Holy Moly -- Residual Electricity????

Discussion in 'Dell' started by Prisoner at War, Nov 5, 2007.

  1. Prisoner at War

    M.I.5¾ Guest

    Regardless of all the theories involving capacitors storing charge, the
    power supply is shot (and it is most likely a faulty capacitor that is
    responsible - that is one that is failing to store charge until it cools off
    a bit).
     
    M.I.5¾, Nov 13, 2007
    #61
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  2. Prisoner at War

    Androcles Guest

    :
    : : >
    : > Is there some such concept as "residual electricity"???
    : >
    : > There was a problem with a computer at work...it's a new Dell running
    : > WinXP Pro...everything's fine, I go to lunch and come back to a blank
    : > screen that won't wake up from power-save/sleep mode!! I do the
    : > obvious and check connections, making sure they're secure and
    : > whatnot. I turn off the computer and turn it back on a few times, to
    : > no effect!
    : >
    : > Tech Support suspects some kind of a "power management" issue --
    : > whatever that is -- and suggests that I leave the system off for a few
    : > minutes, literally, to let things "clear"...whatever that means. Sure
    : > enough, however: it works!
    : >
    : > So now I'm here asking, because Tech hasn't the time to puzzle over it
    : > with me, WHAT HAPPENED??? And how come shutting off power for a few
    : > seconds isn't comparable to leaving power off for a few
    : > minutes????????????
    :
    : Regardless of all the theories involving capacitors storing charge, the
    : power supply is shot (and it is most likely a faulty capacitor that is
    : responsible - that is one that is failing to store charge until it cools
    off
    : a bit).

    Then when you swap out the PSU it turns out to be a problem
    on the motherboard - Saudde's law.
    Unless you changed out the motherboard first, in which case it was
    the PSU - Murphy's law. And really, Tech doesn't have the time
    to analyse it poking around with a voltmeter and staring at the
    schematic when it only cost a few bucks to replace the module.
    Gone are the days when you replaced a burnt out resistor
    or an exploded capacitor in a TV, it's cheaper to buy a new TV
    now.
    As for computers, I've got three spare ... nothing wrong with them,
    they are just too slow to bother with and who needs a 1 Gig
    hard drive when you can get 320 Gig or whatever?
     
    Androcles, Nov 13, 2007
    #62
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  3. Prisoner at War

    Unknown Guest

    What type of capacitor has to cool off before it accepts a charge?
     
    Unknown, Nov 13, 2007
    #63
  4. Prisoner at War

    M.I.5¾ Guest

    A: A faulty one.

    It is well a known problem particularly among certain types of electrolytic
    capacitors. The usual problem is that the EPR (Effective parallel
    resistance) of the capacitor falls alarmingly as it warms up rendering it
    ineffective as a capacitor.
     
    M.I.5¾, Nov 14, 2007
    #64
  5. Prisoner at War

    Unknown Guest

    How do you dream up all these ridiculous things?
     
    Unknown, Nov 14, 2007
    #65
  6. Prisoner at War

    Androcles Guest

    Sounds like a short circuit to me. Perhaps he's connecting
    them with the wrong polarity of the "certain type".

    : How do you dream up all these ridiculous things?
    : : >
    : > : >> What type of capacitor has to cool off before it accepts a charge?
    : >
    : > A: A faulty one.
    : >
    : > It is well a known problem particularly among certain types of
    : > electrolytic capacitors. The usual problem is that the EPR (Effective
    : > parallel resistance) of the capacitor falls alarmingly as it warms up
    : > rendering it ineffective as a capacitor.
    : >
    : >
    : >
    :
    :
     
    Androcles, Nov 14, 2007
    #66
  7. Prisoner at War

    Randy Poe Guest

    Randy Poe, Nov 14, 2007
    #67
  8. Prisoner at War

    Unknown Guest

    What caused the high temperature?
    Two charts of electrolytic capacitor failure modes. Check out
    Table 2 here:
    http://industrial.panasonic.com/www-data/pdf/ABA0000/ABA0000TE4.pdf

    Operating at high temperature is shown to cause failure
    by increase in leakage current.

    or Figure 2.10 here:
    http://etd.gatech.edu/theses/available/etd-04082007-083102/unrestricted/imam_afroz_m_200705_phd.pdf

    Operating at high temperature is shown to cause failure
    by loss of effective resistance (i.e. increased leakage).

    - Randy
     
    Unknown, Nov 14, 2007
    #68
  9. Prisoner at War

    Randy Poe Guest

    Being in a hot place.

    - Randy
     
    Randy Poe, Nov 14, 2007
    #69
  10. Prisoner at War

    Unknown Guest

    Then the failure occurred BEFORE the capacitor went bad.
     
    Unknown, Nov 14, 2007
    #70
  11. Prisoner at War

    Randy Poe Guest

    Um, what? You mean just the fact that I *try* to
    operate a capacitor in a poorly air-conditioned room
    implies it has failed?

    Or do you mean that just the fact that the temperature
    around my circuit board is above room temperature
    implies that something has failed?

    Or what?

    - Randy
     
    Randy Poe, Nov 14, 2007
    #71
  12. Prisoner at War

    RnR Guest


    It would have to be pretty hot of at least above 120F tho I've seen
    some hardware listed in the 140's F as maximum. My guess is the 2nd
    applies here. Now the problem is what causes the high temperature to
    begin with?? I have doubts about a bad fan but perhaps or maybe a
    short circuit????
     
    RnR, Nov 14, 2007
    #72
  13. Prisoner at War

    Randy Poe Guest

    This all seems incidental to the discussion. There was
    doubt raised on the point that high temperatures could
    cause failure of electrolytic capacitors. Let's say that
    the high temperature is out of spec for the board. Let's
    say that something else HAS failed. How does that
    bear on the discussion of this failure mode for capacitors
    exposed to high temperatures and whether or not it's
    a "ridiculous thing" to say that high temperatures will cause
    this effect on electrolytic capacitors?

    - Randy
     
    Randy Poe, Nov 14, 2007
    #73
  14. Prisoner at War

    Bruce Guest

    All fluid filled electrolytic capacitors will eventually fail.
    The important point is that the expected lifetime shortens dramatically
    as the temperature rises.
     
    Bruce, Nov 14, 2007
    #74
  15. Prisoner at War

    Androcles Guest

    : > : >
    : > >> What caused the high temperature?
    : >
    : > > Being in a hot place.
    : >
    : > Then the failure occurred BEFORE the capacitor went bad.
    : >
    :
    : Um, what? You mean just the fact that I *try* to
    : operate a capacitor in a poorly air-conditioned room
    : implies it has failed?

    It is your claim that the failure has an environmental cause.
    Do not operate capacitors in a poorly air-conditioned room,
    they will fail (according to Poe). Um, yes.
     
    Androcles, Nov 15, 2007
    #75
  16. Prisoner at War

    Androcles Guest

    : > On Wed, 14 Nov 2007 10:07:49 -0800, Randy Poe <>
    : > wrote:
    : >
    : > >> What caused the high temperature?
    : >
    : > >Being in a hot place.
    : >
    : > > - Randy
    : >
    : > It would have to be pretty hot of at least above 120F tho I've seen
    : > some hardware listed in the 140's F as maximum. My guess is the 2nd
    : > applies here. Now the problem is what causes the high temperature to
    : > begin with?? I have doubts about a bad fan but perhaps or maybe a
    : > short circuit????
    :
    : This all seems incidental to the discussion.

    Bullshit, it is your claim that capacitor failure has an environmental
    cause, that is most pertinent to the discussion you contributed to.
     
    Androcles, Nov 15, 2007
    #76
  17. Prisoner at War

    w_tom Guest

    Temperature has what relevance to the problem? Unfortunately, many
    want to blame temperature when other functions are not understood.

    Computers must work just fine even when room temperature is above
    100 degree F. In fact, testing a computer in a 100 degree room is one
    way to find defects because the defect results in failure.

    Electrolytic capacitors inside power supplies are typically rated
    for higher temperatures. One failure mode is Effective Series
    Resistance or ESR (not Parallel Resistance). If chemistry inside the
    electrolytic is failing, then series resistance increases. Higher
    resistance means capacitor gets hotter - a feedback cycle that
    eventually causes capacitor failure.

    But this is not relevant to a power supply operating on 240 volts AC
    when the power supply is rated for 240 volts.

    Electrolytic failure is most often a manufacturing defect inside the
    capacitor or excessive voltage applied to that capacitor. Capacitors
    are routinely selected to withstand temperatures well above standard
    room temperature. Its temperature rating is usually printed on that
    electrolytic. Long before accepting what was posted, view those
    numbers yourself.
     
    w_tom, Nov 15, 2007
    #77
  18. Prisoner at War

    M.I.5¾ Guest

    It's not a short circuit as such, just a lower resistance in parallel with
    the capacitor. It's enough to prevent the switching circuit from switching.
     
    M.I.5¾, Nov 15, 2007
    #78
  19. Prisoner at War

    M.I.5¾ Guest

    Two charts of electrolytic capacitor failure modes. Check out
    Table 2 here:
    http://industrial.panasonic.com/www-data/pdf/ABA0000/ABA0000TE4.pdf

    Operating at high temperature is shown to cause failure
    by increase in leakage current.

    or Figure 2.10 here:
    http://etd.gatech.edu/theses/available/etd-04082007-083102/unrestricted/imam_afroz_m_200705_phd.pdf

    Operating at high temperature is shown to cause failure
    by loss of effective resistance (i.e. increased leakage).

    -----------

    Indeed. In general electrolytic capacitors are rated at either 85°C or
    105°C. The former is obviously cheaper than the latter and that's often
    what gets used as such supplies don't run that warm. However, even if
    operated below 85°C, the former type are considerably more unreliable than
    the latter.
     
    M.I.5¾, Nov 15, 2007
    #79
  20. Prisoner at War

    M.I.5¾ Guest

    Apparently well to known to nearly everyone - but not you.
     
    M.I.5¾, Nov 15, 2007
    #80
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