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Fix water-submerged electronic remote ?

  1. May 15, 2013 #1
    Fix water-submerged electronic remote!!??!!

    I have an expensive (around $300) universal remote control that got water (I think? can't remember...some kind of beverage!) splashed on it about 2 years ago. When this happened, I immediately pulled the batteries and let it dry out for about a month. The next time I tried to turn it on, I put the batteries on and the thing beeped then just quit. Alas, I bought another one, but kept the old one hoping to get it fixed somehow/someday.

    About a year ago (1 year after the incident), I tried booting it up again. Same problem.

    Today, I decided to bust the thing open (it's built like an apple device, lots of hidden clips and stuff, practically no screws) and visually inspected it. After about 20-30 minutes of visual inspection I noticed a hard, clear coating at the base of all 4 capacitors. I tried picking at it, and with some effort it chipped off like plaque or something. The hard chips turned from clear to white as I was chipping. I was careful not to pull up or scratch any of the PCB conducting elements.

    I threw the thing back together, and it WOfRKS!!! What in the world was that stuf, and why is it fixed after I picked it away?!?!
     
  2. jcsd
  3. May 15, 2013 #2

    wukunlin

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    without seeing the pcb's and the gunk you picked away its hard to tell. I'm guess the gunk probably has enough conductivity to short circuit a bit or create enough parasitic effects to mess up some signals.
     
  4. May 15, 2013 #3
    But *if* this "depositing" actually was the perpetrator, then why did it only collect around the bases of the capacitors? If the hard deposits were part of the original design (pre-spillage), then what did the spilling do to these deposits to cause them to short/conduct/whatever-they-were-doing?
     
  5. May 15, 2013 #4

    Simon Bridge

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    1. the hard stuff was something causing the fault and it was part of the water that just happened to like the capacitors ... without knowing what it is there is no way to tell why.

    2. the hard stuff is incidental and the act of removing it also removed whatever was causing the fault - say a fine mineral salt deposit someplace that got shaken loose by the act of picking away the hard stuff.

    You can check by opening the new one and comparing.
     
  6. May 15, 2013 #5

    wukunlin

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    the stuff could also be stuff leaking out of your caps, assuming those are electrolytic capacitors
     
  7. May 16, 2013 #6
    I always thought that the onset of electrolytic capacitor leakage meant component failure, and therefore the remote wouldn't work at all. And secondly the "stuff" that comes out of caps is usually like a dark brown, right?

    I don't want to take the new one apart, as it never goes back together QUITE the same, and I'm rather obsessive about the feel of my buttons, etc.

    I I just thought there might have been some kind of known electro-chemical reaction between the caps' charge (possibly alternating?) and the liquid.

    Thanks for the posts guys!
     
  8. May 16, 2013 #7

    jim hardy

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    without hands-on it's all speculation.
    What you described sounds to me like "Conformal Coating", a varnish like stuff that they apply to boards to keep them from corroding .

    Your trouble was likely conductive stuff dissolved in the drink that got spilt. It gets under the buttons. Those "soft" buttons are almost non-conductive but not quite. When you push them they make contact with the circuit board, the pads for that contact are not conformal-coated..
    But it's not a zero ohm contact like a switch; the rubber switch pad is just enough less than infinity ohms that the board recognizes it as a pushed button.
    Sugar or coffee residue on the board from a spilt drink can look electrically much like a pushed button. It may take years to completely dry and become non-conductive enough to let the board work again.

    I got another six months out of my Dish TV remote by prying it apart, lifting the rubber button pad, cleaning both the pad and the circuit board with rubbing alcohol , then drying overnight on the fireplace. That advice I got here at PF.

    Good luck !
     
  9. May 18, 2013 #8

    Danger

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    Note that he said on the fireplace, not in it; that would be counterproductive.
     
  10. May 18, 2013 #9

    jim hardy

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    Well, actually that IS my last resort.
    When it gets to the point i'm investing too much time in some old piece of junk, I turn it into winter BTU's which both warms the house and spares me further distraction.
     
  11. May 18, 2013 #10

    Danger

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    :rofl:
     
  12. May 19, 2013 #11
    I used to work in quality where I tested products after accelerated life testing. One of the tests exposed the circuits to high humidity. When a unit failed, we checked the circuit board under a microscope for dendrites. These tiny metallic threads that grow between oppositely charged traces and are too thin to be seen without a microscope. They grow rapidly enough to be seen growing under the microscope. Sometimes when we couldn't find the dendrite we'd scrape between traces of opposite polarity and usually the problem disappeared.

    This is what I think happened to your control and in the process of all the scraping you did, you broke the dendrites.
     
    Last edited: May 19, 2013
  13. May 19, 2013 #12

    Simon Bridge

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    Option 2 post #4 looking good then?
    Actually this reminds me of when I was repairing old electronics - the fix was very often just to run a screwdriver between tracks on the circuit-board near components - particularly capacitors. Now I think I see why it worked.
     
  14. May 19, 2013 #13

    davenn

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    The "hard stuff" is also more likely to be some sort of adhesive
    often used to keep electro caps and other coponents in place
    to avoid them working loose with vibration and their solder joints becoming dry jointed

    Dave
     
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