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Brown stuff on my board...

Discussion in 'Electronic Basics' started by Andrew Howard, Oct 6, 2003.

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  1. I noticed one of the channels on my computer sound system was softer than
    the other. I narrowed it down to the amp, and promptly pulled it apart.
    One of the capacitors, maybe in the power supply section, seems to have
    'leaked'. It has a puddle of dried brown crap surrounding it ,and it covers
    one of the main transistors.
    What is the brown stuff, and would it cause problems?

    Andrew Howard
     
  2. In sequence: Leaked electrolyte, and yes, it probably could.

    My advice would be to first get the capacitor in question out of
    there. Next, thoroughly clean the board with 99% isopropyl alcohol (NOT
    the 70% or 91% stuff you see at drugstores -- use 99%, aka isopropanol,
    available at most electronic supply places including Fry's).

    Once the board is clean, replace the capacitor with either a high-
    quality electrolytic or a tantalum of similar capacitance and voltage.
    If you're not comfortable with, or lack the equipment for, proper
    soldering and desoldering, you should recruit assistance from an
    experienced technician. Perhaps from whatever ham radio club is local to
    you?

    Good luck.
     
  3. Will this affect any other parts on the board, or make the glue covered
    everywhere go crappy, etc?

    Do you think I will need to replace anything else?


    Thanks

    Andrew Howard
     

  4. Before doing what Anton Squeegee recommonds, I suggest making certain the
    brown stuff really is leaked electrolyte. Quite often brown glues are used
    to glue components down for the maufacturing process (makes it so they don't
    move around/fall out for soldering and handling). Usually the brown glues
    will be shiny and quite hard. If the capacitor really did leak the stuff,
    then most likely it will be buldging or otherwise appear quite deformed.
    Usually the electrolyte leaves behind a "corroded" appearance.
     
  5. Before doing what Anton Squeegee recommonds, I suggest making certain the
    There is glue on the board, it is stringy, light brown and shiny. The stuff
    I am talking about is a dark brown solid in a thin layer covering part of
    the board, centralised arouind the capacitor in question.

    About the cap, what should I look for, and what should I use to test it? I'm
    not sure wether I can get hold of a capacitance meter.

    Andrew Howard
     
  6. JeffM

    JeffM Guest

    Look for a bad seal / hole (may be very tiny) or for more electrolyte residue.
    Don't test it. If you suspect it--replace it (they aren't expensive).

    The one thing that Bruce left out is that these things are POLAR in nature;
    put the + of the new one where the + of the old one was.

    "Quando Omni Flunkus Moritati" == When all else fails, play dead.
     
  7. I'm going to replace it, but I would like to know some extra things before I
    do anything else. I wrote the questions in a different post, but I will
    repeat them here.

    Will cleaning it with the isopropanol stuff affect anything else on the
    board?

    and

    Should anything else need replacing?

    Thanks for the help so far.
    Andrew Howard
     
  8. JeffM

    JeffM Guest

    Will cleaning it with isopropanol affect anything else

    Unlikely. That's why that IT was suggested (comparatively weak solvent).
    If you have a white haze left after drying, clean that off with soap & water.

    Good question. Sometimes it's a process of elimination.
     

  9. I would probably use water to remove the electrolyte (use gloves, as
    there may be sodium hydroxide or similar nasties in it). Then either
    allow to air dry completely (!), or use isopropanol to remove the water.
    Instead of isopropanol, you can use IMS (industrial methylated spirit),
    which is cheaper and available in hardware stores. Beware of the fire
    hazard with both fluids.

    This procedure should be safe unless the board has components where the
    water can creep in and not come out again (like transformers).
     
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