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ground wire question

Discussion in 'Electrical Engineering' started by DJ, Jun 5, 2004.

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  1. Guest

    He said flickering. Whether you wish to quibble on flickering vs dimming,
    he's got a symptom that could be a disaster in the making, and is a probable
    cause of his PC problem. It is the first thing to address.
    Again, a non-specific reference to leakage voltages. Specify the leakage:
    where is it and what causes it? For example, lets say you have 60+ volts
    on the PC chassis with respect to ground, due to a leaky capacitor.
    The correct fix is to replace the capacitor. You need to specify what you
    are thinking of when you talk about "60 Hz leakage voltage"
    You may have seen it, but you have not identified the source of
    the leakage, nor stated where the voltage existed. Where did
    you connect your meter leads? How did you determine it
    was "leakage" voltage and what do you mean by "leakage"?
    How did you determine it was 60 Hz?

    If some component is leaking such that it creates a condition
    where 60+ volts (with respect to some point you have not yet
    identified) exists where it shouldn't, then isn't replacing the defective
    component the correct fix? (I mention 60+ volts, as that is the figure
    you used in a previous post. ) If the chassis of a PC is at 60+
    volts (or some other objectionable voltage) with respect to ground
    due to a leaking capacitor, and that is causing the PC to drop power,
    installing an equipment grounding conductor very well might make
    the PC stop dropping power. You haven't resolved the problem,
    you've only hidden it. The correct thing to do is determine the
    source of the problem and fix whatever is causing it.

    Because you are unable/unwilling to specify what you are talking about,
    you deremine that someone else is not a digital logic designer (or a piano
    tuner or a farmer or whatever)??? That makes no sense.
    The answer is NO, with no equivocation. You need some condition
    other than a missing equipment grounding conductor, to cause a PC to
    drop power when it should not. The NEC prohibits using the egc as
    a current carrying conductor. Perhaps you don't understand the
    distinction, since it is NEC terminology. It means that manufacturer
    and designers cannot intentionally design or build a PC that requires
    the egc to carry current under normal conditions. It is for safety only.

    Look, this should be simple. You claim that some PC's need the
    egc to avoid the symptom that the OP asked about - dropping
    power. You say designers use the egc to prevent that. What are
    the specifics you have in mind? How do the designers use the egc
    to accomplish this? What is the circuit?

    <snip>
     
  2. w_tom

    w_tom Guest

    If safety ground is only to short out fault currents, then
    why were HP LaserJet II printers damaged - hardware damaged on
    input (centronix) port - due to a problem created by the
    missing safety (third prong) ground? Read what Hobdbcgv has
    posted rather than snipping what you don't understand. A
    missing safety ground can cause a computer to not perform
    properly. And again, that problem would be unique to that
    computer's design.

    In the meantime ... DJ. You have been asked many
    questions. You have been provided with some experiments that
    you should have performed. Time to read back those posts and
    answer the questions. Currently you have not replied with the
    answers to questions necessary to solve you original problem.
    As a result, this thread is breaking down as others are now
    throwing hand grenades into the discussion. By now you should
    have been answering some of those questions and reporting
    back. Please hurry before this whole thread turns into
    volcanic lava.
     
  3. --

    -- Guest

    What TH does that mean? The statement makes no sense at all - it's like
    saying "it's not a ground, it's a green wire connected between the neutral
    bus and an earthing rod".

    A bond is a wire is a lead - all ground paths.

    (Particularly in printers with the charge buildup from moving paper and
    moving rubber, when the anti-static brushes are undersized and the ground
    path is inadequate, and the charge naturally seeks another path.)
     
  4. w_tom

    w_tom Guest

    An old issue of Datamation Magazine told a classic story.
    New mainframe was installed but kept failing. At night, the
    tech would run diagnostics and suffer no failures. But
    everytime the tech left for coffee, then computer would
    crash. It got so bad that the tech would loudly announce he
    was leaving for coffee, stomp out the door, then sneak back to
    peek in and watch the computer. Still that computer was so
    smart that it would not crash, until tech actually left for
    coffee.

    Turns out the computer was grounded (bonded) to a same point
    as the elevator. Only when the tech actually left on the
    elevator, would the computer crash. Again, if and how a
    computer is bonded (grounded) can affect reliability.
    Computers are not haunted. They fail only for good, technical
    reasons. Some are designed assuming the safety ground exists.

    We are probably talking about different printers. Centronix
    cables were limited to about 15 feet. Printer had to be
    adjacent to computer. Centronix interfaces to HP LaserJet II
    printers were damaged by missing safety ground. IOW computer
    and printer were therefore not bonded to a common point which
    is what a missing safety ground created. Normally printer did
    not have a bonding wire to computer because manufacture
    *assumed* the safety ground would be provided. Again
    demonstrates how a missing safety ground can cause unusual
    failures. (Coffee had nothing to do with that solution
    either.)
     
  5. Louis Bybee

    Louis Bybee Guest

    I have resolved multiple instances where data equipment failure, and data
    throughput issues were a result of devices with differing ground or chassis
    potential in relation to earth ground. In most cases they were separated far
    enough to be served by different branch circuits. In these cases significant
    current would flow on the data reference ground where each chassis was at a
    different potential in relation to each other (often just momentarily). In
    almost every case there were cheap shunt mode surge suppressors involved
    that were polluting the grounding conductor on one end of the interconnected
    devices.

    I have observed instances where the integrity of data equipment had suffered
    due to the lack of, or a poor quality grounding conductor. As related above
    having a quality grounding path present at a piece of data equipment isn't a
    guarantee of trouble free operation.

    Louis
     
  6. Louis Bybee

    Louis Bybee Guest

    I have resolved multiple instances where data equipment failure, and data
    throughput issues were a result of devices with differing ground or chassis
    potential in relation to earth ground. In most cases they were separated far
    enough to be served by different branch circuits. In these cases significant
    current would flow on the data reference ground where each chassis was at a
    different potential in relation to each other (often just momentarily). In
    almost every case there were cheap shunt mode surge suppressors involved
    that were polluting the grounding conductor on one end of the interconnected
    devices.

    I have observed instances where the integrity of data equipment had suffered
    due to the lack of, or a poor quality grounding conductor. As related above
    having a quality grounding path present at a piece of data equipment isn't a
    guarantee of trouble free operation.

    Louis
     
  7. w_tom

    w_tom Guest

    50' was not supported. But I used twisted cable techniques
    and shielding to make it work. Then I discovered the
    handshaking was not controlled by DOS. Some programs would
    work. Others would not. Eventually had to go with a printer
    network. Don't something outside of specs does not mean it
    will fail every time. Just may fail sometime.

    Any rate, that printer on 50 foot cable using power and
    safety ground from a different receptacle could cause ground
    problems that resulted in garbled data or hardware failure.
    Failure that could be made more likely by a missing safety
    ground when power plug has three prongs - assumes safety
    ground will be provided.
     
  8. DJ

    DJ Guest

    "w_tom"
    Hi, sorry I haven't written back to the group sooner. I was trying to see
    if I could figure out what was running at the time of the shutdowns. No
    matter what I have tried the PC has not shut down again. I even left it on
    for 48 hours with no problems. Strange.
    I appreciate all the information from you and all that replied. I didn't
    mean to cause any conflicts over all of this. If I have anymore problems, I
    will let you all know.
    Thanks again,
    Donna J.
     
  9. w_tom

    w_tom Guest

    Did you review the event logs provided by your operating
    system as noted in a 6 Jun post? History that the system
    stores on all detected failures. Did you put a large load (ie
    electric heater) on that circuit while an incandescent bulb
    was on? Did the bulb dim and the previously noted 3.5 digit
    meter show a major voltage drop - as posted 7 Jun? Is it
    dimming or flickering as was asked on 6 Jun?

    These are not just to fix your computer. Do you intend to
    be alive next year? Intermittent computer failure may have
    only been a 'canary in the coalmine'. Important experiments
    that you were expected to perform because experiments were
    about something more than just a crashing computer.
    Experiments also eliminated human threats as a reason for
    computer crash.

    Your failures are not strange to an engineering mentality
    that constantly deals with realities. Many failures start this
    way before things like, worst case, explosions happen. Those
    intermittent crashes are consistent even for problems,
    potentially dangerous, and existing elsewhere. Noted was that
    you problem could be the precursor to something resulting,
    worst case, in a building fire. Provided were simple
    experiments to isolate the problem, at minimum, to something
    insignificant.

    In the meantime as asked in your original post, yes, missing
    safety ground can cause strange events, including crashes, on
    some properly built machines and not on others.

    Please go back, read those posts, and report back. Do not
    selectively perform only what is convenient. Those simple
    experiments were dependent on each other to isolate your
    problems. Three things posted above should be performed
    immediately regardless of whether crashes today or not.
    Currently, we don't even know if you have only dimming or have
    flickering.
     
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