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White "gloop" used to mount capacitors in.

Discussion in 'Repairing Electronics' started by Flyback, Apr 15, 2017.

  1. Flyback

    Flyback Well-Known Member

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    Hello,
    We have one of the subwoofer amps as in the attached video. If you look at 1:39 to 1:50 you can see the white “goo” at the bottom of the big electrolytic capacitors.
    On our board, this white goo has , in many places, gone dark brown and is crispy and brittle. Is this due to overheating due to a fault?
    When I scraped and picked the brittle brown stuff away off the board, there was a broken axial diode that had been buried in it. It’s broken up and the centre of its body has gone and we don’t know which part to replace it with.
    Ours is a Mordaunt-Short MS519 digital subwoofer, but it looks just like the one in this video.

    So is the "gloop" supposed to ever be dark bronw and brittle?

    see 1:39 to 1:50


    upload_2017-4-15_19-56-26.png [​IMG]
     
  2. Nigel Goodwin

    Nigel Goodwin Super Moderator Most Helpful Member

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    It goes that colour with age and heat.
     
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  3. Flyback

    Flyback Well-Known Member

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    Thanks, when you say "heat", you presumably mean 100degC plus?

    6:55 to 7:40 of this video, i just found, says that the glue gets conductive and corrosive when it goes crusty like ours has.
     
  4. dave

    Dave New Member

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  5. davenn

    davenn Active Member

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    I would hope long before that sort of extreme temperature was reached
     
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