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Capacitor failure

  1. Jul 18, 2011 #1
    For those EE that have heard of, but not seen, here is a photo of capacitor failure on a motherboard.

    I have labelled the relevant material.
     

    Attached Files:

  2. jcsd
  3. Jul 18, 2011 #2

    berkeman

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    Staff: Mentor

    Were you fixing it at the time? :biggrin: (see your footer)


    Did the supply overvoltage to cause that?
     
  4. Jul 18, 2011 #3
    Rumbled!

    :rofl:

    No, this mobo (probably) died of heatstroke.
     
  5. Jul 19, 2011 #4
    I've got one too. Maybe I'll post a pic of that later today.
     
  6. Jul 19, 2011 #5
    One aspect of capacitors I never see described is current capacity. They only have a voltage rating. Could it be that for a given capacitance, voltage, and frequency, they can always handle the current that would be involved continuously? Or is there really a limit?

    If these capacitors overheat, isn't that more directly an issue of current flow? If the metal inside is too thin for the specified usage, they would get too hot, right? Then there should be either an ambient temperature limit, or a heat rise rating. But that can also depend on air flow, etc. I so often seen gangs of little capacitors all tucked together. That doesn't let the heat early and we end up with the magic smoke being let out later.
     
  7. Jul 19, 2011 #6
    Not in this case.
    T'was a seriously abused pc, running 24/7 and the environment inside the case just too hot for too long.
     
  8. Jul 19, 2011 #7

    berkeman

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    Look for the "ripple current" specification in the datasheets...
     
  9. Jul 19, 2011 #8

    dlgoff

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    I was wondering about Power Factor compensation capacitors for inductive loads and what causes their failure and came across this about "Harmonic Overloading of Capacitors". It's from the Galco Industrial Electronics, Inc. site.
    http://www.galco.com/circuit/PFCC_har.htm" [Broken]
     
    Last edited by a moderator: May 5, 2017
  10. Jul 19, 2011 #9
    Not relevant but:



    I get chills every time i watch this.
     
    Last edited by a moderator: Sep 25, 2014
  11. Jul 19, 2011 #10
  12. Jul 19, 2011 #11

    Averagesupernova

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    It's been a while since I've seen that one. A bit scary. I don't recall where and there may be plenty others linked on youtube but there are alot of other vids on the net that show similar things. My favorite was a transformer that went up in what appears to be someone back yard.
     
    Last edited by a moderator: Sep 25, 2014
  13. Jul 19, 2011 #12

    MATLABdude

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    A lot of really cheap capacitors came on the market supposedly after a little industrial espionage wherein a disgruntled scientist at one of the Japanese components firms stole the formula for electrolyte and sold it to manufacturers in Taiwan and China:
    http://spectrum.ieee.org/computing/hardware/leaking-capacitors-muck-up-motherboards

    Since it wasn't the complete / correct formula, this led to a lot of faulty motherboards, from both low and high-end manufacturers (the capacitor plague):
    http://en.wikipedia.org/wiki/Capacitor_plague

    I thought it was basically a late 90s, early 2000s sort of problem, but I had to replace cheap bulged caps in the power supply board of an LCD (Samsung 205BW) from 2007 with high-temperature, low ESR, and high lifetime ones (Nichion).

    4grywg.jpg

    I generally like Samsung products, but I hear this is quite an endemic problem with them.

    For those of you in a similar predicament, this site was quite helpful:
    http://www.badcaps.net/forum/showthread.php?t=11439
     
  14. Jul 19, 2011 #13
    A capacitor made for pulsed service often has a maximum dV/dt rating. This can be related to a maximum pulsed current through the capacitance.

    Ripple specs are important for internal heating of the cap. The dV/dt spec is a matter of instantaneous peak internal current above which you damage the electrodes.
     
  15. Jul 20, 2011 #14
    Last edited: Jul 20, 2011
  16. Jul 24, 2011 #15
    hey what about the condition of that 1st one from left in the first pic?
     
    Last edited by a moderator: Jul 25, 2011
  17. Jul 24, 2011 #16

    MATLABdude

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    Same thing as in the others: exuded electrolyte (or a really dirty camera lens)
     
    Last edited by a moderator: Jul 25, 2011
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