PSU or MOBO failure? - Hardware

This is a discussion on PSU or MOBO failure? - Hardware ; Hello, I have an old machine (self-assembled, with an Asus VP6 mobo dual PIII processors), which is now only used for backup, but is quite useful in that role. It is refusing to boot. No POST, no beeps. The only ...

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  1. PSU or MOBO failure?

    Hello,

    I have an old machine (self-assembled, with an Asus VP6 mobo dual PIII
    processors), which is now only used for backup, but is quite useful in
    that role.

    It is refusing to boot. No POST, no beeps. The only signs of life are :
    (1) the mobo led is lit (2) there is power to the NIC (3) sometimes I get
    a tiny flicker of life on the case power-on led (4) a cpu fan may give one
    or two revolutions then stop.

    Does this sound like PSU failure ? A replacement would be cheap enough to
    risk, but there is obviously no point in bothering at all if someone knows
    that this is far more likely to be the mobo.

    Thanks,

    Geoff

  2. Re: PSU or MOBO failure?

    Geoff writes:

    > Hello,
    >
    > I have an old machine (self-assembled, with an Asus VP6 mobo dual PIII
    > processors), which is now only used for backup, but is quite useful in
    > that role.
    >
    > It is refusing to boot. No POST, no beeps. The only signs of life are :
    > (1) the mobo led is lit (2) there is power to the NIC (3) sometimes I get
    > a tiny flicker of life on the case power-on led (4) a cpu fan may give one
    > or two revolutions then stop.
    >
    > Does this sound like PSU failure ? A replacement would be cheap enough to
    > risk, but there is obviously no point in bothering at all if someone knows
    > that this is far more likely to be the mobo.


    It could be the PSU. To see if this is the case, measure the voltage
    on a hard disk power plug while attempting to power on the machine.
    If you do not get the proper 5V and 12V readings, chances are the PSU
    is broken. To completely rule out the MB, unplug all PSU connections,
    and short pins 13 and 14 (black and green) on the main ATX plug from
    the PSU. This should activate the PSU, and you should be able to
    measure the various voltages.

    --
    Måns Rullgård
    mans@mansr.com

  3. Re: PSU or MOBO failure?

    In article ,
    Måns Rullgård wrote:
    > Geoff writes:
    >
    > > Hello,
    > >
    > > I have an old machine (self-assembled, with an Asus VP6 mobo dual PIII
    > > processors), which is now only used for backup, but is quite useful in
    > > that role.
    > >
    > > It is refusing to boot. No POST, no beeps. The only signs of life are :
    > > (1) the mobo led is lit (2) there is power to the NIC (3) sometimes I get
    > > a tiny flicker of life on the case power-on led (4) a cpu fan may give one
    > > or two revolutions then stop.
    > >
    > > Does this sound like PSU failure ? A replacement would be cheap enough to
    > > risk, but there is obviously no point in bothering at all if someone knows
    > > that this is far more likely to be the mobo.

    >
    > It could be the PSU. To see if this is the case, measure the voltage
    > on a hard disk power plug while attempting to power on the machine.
    > If you do not get the proper 5V and 12V readings, chances are the PSU
    > is broken. To completely rule out the MB, unplug all PSU connections,
    > and short pins 13 and 14 (black and green) on the main ATX plug from
    > the PSU. This should activate the PSU, and you should be able to
    > measure the various voltages.


    What's gotten me a few times is the big 20- or 24-pin connector PS ->
    mobo sometimes looks seated but isn't. No POST but fans are the normal
    symptoms, but I suppose it could be otherwise depending on what's
    contacted. Make sure you hear a click.

    If you buy a replacement PS, do it from a place with a good return
    policy in case that isn't the cause. Newegg is pretty good.
    --
    -eben QebWenE01R@vTerYizUonI.nOetP http://royalty.mine.nu:81
    CANCER: The position of Jupiter says that you should spend the
    rest of the week face down in the mud. Try not to shove a roll of
    duct tape up your nose when taking your driver's test. -- Weird Al

  4. Re: PSU or MOBO failure?

    On Sat, 27 Sep 2008 15:29:26 +0100, Geoff wrote:

    > Hello,
    >
    > I have an old machine (self-assembled, with an Asus VP6 mobo dual PIII
    > processors), which is now only used for backup, but is quite useful in
    > that role.
    >
    > It is refusing to boot. No POST, no beeps. The only signs of life are :
    > (1) the mobo led is lit (2) there is power to the NIC (3) sometimes I get
    > a tiny flicker of life on the case power-on led (4) a cpu fan may give one
    > or two revolutions then stop.
    >
    > Does this sound like PSU failure ? A replacement would be cheap enough to
    > risk, but there is obviously no point in bothering at all if someone knows
    > that this is far more likely to be the mobo.
    >
    > Thanks,
    >
    > Geoff
    >

    I am not sure if any Asus boards had bad capacitors, or not, but many
    motherboards from that generation suffer from bad capacitors. Do you
    notice any bulging or leaking capacitors, especially around the main power
    tap? If it's bad caps, then that may be it for that board unless you can
    find someone who can do the technical soldering that is required.

    --
    Douglas Mayne



  5. Re: PSU or MOBO failure?

    On Sat, 27 Sep 2008 16:11:05 +0100, Måns Rullgård wrote:



    > It could be the PSU. To see if this is the case, measure the voltage on
    > a hard disk power plug while attempting to power on the machine. If you
    > do not get the proper 5V and 12V readings, chances are the PSU is
    > broken. To completely rule out the MB, unplug all PSU connections, and
    > short pins 13 and 14 (black and green) on the main ATX plug from the
    > PSU. This should activate the PSU, and you should be able to measure
    > the various voltages.


    Thank you very much MÃ¥ns,

    I dug out my ageing multimeter and did the HDD power plug test. The
    result is as follows. If I (1) switch off the mains input, (2) switch the
    mains back on (3) power on the machine .. then I get a flicker of power on
    both the 5v an 12v pins ... it is momentary and coincides with one or two
    revolutions of a cpu fan. The machine is then completely dead until I
    cycle the mains input on and off again - powering on the machine without
    cycling the mains in this way has no effect.

    I have not yet shorted pins 13 and 14 .. I am rather at the limit of what
    I understand here and (while I am sure you are giving me good advice), I
    am a little nervous about doing that. I may pluck up courage later.

    Geoff

  6. Re: PSU or MOBO failure?

    On Sat, 27 Sep 2008 13:37:27 -0400, Hactar wrote:



    > What's gotten me a few times is the big 20- or 24-pin connector PS ->
    > mobo sometimes looks seated but isn't. No POST but fans are the normal
    > symptoms, but I suppose it could be otherwise depending on what's
    > contacted. Make sure you hear a click.
    >
    > If you buy a replacement PS, do it from a place with a good return
    > policy in case that isn't the cause. Newegg is pretty good.


    Thanks Hactar,

    You will see that I have responded directly to MÃ¥ns. I have checked that
    the connector is well seated, and it seems to be ok. I am in the UK and
    will pick up a cheap PSU at one of my local stores if that seems to be the
    way ahead. I am lucky in living near to a couple of big distributors. I
    don't know if they will allow me a refund, but I don't mean to spend a lot
    on this box and will just have to take the risk if the PSU does not turn
    out to be the problem.

    Geoff

  7. Re: PSU or MOBO failure?

    On Sat, 27 Sep 2008 15:14:49 -0600, Douglas Mayne wrote:



    > I am not sure if any Asus boards had bad capacitors, or not, but many
    > motherboards from that generation suffer from bad capacitors. Do you
    > notice any bulging or leaking capacitors, especially around the main
    > power tap? If it's bad caps, then that may be it for that board unless
    > you can find someone who can do the technical soldering that is
    > required.


    Thanks Douglas,

    You will see that I have responded directly to MÃ¥ns above. I have had a
    good look at the mobo and can't see any obvious problems. I am guessing
    that result I am seeing may be something to do with capacitance somewhere
    (as if I am getting a small build up of charge when the mains is cycled),
    but I am just surmising and I don't know if it is more likely to be in the
    PSU or on the MOBO.

    Geoff

  8. Re: PSU or MOBO failure?

    In article <1222551365.24930.1@proxy00.news.clara.net>,
    Geoff wrote:
    >
    > You will see that I have responded directly to MÃ¥ns. I have checked that
    > the connector is well seated, and it seems to be ok. I am in the UK and
    > will pick up a cheap PSU at one of my local stores if that seems to be the
    > way ahead. I am lucky in living near to a couple of big distributors. I
    > don't know if they will allow me a refund, but I don't mean to spend a lot
    > on this box and will just have to take the risk if the PSU does not turn
    > out to be the problem.


    Also, my motherboard or PS (one of them) would show the same symptoms if
    there was a short somewhere. Checked that? Bad/loose RAM, card, CPU?

    --
    -eben QebWenE01R@vTerYizUonI.nOetP
    1101000 1110100 1110100 1110000 0111010 0101111 0101111 1110010 1101111
    1111001 1100001 1101100 1110100 1111001 0101110 1101101 1101001 1101110
    1100101 0101110 1101110 1110101 0111010 0111000 0110001 0101111

  9. Re: PSU or MOBO failure?

    On Sat, 27 Sep 2008 22:32:33 +0100, Geoff wrote:



    > I have not yet shorted pins 13 and 14 .. I am rather at the limit of
    > what I understand here and (while I am sure you are giving me good
    > advice), I am a little nervous about doing that. I may pluck up courage
    > later.
    >


    Following up my own post, I shorted the pins. I am seeing a consistent ~
    1.5v on both the 5v and 12v pins. On that basis I will change the PSU
    unless someone tells me I am wrong.

    Thanks again,

    Geoff

  10. Re: PSU or MOBO failure?

    On Sat, 27 Sep 2008 18:35:23 -0400, Hactar wrote:



    > Also, my motherboard or PS (one of them) would show the same symptoms if
    > there was a short somewhere. Checked that? Bad/loose RAM, card, CPU?


    Thanks Hactar,

    As you will see, I followed up my own post to say that I am getting only ~
    1.5v having shorted the pins. I will try a new PSU I think.

    Geoff

  11. Re: PSU or MOBO failure?

    On Sun, 28 Sep 2008 14:02:42 +0100, Geoff rearranged some electrons to
    say:

    > On Sat, 27 Sep 2008 22:32:33 +0100, Geoff wrote:
    >
    >
    >
    >> I have not yet shorted pins 13 and 14 .. I am rather at the limit of
    >> what I understand here and (while I am sure you are giving me good
    >> advice), I am a little nervous about doing that. I may pluck up courage
    >> later.
    >>
    >>

    > Following up my own post, I shorted the pins. I am seeing a consistent
    > ~ 1.5v on both the 5v and 12v pins. On that basis I will change the PSU
    > unless someone tells me I am wrong.
    >
    > Thanks again,
    >
    > Geoff


    Most power supplies need some minimum load on them to operate. Make sure
    you have something on it (like an old disk drive) that can provide a load
    when you do the test.

  12. Re: PSU or MOBO failure?

    On Sun, 28 Sep 2008 18:11:54 +0200, david wrote:

    < snip >
    >
    > Most power supplies need some minimum load on them to operate. Make
    > sure you have something on it (like an old disk drive) that can provide
    > a load when you do the test.


    Thank-you David,

    Since the PSU is still in the machine, I repeated the test with the
    existing HDD as load (with and without the ribbon cable attached). I
    repeated with an old HDD too. Same result as before.

    Geoff

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