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[SOLVED] Unusual drive failure - 12v line short

 
 
Mike Tomlinson
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      Jun 7th, 09, 4:17 PM

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


 
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Rod Speed
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      Jun 7th, 09, 7:47 PM
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.


 
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Clint Sharp
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      Jun 7th, 09, 7:49 PM
In message <W_QWl.57448$(E-Mail Removed)2>, Ato_Zee
<(E-Mail Removed)> 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
 
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Jerry Peters
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      Jun 7th, 09, 9:50 PM
In comp.sys.ibm.pc.hardware.storage Ato_Zee <(E-Mail Removed)> 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
 
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Franc Zabkar
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      Jun 7th, 09, 11:36 PM
On Sun, 7 Jun 2009 16:17:44 +0100, Mike Tomlinson <(E-Mail Removed)>
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
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Please remove one 'i' from my address when replying by email.
 
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Robert Nichols
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      Jun 8th, 09, 12:31 AM
In article <(E-Mail Removed)>,
Gerald Abrahamson <(E-Mail Removed)> 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"
 
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Arno
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      Jun 8th, 09, 1:18 AM
In comp.sys.ibm.pc.hardware.storage Gerald Abrahamson <(E-Mail Removed)> wrote:
> On Sun, 7 Jun 2009 16:17:44 +0100, Mike Tomlinson
> <(E-Mail Removed)> 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
 
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Mike Tomlinson
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      Jun 8th, 09, 6:19 AM
In article <(E-Mail Removed)>, Franc Zabkar
<(E-Mail Removed)> 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


 
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Bob Willard
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      Jun 8th, 09, 12:17 PM
Robert Nichols wrote:
> In article <(E-Mail Removed)>,
> Gerald Abrahamson <(E-Mail Removed)> 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
 
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Mike Tomlinson
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      Jun 8th, 09, 7:09 PM
In article <U4$(E-Mail Removed)>, Clint Sharp
<(E-Mail Removed)> 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


 
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