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#11
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Unusual drive failure - 12v line short
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$ta reloaded. (")_(") http://imgs.xkcd.com/comics/windows_7.png |
#12
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Unusual drive failure - 12v line short
Robert Nichols wrote:
In article , Gerald Abrahamson wrote: : :Most modern drives (within last 5 years or so) have a very :long expected lifetime (MTBF = 250,000 hrs = 28 years :running 24/7, and 500+k hours is more typical today). The units for MTBF are not hours but device-hours, i.e., the product of the number of hours and the number of devices being observed, and that rating applies only during the device's rated service life, which is an entirely separate parameter. MTBF of 250,000 is almost totally unrelated to the expected service life. It is quite possible to have a device with its MTBF 250,000 and a rated service life of 1 hour. It just means that if you ran 250,000 of those devices for one hour you should expect 1 failure. Once a device passes its rated service life, the MTBF rating no longer applies. Think: a battery used to provide power to a missle's guidance system -- built to be highly reliable for the short time it's needed, and pretty much assured to go dead not long after that. High MTBF, short service life. Looking at the power-on hours and corresponding normalized SMART value on a few fairly recent drives, it appears that the SMART warning due to power-on hours would come at about 10 years of power on. That is total BS. MTBF is per device. Read, for example, MIL-HDBK-217. -- Cheers, Bob |
#13
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Unusual drive failure - 12v line short
In article , Clint Sharp
writes More likely to be a transorb but most likely to be the motor driver IC. They usually burn up when they fail, and this one looked fine. Took out the shorted diode and the drive span up ok. Not yet tried it. -- (\__/) (='.'=) Bunny says Windows 7 is Vi$ta reloaded. (")_(") http://imgs.xkcd.com/comics/windows_7.png |
#14
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Unusual drive failure - 12v line short
In article , 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 |
#15
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Unusual drive failure - 12v line short
In article ,
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" |
#16
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Unusual drive failure - 12v line short
In comp.sys.ibm.pc.hardware.storage Robert Nichols wrote:
In article , 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 |
#17
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Unusual drive failure - 12v line short
"Mike Tomlinson" wrote in message ...
In article , 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. |
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