help with water damage

Discussion in 'General Electronics Chat' started by dontknowjack, Jan 24, 2014.

  1. dontknowjack

    Thread Starter New Member

    Nov 21, 2013
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    attached are photos of some water damage on a circuit. it is from a lighting board for a special sensory device from a school for children with Cerebral Palsy. I have cleaned the circuit board and removed the corrosion. ohm tested all the circuits I could find that were corroded. found one with an open circuit. I am not familiar with the best way to repair this. I am looking for as cheap as possible since I am doing this as a favor to the school, but I also want it to be right. could I run a wire from pin to pin? also there is a chip on the opposite side of the board I'm wondering if that chip could have been damaged (short circuit) by the water also. there was no corrosion on the side with the chip but could it have been damaged by the short on the other side? (you can see were the chip was in the overall photo that it is missing on the upper left side)any way to check this? I have a multi meter and some common knowledge of circuits. feel free to ask questions or offer advice.
     
  2. takao21203

    Distinguished Member

    Apr 28, 2012
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    WD40 is your friend here.

    What in your opinion prohibits to use a patchwire for an open PCB track?
     
  3. dontknowjack

    Thread Starter New Member

    Nov 21, 2013
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    by patch wire do you mean running a wire from pin to pin? if so nothing that i can think of. just didn't know if there was a better way.
     
  4. takao21203

    Distinguished Member

    Apr 28, 2012
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    use a thin wire wrap wire, bend it so it follows the track closely, and then secure it with superglue.

    Superglue just applied on the side of the wire will harden out sufficiently to secure the wire.

    Use a single core bell wire if you dont have wire wrap wire available, or magnet wire from a coil/transformer.
     
  5. dontknowjack

    Thread Starter New Member

    Nov 21, 2013
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    this is what i did to repair it just to test the system to see if it will work with that circuit fixed. but i don't know if this is good enough for a long term repair
     
  6. MrChips

    Moderator

    Oct 2, 2009
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    Use wire-wrap wire and keep it short and tidy.

    [​IMG]


    And after you have repaired the board and tested that it is functional, coat the board with conformal coating to avoid water damage in future.

    Do it right, do it once.
     
  7. dontknowjack

    Thread Starter New Member

    Nov 21, 2013
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    i intend on completely moving the board to a new and safer location.... but i will also coat it
     
  8. studiot

    AAC Fanatic!

    Nov 9, 2007
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    Circuit boards are often washed (in a dishwasher) so water does not always damage circuitry.
    The important thing is to let things dry out thoroughly before refit.

    We have had a thread about this before.

    In your case your board is basically sound, but seems to have suffered some corrosion that may be a combination of water and some other chemicals, heat and time.
    So repair is practicable.

    After repair I suggest you coat everything in several coats of clear spray varnish before refit.
    If possible also use a potting compound.
     
    Last edited: Jan 24, 2014
  9. dontknowjack

    Thread Starter New Member

    Nov 21, 2013
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    if I shorten the wire I am using and glue it down in place would that be a big enough wire or should I use a bigger gauge?
     
  10. MrChips

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    Oct 2, 2009
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    In this case gauge is not particularly important. Wire-wrap wire is 30AWG.
    Does that wire you're using have insulating enamel coating?
     
  11. dontknowjack

    Thread Starter New Member

    Nov 21, 2013
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    No it doesn't which is why I know its only temporary. can i get wire-wrap from radio shack?
     
  12. MrChips

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    Oct 2, 2009
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  13. ian field

    Distinguished Member

    Oct 27, 2012
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    If there isn't any wire-wrap to hand, a single strand from stranded hookup wire is more than adequate between logic chips and maybe the relay coils too. Using stranded wire as is, is risky because of the possibilities of stray strands.

    In the UK; the 4 circuit telephone wire they use inside the house is 4 solid wires, a fair bit thicker than strands from hookup wire, ideal for repairing the heavier supply rail traces.

    With the thicker solid wires, it helps to stretch it straight before forming it to follow intricate tracks.
     
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