to do this yourself.
    >> It is not clear if the motherboard is fried. The likelihood of frying the
    >> motherboard (as well as everything else in your computer) is real if an
    >> unstable power supply sends out an uncontrolled jolt when you turn it on.
    >>
     
    Paul, Jun 3, 2007
    #4
  5. Mastertone

    Mastertone Guest

    On Sun, 03 Jun 2007 17:25:32 -0400, Paul <> wrote:

    Thx, I'll try it out....appreciate the feedback
     
    Mastertone, Jun 3, 2007
    #5
  6. Mastertone

    w_tom Guest

    On Jun 3, 6:49 pm, Mastertone <> wrote:
    > Thx, I'll try it out....appreciate the feedback


    The damage that blew out a video controller had already occured long
    before a visual indication was observed. If the power supply has
    essential functions, then supply must not harm other computer
    components. Damage would be due to something else.

    If a fan spins, then maybe -12 volts is working; but not 3.3, 5, or
    +12. A spinning fan reports nothing useful.

    Expressions such as "It could be that .." are speculation. To fix
    something, definitive answers are required. That means numbers from a
    3.5 digit multimeter. Voltages can even be defective and still a
    computer boots, lights glow, or disk drive spins. Numbers and two
    minutes to obtain definitive answers is in "When your computer dies
    without warning....." starting 6 Feb 2007 in the newsgroup
    alt.windows-xp at:
    http://tinyurl.com/yvf9vh

    Once that 'system' (yes a system; not just a power supply) is
    confirmed, then move on to other suspects. Video controller may have
    been defective. Or maybe motherboard is shorted. Solution starts by
    breaking that problem down into parts; then analyzing those part.
    First two minutes get numbers from the meter. Numbers that can also
    result in useful replies here.
     
    w_tom, Jun 4, 2007
    #6
  7. Mastertone

    Mastertone Guest

    Before I rip everything out, why does the power supply come on for a
    split second every time I turn it off and back on? I turn on power
    and nothing, I unplug the power supply and plug it back in, and WHAM,
    I get a short supply. Does this indicate anything? Thx again :)
     
    Mastertone, Jun 6, 2007
    #7
  8. Mastertone

    Mastertone Guest

    Ah HAH!!!!

    Looks like it's the cheap case power on switch!
     
    Mastertone, Jun 6, 2007
    #8
  9. Mastertone

    Paul Guest

    Mastertone wrote:
    > Before I rip everything out, why does the power supply come on for a
    > split second every time I turn it off and back on? I turn on power
    > and nothing, I unplug the power supply and plug it back in, and WHAM,
    > I get a short supply. Does this indicate anything? Thx again :)


    For the power supply to come on:

    1) It needs 35 milliseconds or so (a typical number for some switching
    regulators), for the +5VSB and any internal supervisor voltages to
    stabilize. The supervisor voltage is needed so the power supply can
    start looking at PS_ON#.

    2) The power supply is soft-switched, via PS_ON#. When PS_ON# is pulled
    to ground, the power supply starts. When left to float, a pullup
    resistor in the power supply, is supposed to pull the signal to the
    inactive state.

    Something is making the PS_ON# signal active for a short period of time.
    It is probably not the motherboard. So this could be a defect with the
    PSU.

    Once you have disassembled the thing, you can test the PSU while it is
    not connected to anything. If you flip the switch on the back of the
    PSU, and it starts for a second, then that would be a PSU problem.

    If you want to test the PSU, some people claim you should connect a
    dummy load. A couple old disk drives (ones you no longer care about),
    connected to the PSU by themselves, might draw a couple amps, and
    provide some loading. (I have a home built "load box" that draws
    current from each rail, and that is what I use.)

    (A old article I wrote, about building a load box...)
    http://groups.google.ca/group/alt.comp.periphs.mainboard.asus/msg/19647caf2c65504b?dmode=source

    To test a PSU by itself, you connect PS_ON# to an adjacent COM pin.
    These two documents, show the wiring for 20 pin and 24 pin power
    supplies. PS_ON# is green and COM (on either side of PS_ON#) is
    black. A paper clip can be used as a short term connection between
    the two adjacent pins. That should cause the PSU fan to spin.

    http://www.formfactors.org/developer/specs/atx/ATX12V_1_3dg.pdf
    http://www.formfactors.org/developer/specs/ATX12V_PSDG_2_2_public_br2.pdf

    Paul
     
    Paul, Jun 6, 2007
    #9
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