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Did low voltage cause the pc to fail?

Discussion in 'Electronic Basics' started by Greg, Aug 19, 2004.

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  1. Greg

    Greg Guest

    G'day from a long way away....

    I am struggling with an argument about a couple of damaged home
    computers and I was wondering if anyone can help????

    The switchboard for a suburban house was replaced in November 2003.
    Since February 03 various appliances in the house have failed,
    including three pcs. The owners believe that lower than stat limits
    voltage into the residence caused the failure. Since the switchboard
    was replaced the problems have stopped.

    Their electrician said that the switchboard was a 30 year old
    porcelain-fused model and was burning out on the busbar and the
    circuits on the board were overloaded with too many appliances.

    My question to you, if you would be so kind...."What chance is there
    that the slightly under supply of grid voltage would severely damage
    pcs, or, is the pc damage more likely to be as a result of the arcing
    at the switchboard?"

    Brisbane, Queensland, Australia
  2. We would need to know the nature of the PC failure. The only component of
    the PC that could possibly fail due to a mains power problem is the power
    supply, because its output is regulated -- it either outputs the right
    voltages at full current, or shuts itself off completely.

    It might over-exert itself stepping up a lower-than-normal input voltage...

    Also, power cutting on and off repeatedly (a lot of "flickering") might
    damage the power supply or even, I suppose, a disk drive or something. Did
    that happen?
  3. James Sweet

    James Sweet Guest

    Either undervoltage or arcing can damage equipment.
  4. w_tom

    w_tom Guest

    Unervoltage - also known as a brownout - does not damage electronics.
    Unfortunately too many take what they learned about motors and
    expolate that to knowledge about electronics. One must first learn
    basic concept before making assumptions such as low voltage will
    damage a computer.

    The Intel specs are quite bluntly clear about this. AC mains
    voltage can drop so low that incandescent bulbs are at less than 40%
    intensity. Even at that low voltage, a computer with a full load of
    peripherals must power up and run normally. Where is the damage? It
    only exists in a world where people don't learn simple technologies
    nor read manufacturer numerical specs.

    What is a shutdown? Power is removed. Electrolytic capacitors
    slowly discharge. The computer suffers a brownout - diminished
    voltage. So the computer is damaged? Of course not. Computer must
    work just fine until voltage becomes too low - and then it must switch
    to a no more output mode. IOW a shutdown is a brownout that
    eventually becomes a blackout. But if brownouts - low voltage - cause
    hardware damage, then a shutdown will also damage hardware.

    Can computers be damaged by a brownout? Well if it is, then the
    computer fails to mean numerous industry standards and defacto
    standards that have exists longer than most every reader here. The
    answer to the OPs question is found in those specs. If undervoltage
    damages the electronics, then the human knows exactly what the reason
    for failure was - the human.
  5. Intel doesn't make PC power supplies. Sometimes we don't know *who* makes
    them. I wouldn't put it past them to have something that would fail (or at
    least blow a fuse) when subjected to undervoltage.

    After all, undervoltage requires the switching power supply to draw *more*
    current (as it gets less voltage).
  6. In an ideal world this would be so.

    In the real World, it's quite possible that brownouts can cause
    switchmode power supplies to fail.

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  7. w_tom

    w_tom Guest

    In the real world, only those with a bean counter mentality
    have power supplies damaged by brownouts. When a power supply
    is damaged by a brownout, then the reason for failure is
    directly traceable to a human who failed to learn basic

    Again - what is a power down or shutdown? A brownout that
    eventually becomes a blackout. If brownouts damage
    electronics, then so does turning the power off. This alone
    is a damning fact. Brownouts do not damage properly
    constructed electronics. Shutdown also does not damage those

    Even in those cited links, I find no reference to brownouts
    causing electronics damage. The CBEMA specifically states
    that all equipment must not be damaged by low volts. They and
    other industry standards - including the computer industry
    standard originally created by Intel - are quite blunt about
    this. Brownouts don't cause electronics damage. Stated
    bluntly even in specs.

    Intel defines how computer power supplies must operate.
    IBM, Dell, AMD, and a long list of other responsible
    manufacturers also demand same standards be met. But this is
    old technology - older than most lurkers have even existed.
    However many bean counters buy 'dumped into North America'
    power supplies to cut costs. Power supplies that violate
    basic Intel requirements. Then those silly bean counter
    mentalities try to blame others; then claim brownouts damage
    electronics. Where is the logic in that? Its called

    Numerous industry standards for ATX power supplies were the
    same defacto standards of 30+ years ago. Such defective
    supplies are not found in brand name computers. Dumping only
    works at great profit to the Asian manufacturer when a
    computer assembler does not even have basic electrical
    knowledge - buys power supplies on price rather than upon
    technical specifications.

    If anyone says that a brownout can damage properly designed
    electronics, then we have a benchmark for a bean counter
    mentality masking as technically knowledgeable.

    Those who think otherwise are then invited to explain how
    the individual components inside the power supply fail due to
    brownout. That's right. I design at the component level -
    not just rack and stack black boxes like a computer assembler
    who need not have any electrical knowledge. Please feel free
    to describe how that electrolytic capacitor or power
    transistor is damaged by a brownout. One must be that
    knowledgeable to foolishly claim brownouts damage electronics.
  8. w_tom

    w_tom Guest

    That's all good and nice reasoning which the designer
    already considered when he designed a power supply that is not
    damaged by brownouts. There is even a circuit inside the
    supply that cuts off power IF the supply cannot maintain
    required output voltages. Same circuit also sends a signal to
    motherboard. Again, no damage to hardware.

    Intel does not make power supplies? Underwriters Laboratory
    - UL - does not make anything. Therefore UL standards don't
    exist either?

    If a computer power supply is damaged by the brownout, then
    the brownout is not a reason for failure. That failure is
    directly traceable to the human who typically buys on price
    rather than first learn basic electricity concepts.

    If the power supply does not come with written specs -
    things they actually claim to do - then one should assume the
    worst. These same 'discount' power supplies are sold to
    computer assemblers who would blame the brownout rather than
    blame themselves. Brownouts do not damage properly
    constructed power supplies. Unfortunately those supplies cost
    more money. Bean counter mentalities fear spending money.

    I bought my power supply from some guy wearing a black
    trench coat and it failed? That proves brownouts cause
    computer damage? Unfortunately too many computer assemblers
    who don't even have basic electrical knowledge use that
    reasoning. A power supplies damaged by a brownout was
    defective the minute it was purchased.
  9. Bob Myers

    Bob Myers Guest

    And, of course, every PC ever produced anywhere in the world
    IS by definition completely, utterly, and totally compliant with
    Intel's specs, right? :) :) :)

    Ah, to live in such a world....

    Bob M.
  10. Bob Myers

    Bob Myers Guest

    Or so you hope.

    One of the things I used to do (in a past life, but for my
    current employer) was to supervise the environmental, etc.
    qualification testing of new products. Do you think we
    never EVER found problems with power supply design
    that showed up in the AC line compatibility testing?

    It would be a truly wonderful world in which everything
    was designed as it should be, in which everything was
    actually BUILT per those designs, and in which the
    components that went into that construction never ever
    had any sort of problem of their own. Just as soon as
    you find that world, you let us know.
    Both Intel-generated specifications exist, and UL standards
    exist. And so, according to you, everything ever
    designed and built automatically complies with those
    standards? Hallelujah! I can call down to the test lab
    right now, and tell those guys to take it easy! There's
    nothing more for them to do!!!!
    First, it's hardly reasonable to expect anyone who buys
    a power supply to be sufficiently educated in power
    supply design so as to recognize a good design or a bad
    one at first glance. (Hey, if they're THAT good, they should
    be designing and building their OWN, and then I know several
    places that will likely want to hire them!) Second - you again
    show an awful lot of faith in the mere presence of "written
    specs." Many aren't worth the paper they're printed on. long as they were properly designed AND
    constructed, built from perfect components, and have
    suffered absolutely no ill effects due to age, electrical
    or mechanical stress, etc., since being built. By this same
    sort of reasoning, I should be able to claim that NOTHING
    which is "properly designed and built" should ever fail. Once
    again, the reliability guys will be SO glad to hear that...

    Bob M.
  11. Bob Myers

    Bob Myers Guest

    May I ask just how many years experience YOU have in
    power supply, design, and construction in the commercial
    world (i.e., actually shipping this sort of product in volume)?

    Bob M.
  12. Ban

    Ban Guest

    Your ignorance is really showing up. If the specs are not met, that supply
    goes back on guarantee and it eventually will drive this supplyer out of
    business. In Europe we have now a 2years guarantee by law and believe it or
    not, when a part fails because of undervoltage the seller has to take it
    back and repair/replace it.
    It is a criminal offense if UL-specs are not met, and if any personal injury
    happens you will pay big bucks. There is a responsability involved and if
    you fake the CE or UL or whatever rules apply in your country, you will be

    Mr Meyer, you must be one of those bean counters. What a stupid and arrogant
    commentary. The consumer has a lot of laws on his side and especially in the
    US you better not deliver any sub-spec mercendise declared as being ok. If
    you buy at the surplus store or Ebay, you might end up with what you are
    descibing, but this stuff is not guaranteed meeting the specs.
  13. Here in the US we have 240/120 supplied to homes. If the grounded conductor
    fails, the voltage can divide up as 100 and 140 or as 80 and 160 and so on
    depending on the loads at the time. Maybe that's what happened and it was
    overvoltage that fried the computers.
  14. Bob Myers

    Bob Myers Guest

    So if it fails within that 2 year period, great; do you believe
    that all suplies which fail due to an undervolt condition are
    within their warranty period? Or that simply because a
    failure DOES occur within the warranty period, that this
    MUST be indicative of a sufficiently widespread problem such
    that the supplier WILL be "driven out of business?"

    Again, if your model is correct, power supplies that don't meet
    spec should never be found in the real world. I claim that
    such things do, in fact, exist. Care to bet which of us can
    support their position through evidence?

    As to "my ignorance really showing" up, you're right - after
    25+ years as an engineer working for one of the major
    computer companies, I clearly don't know squat about the
    realities of the electronics manufacturing business.
    Actually, it isn't, although that is a widespread misconception.
    The UL standards do not carry the force of law, nor is there
    any law making it a criminal offense to sell a product which is
    not UL certified or registered. UL compliance can and will
    enter into liability awards resulting from failed products, but
    that is a civil issue, not a criminal one. Further, simply obtaining
    UL certification basically just says that, IF built as designed
    from the specified components, the product can reasonably be
    expected to meet the specification in question. The nature
    of testing and statistics being what it is, this can never be a
    perfect assurance of 100% compliance, unless the product in
    question is subjected to extensive finished-product testing
    in 100% of the units shipped. Especially for consumer goods,
    this is basically never the case, with the exception of a few
    key specifications. And no testing can ever be a 100%
    guarantee of continued compliance for all time, for the reasons
    mentioned earlier having to do with aging, electrical and
    mechanical stress, and so forth.
    Yes, but that's not what's being discussed here. Forging
    a UL mark is irrelevant to the topic under consideration, which
    is the reliability and failure modes of power supplies.

    Nope; I am not now, nor have I ever been, a "bean counter."
    It is simply a fact of life that NOT all products shipped will
    meet their published specifications 100%, and those which do
    will not continue to do so forever. Again, if you feel otherwise,
    please call up the head of our service and support organization, and
    inform them that everyone can go home now.

    What published specifications really mean, from a legitimate supplier,
    is that IF the product delivered does not meet the specifications
    (which generally can be considered as being a part of the purchase
    agreement - i.e., you did not agree to buy THIS product, but instead
    you actually agreed to buy a product which met these specifications),
    then you have the right to return it and expect a replacement. But
    simply publishing the specifications by no means is perfect assurance
    that every product shipped/received WILL actually meet its specs
    when it reaches the customer. SOMETIMES, this is due to shoddy
    design and/or manufacturing - but even the best manufacturer in the
    world for whatever product you're considering still has the occasional
    failure-upon-delivery. Welcome to the real world.

    Bob M.
  15. dude

    dude Guest

    Isn't the question whether the PC failed or not?

    I wouldn't consider the power supply the PC itself. I guess you could argue
    that point but the power supply is a part that is made to fail, if
    necessary, to prevent further internal damage to the PC. I've replaced many
    power supplies on PCs that were struck by lightning (not directly, I'm
    sure), the power supply was fried but the PC itself was fine after a new
    supply was installed.
  16. Jim Phelps

    Jim Phelps Guest

    Hi Greg, I'm not going to take the time to read all of the answers you
    have gotten. Remember what Abe Lincoln said, Beleive only half of what
    you see and nothing of what you hear. My two cents is this: MOST
    switching power supplies and probably all used in computers are rated
    from 90 to 150 volts set to 120v and double that when set to 240. Our
    engineers, way back in about 1985 built one that was to tolerate 90 to
    300 without a switch to set the input voltage. It didn't make it, but
    was great when the switch was added. Luck, Jim
  17. ~Dude17~

    ~Dude17~ Guest

    X-No-Archive: Yes

    Do you have the detailed description of failure? Poor quality power
    supplies have a disgustingly low hold up time and even the best power
    have a limited hold up time.

    Hold up time is the amount of time the power supply can sustain proper
    outputs when input power is lost. Usually, when power goes out or
    browns out severely briefly but longer than the hold up time, the
    computer will reboot suddenly. If it happens at just the right time,
    it can corrupt the HDD. I've heard of power supplies that's so crappy
    that computer reboots when UPS tranfers to battery, because it it
    couldn't hold up during a ~5mS transfer time.
  18. James Sweet

    James Sweet Guest

    Undervoltage most certainly *can* damage electronics, some poorly designed
    SMPS's will attempt to compensate for the low line voltage and blow
    themselves up. Properly designed equipment won't do this, but there's a
    great deal of poorly designed junk on the market these days.
  19. James Sweet

    James Sweet Guest

    I think anyone who actually works on real world products will quickly come
    to this same conclusion. Like it or not, there's a lot of pure garbage that
    ends up on store shelves. For every well designed piece of equipment I work
    on, I come across at least half a dozen things that make me want to find the
    engineer who designed it and smack them over the head with the thing.
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