Unusual drive failure - 12v line short

Discussion in 'DIY Computers' started by Mike Tomlinson, Jun 7, 2009.

  1. I have a PVR thingywotsit on my TV. Today it died, no power. Listen to
    PSU - tick, tick, tick. Ah, thought I, bad caps.

    But no, the cause was the hard disk - the 12v line was completely short.
    I've not seen this mode of failure of a hard drive before now; has
    anyone else?

    Western Digital model WDC2500BB-00RDA0, 250GB.
    date on drive: 25 Jul 07, out of warranty

    Stuck in a 160GB IBM from my bits box and off we went.

    It may be relevant that the drive is on 24/7. I cannot find any specs
    for expected longevity or MTBF on wdc.com.

    --
    (\__/)
    (='.'=) Bunny says Windows 7 is Vi$ta reloaded.
    (")_(") http://imgs.xkcd.com/comics/windows_7.png
     
    Mike Tomlinson, Jun 7, 2009
    #1
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  2. Mike Tomlinson

    Rod Speed Guest

    Mike Tomlinson wrote:

    > I have a PVR thingywotsit on my TV. Today it died, no power.
    > Listen to PSU - tick, tick, tick. Ah, thought I, bad caps.


    > But no, the cause was the hard disk - the 12v line was
    > completely short. I've not seen this mode of failure of
    > a hard drive before now; has anyone else?


    Yes, usually due to a capacitor across that rail as a filter shorting.

    Not common, but not unheard of.

    > Western Digital model WDC2500BB-00RDA0, 250GB.
    > date on drive: 25 Jul 07, out of warranty


    > Stuck in a 160GB IBM from my bits box and off we went.


    > It may be relevant that the drive is on 24/7.


    Nope. They get used like that a lot.

    > I cannot find any specs for expected longevity or MTBF on wdc.com.


    The specs are pretty sparse on there now but they are typically 250K hours on consumer drives like that.
     
    Rod Speed, Jun 7, 2009
    #2
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  3. Mike Tomlinson

    Clint Sharp Guest

    In message <W_QWl.57448$2>, Ato_Zee
    <> writes
    >
    >> But no, the cause was the hard disk - the 12v line was completely short.
    >> I've not seen this mode of failure of a hard drive before now; has
    >> anyone else?

    >
    >Maybe a capacitor across the 12V line died. RIP.

    More likely to be a transorb but most likely to be the motor driver IC.
    --
    Clint Sharp
     
    Clint Sharp, Jun 7, 2009
    #3
  4. Mike Tomlinson

    Jerry Peters Guest

    In comp.sys.ibm.pc.hardware.storage Ato_Zee <> wrote:
    >
    >> But no, the cause was the hard disk - the 12v line was completely short.
    >> I've not seen this mode of failure of a hard drive before now; has
    >> anyone else?

    >
    > Maybe a capacitor across the 12V line died. RIP.


    Had a Dell laptop with that problem; capacitor across the 19vdc power
    input shorted, so capacitors do fail that way.

    Jerry
     
    Jerry Peters, Jun 7, 2009
    #4
  5. Mike Tomlinson

    Franc Zabkar Guest

    On Sun, 7 Jun 2009 16:17:44 +0100, Mike Tomlinson <>
    put finger to keyboard and composed:

    >I have a PVR thingywotsit on my TV. Today it died, no power. Listen to
    >PSU - tick, tick, tick. Ah, thought I, bad caps.
    >
    >But no, the cause was the hard disk - the 12v line was completely short.
    >I've not seen this mode of failure of a hard drive before now; has
    >anyone else?


    It's common enough. There will probably be two TVS (transient voltage
    suppression) diodes, one across the +5V rail, the other across the
    +12V. You can remove the shorted diode and the drive should work
    without it. Just make sure your power supply is good ...

    - Franc Zabkar
    --
    Please remove one 'i' from my address when replying by email.
     
    Franc Zabkar, Jun 7, 2009
    #5
  6. In article <>,
    Gerald Abrahamson <> wrote:
    :
    :Most modern drives (within last 5 years or so) have a very
    :long expected lifetime (MTBF = 250,000 hrs = 28 years
    :running 24/7, and 500+k hours is more typical today).

    The units for MTBF are not hours but device-hours, i.e., the product of
    the number of hours and the number of devices being observed, and that
    rating applies only during the device's rated service life, which is an
    entirely separate parameter.

    MTBF of 250,000 is almost totally unrelated to the expected service
    life. It is quite possible to have a device with its MTBF 250,000 and a
    rated service life of 1 hour. It just means that if you ran 250,000 of
    those devices for one hour you should expect 1 failure. Once a device
    passes its rated service life, the MTBF rating no longer applies.
    Think: a battery used to provide power to a missle's guidance system --
    built to be highly reliable for the short time it's needed, and pretty
    much assured to go dead not long after that. High MTBF, short service
    life.

    Looking at the power-on hours and corresponding normalized SMART value
    on a few fairly recent drives, it appears that the SMART warning due to
    power-on hours would come at about 10 years of power on.

    --
    Bob Nichols AT comcast.net I am "RNichols42"
     
    Robert Nichols, Jun 8, 2009
    #6
  7. Mike Tomlinson

    Arno Guest

    In comp.sys.ibm.pc.hardware.storage Gerald Abrahamson <> wrote:
    > On Sun, 7 Jun 2009 16:17:44 +0100, Mike Tomlinson
    > <> wrote:


    >>
    >>I have a PVR thingywotsit on my TV. Today it died, no power. Listen to
    >>PSU - tick, tick, tick. Ah, thought I, bad caps.
    >>
    >>But no, the cause was the hard disk - the 12v line was completely short.
    >>I've not seen this mode of failure of a hard drive before now; has
    >>anyone else?
    >>
    >>Western Digital model WDC2500BB-00RDA0, 250GB.
    >>date on drive: 25 Jul 07, out of warranty
    >>
    >>Stuck in a 160GB IBM from my bits box and off we went.
    >>
    >>It may be relevant that the drive is on 24/7. I cannot find any specs
    >>for expected longevity or MTBF on wdc.com.


    > Most modern drives (within last 5 years or so) have a very
    > long expected lifetime (MTBF = 250,000 hrs = 28 years
    > running 24/7, and 500+k hours is more typical today).


    The MTFB is completely untelated to the device lifetime.
    It just describes the failure probablility during the device
    lifetime. Device lifetime is stated in the device datasheet
    and typically 5 years.

    For example, an MTBF of 250'000h gives you a failure
    probability of 365*24/250'000 = 3.5%/year, in the first
    5 years. It dioes not make any statement about the failure
    pobability afterwards.

    Arno
     
    Arno, Jun 8, 2009
    #7
  8. In article <>, Franc Zabkar
    <> writes

    >It's common enough. There will probably be two TVS (transient voltage
    >suppression) diodes, one across the +5V rail, the other across the
    >+12V.


    You're right. I took the board off and there is a SMT diode on the
    hidden side across the 12v line, and it is reading a short. I suppose
    it could be the motor controller chip that's shorted, but it looks
    intact.

    >You can remove the shorted diode and the drive should work
    >without it. Just make sure your power supply is good ...


    I'll take the board into work, remove the diode today and report back.
    Thanks. 250gb is still a useful capacity to have. The drive's in a
    personal video recorder, not a PC, and this PVR is known to have a weak
    PSU.

    --
    (\__/)
    (='.'=) Bunny says Windows 7 is Vi$ta reloaded.
    (")_(") http://imgs.xkcd.com/comics/windows_7.png
     
    Mike Tomlinson, Jun 8, 2009
    #8
  9. Mike Tomlinson

    Bob Willard Guest

    Robert Nichols wrote:
    > In article <>,
    > Gerald Abrahamson <> wrote:
    > :
    > :Most modern drives (within last 5 years or so) have a very
    > :long expected lifetime (MTBF = 250,000 hrs = 28 years
    > :running 24/7, and 500+k hours is more typical today).
    >
    > The units for MTBF are not hours but device-hours, i.e., the product of
    > the number of hours and the number of devices being observed, and that
    > rating applies only during the device's rated service life, which is an
    > entirely separate parameter.
    >
    > MTBF of 250,000 is almost totally unrelated to the expected service
    > life. It is quite possible to have a device with its MTBF 250,000 and a
    > rated service life of 1 hour. It just means that if you ran 250,000 of
    > those devices for one hour you should expect 1 failure. Once a device
    > passes its rated service life, the MTBF rating no longer applies.
    > Think: a battery used to provide power to a missle's guidance system --
    > built to be highly reliable for the short time it's needed, and pretty
    > much assured to go dead not long after that. High MTBF, short service
    > life.
    >
    > Looking at the power-on hours and corresponding normalized SMART value
    > on a few fairly recent drives, it appears that the SMART warning due to
    > power-on hours would come at about 10 years of power on.
    >


    That is total BS. MTBF is per device. Read, for example, MIL-HDBK-217.
    --
    Cheers, Bob
     
    Bob Willard, Jun 8, 2009
    #9
  10. In article <U4$>, Clint Sharp
    <> writes

    >More likely to be a transorb but most likely to be the motor driver IC.


    They usually burn up when they fail, and this one looked fine. Took out
    the shorted diode and the drive span up ok. Not yet tried it.

    --
    (\__/)
    (='.'=) Bunny says Windows 7 is Vi$ta reloaded.
    (")_(") http://imgs.xkcd.com/comics/windows_7.png
     
    Mike Tomlinson, Jun 8, 2009
    #10
  11. In article <W$>, Mike Tomlinson
    <> writes

    >I'll take the board into work, remove the diode today and report back.


    Took out the shorted diode today and the drive span up OK on a PC power
    supply. Not yet tried it in the PVR but am sure it will be OK.

    Thanks everyone for your suggestions.

    --
    (\__/)
    (='.'=) Bunny says Windows 7 is Vi$ta reloaded.
    (")_(") http://imgs.xkcd.com/comics/windows_7.png
     
    Mike Tomlinson, Jun 8, 2009
    #11
  12. In article <h0is0c$8ga$-september.org>,
    Bob Willard <> wrote:
    :Robert Nichols wrote:
    :> In article <>,
    :> Gerald Abrahamson <> wrote:
    :> :
    :> :Most modern drives (within last 5 years or so) have a very
    :> :long expected lifetime (MTBF = 250,000 hrs = 28 years
    :> :running 24/7, and 500+k hours is more typical today).
    :>
    :> The units for MTBF are not hours but device-hours, i.e., the product of
    :> the number of hours and the number of devices being observed, and that
    :> rating applies only during the device's rated service life, which is an
    :> entirely separate parameter.
    :>
    :> MTBF of 250,000 is almost totally unrelated to the expected service
    :> life. It is quite possible to have a device with its MTBF 250,000 and a
    :> rated service life of 1 hour. It just means that if you ran 250,000 of
    :> those devices for one hour you should expect 1 failure. Once a device
    :> passes its rated service life, the MTBF rating no longer applies.
    :> Think: a battery used to provide power to a missle's guidance system --
    :> built to be highly reliable for the short time it's needed, and pretty
    :> much assured to go dead not long after that. High MTBF, short service
    :> life.
    :>
    :> Looking at the power-on hours and corresponding normalized SMART value
    :> on a few fairly recent drives, it appears that the SMART warning due to
    :> power-on hours would come at about 10 years of power on.
    :>
    :
    :That is total BS. MTBF is per device. Read, for example, MIL-HDBK-217.

    In a brief perusal of that document (scanned copy -- no search function
    available) I do not find the term "MTBF" mentioned anywhere, so I fail
    to see why you would consider that document the definitive work on the
    subject.

    OTOH, I spent 26 years designing high-reliability electrical and
    electronic equipment and do have some idea of what I am talking about.

    --
    Bob Nichols AT comcast.net I am "RNichols42"
     
    Robert Nichols, Jun 9, 2009
    #12
  13. Mike Tomlinson

    Arno Guest

    In comp.sys.ibm.pc.hardware.storage Robert Nichols <> wrote:
    > In article <h0is0c$8ga$-september.org>,
    > Bob Willard <> wrote:
    > :Robert Nichols wrote:
    > :> In article <>,
    > :> Gerald Abrahamson <> wrote:
    > :> :
    > :> :Most modern drives (within last 5 years or so) have a very
    > :> :long expected lifetime (MTBF = 250,000 hrs = 28 years
    > :> :running 24/7, and 500+k hours is more typical today).
    > :>
    > :> The units for MTBF are not hours but device-hours, i.e., the product of
    > :> the number of hours and the number of devices being observed, and that
    > :> rating applies only during the device's rated service life, which is an
    > :> entirely separate parameter.
    > :>
    > :> MTBF of 250,000 is almost totally unrelated to the expected service
    > :> life. It is quite possible to have a device with its MTBF 250,000 and a
    > :> rated service life of 1 hour. It just means that if you ran 250,000 of
    > :> those devices for one hour you should expect 1 failure. Once a device
    > :> passes its rated service life, the MTBF rating no longer applies.
    > :> Think: a battery used to provide power to a missle's guidance system --
    > :> built to be highly reliable for the short time it's needed, and pretty
    > :> much assured to go dead not long after that. High MTBF, short service
    > :> life.
    > :>
    > :> Looking at the power-on hours and corresponding normalized SMART value
    > :> on a few fairly recent drives, it appears that the SMART warning due to
    > :> power-on hours would come at about 10 years of power on.
    > :>
    > :
    > :That is total BS. MTBF is per device. Read, for example, MIL-HDBK-217.


    > In a brief perusal of that document (scanned copy -- no search function
    > available) I do not find the term "MTBF" mentioned anywhere, so I fail
    > to see why you would consider that document the definitive work on the
    > subject.


    > OTOH, I spent 26 years designing high-reliability electrical and
    > electronic equipment and do have some idea of what I am talking about.


    No need to sling documents around. Even the name says it is
    a failure probability per time, not a life time. Probabilities
    are not individual counters and so a "per device" does not apply,
    given statistical independence. This also means that the probability
    of a device failing is not dependent on the non-failing time it
    had before. (Here the "component life" comes in. It limits that
    independence to a maximum non-failing operating time and says the
    MTBF may become invalid what that is exceeded.)

    When you actually want to measure MTBF, you run a number of devices
    for a time until all have failed or the component life has
    been exceeded (the latter usually done by statistical models
    and/or accellerated ageing), count all non-failing hour you got
    and divide them by the device number.

    Now, this may be the wrong approach. It is quite possible that
    device failure probability is not independent on the previous
    non-failing operating time. In that case, one MTBF would not be the
    right measure. Several different MTBFs could be given for
    different periods of a devices lifetime so far as an approximation.
    But this is not how it is done at this time. At this time
    you get a failure probability per operating hour and the
    only history of the device that goes into it is whether it
    has already failed (and then all bets are off, it is assumed
    to stay failed by the model) or whether it has exceeded its
    component life time and the MTBF stated simply does
    not apply anymore and is not replaced by any other value
    instead.

    Arno
     
    Arno, Jun 9, 2009
    #13
  14. Mike Tomlinson

    Eric Gisin Guest

    "Mike Tomlinson" <> wrote in message news:...
    > In article <W$>, Mike Tomlinson
    > <> writes
    >
    >>I'll take the board into work, remove the diode today and report back.

    >
    > Took out the shorted diode today and the drive span up OK on a PC power
    > supply. Not yet tried it in the PVR but am sure it will be OK.
    >
    > Thanks everyone for your suggestions.
    >

    PVR may have a crappy PSU with poor 12V regulation.
     
    Eric Gisin, Jun 11, 2009
    #14
  15. Mike Tomlinson

    Barry OGrady Guest

    I had a CPM computer whose 10MB HD would not spin up.
    Fortunately the power supply had LEDs to show power and
    the 12v LED was off. It turned out to be a shorted capacitor.

    Barry
    =====
    Home page
    http://members.iinet.net.au/~barry.og
     
    Barry OGrady, Jun 17, 2009
    #15
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