Can a bulging electrolytic capacitor still be good?

Discussion in 'Shock Brother's DIY Amps' started by brokenbones, Apr 18, 2019.

  1. brokenbones

    brokenbones Tele-Meister

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    I was doing some prep work for a recap and decided to test a bulging capacitor still in circuit. One of the ESR meters I use has that capability. Anyways, the capacitor tested good, great actually. I'll probably pull it to double check with a different meter. Is this possible?

    If it tests good out of circuit would it be okay to leave it in? The reason I ask is that I intended to replace it, because of the bulge, but the replacement I bought is too tall. It's a $5+ cap from mouser and even more expensive locally. Could this be a false reading?
     
  2. Dacious

    Dacious Poster Extraordinaire

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    If it's oozing stuff it's likely to pop. I'd change it.

    When they let go, the electrolyte is like acidic Araldite.
     
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  3. boredguy6060

    boredguy6060 Friend of Leo's

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    It’s good right up until it isn’t, then it causes serious damage and inconvenience.
    Change it, it’s not worth the risk.
     
  4. telemnemonics

    telemnemonics Doctor of Teleocity

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    I can play in tune on strings so worn out the windings are coming off at the frets where they were worn through.
    So measurements aren't always a good measure!
     
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  5. RLee77

    RLee77 Friend of Leo's

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    That’s kind of like asking if it’s ok to eat meat that smells off.
    You might get away with it, but is it really worth the risk?
     
  6. stratclub

    stratclub Tele-Meister

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    Or continuing to drive on a tire with a tread separation developing. It holds 32 PSI, so why shouldn't I keep driving on it?

    A bulge in the side of a cap is a gift that will help you avoid some nasty damage if you change the cap before it makes a nasty mess.
     
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  7. Commodore 64

    Commodore 64 Friend of Leo's

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    [​IMG]

    Supposed to be 220uF. So they measure pretty good. Would you put those back in?
     
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  8. jvin248

    jvin248 Poster Extraordinaire

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    .

    With all the 're-capping' going on tube amps ... Just buy new and replace those since you already have them out of the chassis. Caps only reliably last a decade or two of use inside the high voltages of tube amps. Remember that caps are not much more sophisticated than layering aluminum foil and wax paper from your kitchen and rolling that up into a tube so you can apply several hundred volts to it. Take one apart sometime to see.

    Solid state amps run much lower voltages and thus caps in those can last longer.

    .
     
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  9. 24 track

    24 track Doctor of Teleocity Silver Supporter

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    why wait for the carnage, the elecrtolyte will eat right through the PCB traces and really make a mess , and if the unit is apart already .....

    its kind of like dopping the transmision on your car , while its out replace the rear seal, because if you dont and the seal goes you have to pull the tranny to get at again.
     
  10. KyAnne

    KyAnne Tele-Afflicted

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    No. Replace it.
     
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  11. galaxiex

    galaxiex Tele-Holic Silver Supporter

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    That would be the front seal...

    ;)
     
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  12. DavidP

    DavidP Friend of Leo's

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    ... as others have said, replace now! You have a ticking time bomb there...
     
  13. galaxiex

    galaxiex Tele-Holic Silver Supporter

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    Wanna risk it? ;)

    [​IMG]
     
  14. 24 track

    24 track Doctor of Teleocity Silver Supporter

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    lol now you know why I work on gear not cars......LOL:lol::lol::lol::lol::lol::lol:

    thanks, but the point is the same!
     
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  15. 24 track

    24 track Doctor of Teleocity Silver Supporter

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    that cant be fixed, it will need an exorcism may be on multiple layers!
     
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  16. galaxiex

    galaxiex Tele-Holic Silver Supporter

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    Better yet...

    [​IMG]
     
  17. Blrfl

    Blrfl Tele-Meister

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    Electrolyte is like capacitor blood. If it ain't in there, it ain't gonna capicitate.*



    *Yes, I made that word up.
     
  18. peteb

    peteb Friend of Leo's

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    the problem with testing the cap is that it is probably not tested at full operating voltage.



    by the way, what voltage does the cap see? and what does the cap do?




    some are non critical and others are
     
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  19. galaxiex

    galaxiex Tele-Holic Silver Supporter

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    This ^^^^

    To properly test high voltage rated caps.... you need to test them at.... wait for it...

    High voltage...

    .. but not more voltage than the cap is rated for.

    You need something like this....

    100_2345.jpg

    Test for (electrical DC) leakage, cuz the cap MAY test ok for capacity and esr...

    but can still leak DC like a sieve.

    Regardless... if it's bulging/leaking/oozing... it needs to go...


    .
     
    Last edited: Apr 18, 2019
  20. schmee

    schmee Poster Extraordinaire

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    It can test fine, but still may cause noise etc and of course fail at the wrong time.
     
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