PC re-boots on its own.

Discussion in 'Computer Support' started by ian field, Apr 28, 2010.

  1. ian field

    ian field Guest

    Every now and then my PC re-boots, most often about half an hour after
    powering up but can happen any time.

    Is this a symptom of failing electrolytic capacitors?

    And is it easy to tell wether the PSU or MOBO is prime suspect?

    TIA.

    PS: there's always a click from the scan mode select relay in the monitor
    just as the screen goes blank - in case that means anything to anyone.
     
    ian field, Apr 28, 2010
    #1
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  2. ian field

    Mike Easter Guest

    ian field wrote:
    > Every now and then my PC re-boots, most often about half an hour after
    > powering up but can happen any time.
    >
    > Is this a symptom of failing electrolytic capacitors?


    IMO some kind of hardware problem; capacitors, PS, heat. I lean toward
    PS for some reason.

    > And is it easy to tell wether the PSU or MOBO is prime suspect?


    No.

    > PS: there's always a click from the scan mode select relay in the monitor
    > just as the screen goes blank - in case that means anything to anyone.


    I suppose something (the unknown problem condition) is causing the mobo
    to 'shut down' and that shut down causes a loss of video and that loss
    of vid signal is where the monitor click is coming from.

    I like the newsgroup alt.comp.hardware.pc-homebuilt for this kind of
    problem.


    --
    Mike Easter
     
    Mike Easter, Apr 28, 2010
    #2
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  3. ian field

    ian field Guest

    "Mike Easter" <> wrote in message
    news:...
    > ian field wrote:
    >> Every now and then my PC re-boots, most often about half an hour after
    >> powering up but can happen any time.
    >>
    >> Is this a symptom of failing electrolytic capacitors?

    >
    > IMO some kind of hardware problem; capacitors, PS, heat. I lean toward
    > PS for some reason.
    >
    >> And is it easy to tell wether the PSU or MOBO is prime suspect?

    >
    > No.
    >
    >> PS: there's always a click from the scan mode select relay in the monitor
    >> just as the screen goes blank - in case that means anything to anyone.

    >
    > I suppose something (the unknown problem condition) is causing the mobo to
    > 'shut down' and that shut down causes a loss of video and that loss of vid
    > signal is where the monitor click is coming from.


    Most monitors have a bank of capacitors to tune the deflection coil
    inductance for the various scan frequencies, usually about 3 of these are
    switched by power MOSFETs, but on larger monitors 1 or 2 more capacitors are
    switched by relays.

    It occurred to me that hearing one of the relays click at the instant the
    monitor blanks out might be a significant symptom.

    >
    > I like the newsgroup alt.comp.hardware.pc-homebuilt for this kind of
    > problem.



    I'll give it a try.

    Thanks.
     
    ian field, Apr 28, 2010
    #3
  4. ian field

    Jordon Guest

    Mike Easter wrote:
    > ian field wrote:
    >> Every now and then my PC re-boots, most often about half an hour after
    >> powering up but can happen any time.
    >>
    >> Is this a symptom of failing electrolytic capacitors?


    > IMO some kind of hardware problem; capacitors, PS, heat. I lean toward
    > PS for some reason.


    And if it's heat there are freeware programs that will
    tell you the CPU temp and CPU fan speed (if there are
    sensors). And most every computer made in the last 5
    years has sensors.

    Every time I've had intermittent shutdowns, that's the
    first place I look.

    --
    Jordon
     
    Jordon, Apr 28, 2010
    #4
  5. ian field

    ian field Guest

    "Jordon" <jordon@REMOVE~THISmyrealbox.com> wrote in message
    news:hraaii$lm1$-september.org...
    > Mike Easter wrote:
    >> ian field wrote:
    >>> Every now and then my PC re-boots, most often about half an hour after
    >>> powering up but can happen any time.
    >>>
    >>> Is this a symptom of failing electrolytic capacitors?

    >
    >> IMO some kind of hardware problem; capacitors, PS, heat. I lean toward
    >> PS for some reason.

    >
    > And if it's heat there are freeware programs that will
    > tell you the CPU temp and CPU fan speed (if there are
    > sensors). And most every computer made in the last 5
    > years has sensors.
    >
    > Every time I've had intermittent shutdowns, that's the
    > first place I look.


    I'm guessing there would be tools/utils on the MOBO driver disk if there
    were sensors.
     
    ian field, Apr 28, 2010
    #5
  6. ian field

    Mike Easter Guest

    ian field wrote:
    > "Jordon"


    >> And if it's heat there are freeware programs that will
    >> tell you the CPU temp and CPU fan speed (if there are
    >> sensors). And most every computer made in the last 5
    >> years has sensors.
    >>
    >> Every time I've had intermittent shutdowns, that's the
    >> first place I look.

    >
    > I'm guessing there would be tools/utils on the MOBO driver disk if there
    > were sensors.


    I would look in the mobo manual or get some info from the mobo setup.

    Some mobo/s have sensors but no utilities on the disk.


    --
    Mike Easter
     
    Mike Easter, Apr 28, 2010
    #6
  7. ian field

    chuckcar Guest

    "ian field" <> wrote in
    news:CZ1Cn.51851$2:

    >
    > "Mike Easter" <> wrote in message
    > news:...


    > It occurred to me that hearing one of the relays click at the instant
    > the monitor blanks out might be a significant symptom.
    >

    No, just the monitor switching when the computer starts. Happens
    every boot, but you're not listening for it is all. It no longer
    gets a video signal so it switches. AT the exact mement the power light
    goes amber you'll notice.



    --
    (setq (chuck nil) car(chuck) )
     
    chuckcar, Apr 29, 2010
    #7
  8. ian field

    Desk Rabbit Guest

    On 28/04/2010 22:03, ian field wrote:
    > Every now and then my PC re-boots, most often about half an hour after
    > powering up but can happen any time.
    >
    > Is this a symptom of failing electrolytic capacitors?
    >
    > And is it easy to tell wether the PSU or MOBO is prime suspect?


    Yes, replace one with a known good part. PSU is the cheapest and easiest
    but any good computer repair shop should be able to help.
     
    Desk Rabbit, Apr 29, 2010
    #8
  9. ian field

    Whiskers Guest

    On 2010-04-28, ian field <> wrote:
    > Every now and then my PC re-boots, most often about half an hour after
    > powering up but can happen any time.


    [...]

    Start by eliminating the simplest and cheapest possibility - overheating.
    Use the 'canned air' sold for the purpose in electronics shops to blow out
    all the dust and fluff from the fans, ducts, vents, and heat sinks - not
    forgetting the power supply if this is a desktop or 'tower' machine.

    Check that all the fans are spinning freely and actually do start when the
    computer starts. If not, make sure the fan wires are all securely
    connected. Fans are usually cheap to replace, and not too fiddly for most
    people - but do take care to avoid static discharges between your body and
    the computer while you are working inside it.

    All this being done with the power unplugged and the casing open, of
    course.

    Expect a /lot/ of dust!

    --
    -- ^^^^^^^^^^
    -- Whiskers
    -- ~~~~~~~~~~
     
    Whiskers, Apr 29, 2010
    #9
  10. ian field

    ian field Guest

    "Whiskers" <> wrote in message
    news:...
    > On 2010-04-28, ian field <> wrote:
    >> Every now and then my PC re-boots, most often about half an hour after
    >> powering up but can happen any time.

    >
    > [...]
    >
    > Start by eliminating the simplest and cheapest possibility - overheating.
    > Use the 'canned air' sold for the purpose in electronics shops to blow out
    > all the dust and fluff from the fans, ducts, vents, and heat sinks - not
    > forgetting the power supply if this is a desktop or 'tower' machine.
    >
    > Check that all the fans are spinning freely and actually do start when the
    > computer starts. If not, make sure the fan wires are all securely
    > connected. Fans are usually cheap to replace, and not too fiddly for most
    > people - but do take care to avoid static discharges between your body and
    > the computer while you are working inside it.
    >
    > All this being done with the power unplugged and the casing open, of
    > course.
    >
    > Expect a /lot/ of dust!


    The side is permanently off so I can see/hear the fans are going. Recently I
    put in an extra USB card and cleaned out all the crap while I was at it.

    Before you blame the USB card, it was doing it before I added that.
     
    ian field, Apr 29, 2010
    #10
  11. ian field

    Desk Rabbit Guest

    On 29/04/2010 15:50, ian field wrote:
    > "Whiskers"<> wrote in message
    > news:...
    >> On 2010-04-28, ian field<> wrote:
    >>> Every now and then my PC re-boots, most often about half an hour after
    >>> powering up but can happen any time.

    >>
    >> [...]
    >>
    >> Start by eliminating the simplest and cheapest possibility - overheating.
    >> Use the 'canned air' sold for the purpose in electronics shops to blow out
    >> all the dust and fluff from the fans, ducts, vents, and heat sinks - not
    >> forgetting the power supply if this is a desktop or 'tower' machine.
    >>
    >> Check that all the fans are spinning freely and actually do start when the
    >> computer starts. If not, make sure the fan wires are all securely
    >> connected. Fans are usually cheap to replace, and not too fiddly for most
    >> people - but do take care to avoid static discharges between your body and
    >> the computer while you are working inside it.
    >>
    >> All this being done with the power unplugged and the casing open, of
    >> course.
    >>
    >> Expect a /lot/ of dust!

    >
    > The side is permanently off so I can see/hear the fans are going.


    Bad idea. The air will not flow through the case with the side off so
    you have made things worse.
     
    Desk Rabbit, Apr 30, 2010
    #11
  12. ian field

    Desk Rabbit Guest

    On 28/04/2010 22:42, ian field wrote:
    > "Mike Easter"<> wrote in message
    > news:...
    >> ian field wrote:
    >>> Every now and then my PC re-boots, most often about half an hour after
    >>> powering up but can happen any time.
    >>>
    >>> Is this a symptom of failing electrolytic capacitors?

    >>
    >> IMO some kind of hardware problem; capacitors, PS, heat. I lean toward
    >> PS for some reason.
    >>
    >>> And is it easy to tell wether the PSU or MOBO is prime suspect?

    >>
    >> No.
    >>
    >>> PS: there's always a click from the scan mode select relay in the monitor
    >>> just as the screen goes blank - in case that means anything to anyone.

    >>
    >> I suppose something (the unknown problem condition) is causing the mobo to
    >> 'shut down' and that shut down causes a loss of video and that loss of vid
    >> signal is where the monitor click is coming from.

    >
    > Most monitors have a bank of capacitors to tune the deflection coil
    > inductance for the various scan frequencies, usually about 3 of these are
    > switched by power MOSFETs, but on larger monitors 1 or 2 more capacitors are
    > switched by relays.
    >
    > It occurred to me that hearing one of the relays click at the instant the
    > monitor blanks out might be a significant symptom.

    Red herring.

    Just try unplugging the signal cable when it is running normally. Bet
    you hear a click.
     
    Desk Rabbit, Apr 30, 2010
    #12
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