LG Washing Machine Control Board Question

Discussion in 'General Electronics Chat' started by bwilliams60, Aug 5, 2015.

  1. bwilliams60

    Thread Starter Active Member

    Nov 18, 2012
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    I have this control board from an LG washing machine and the main fuse is open so I suspect there is a short in the power supply section of it as there is no power on the front panels when plugged in and turned on. My question is in regards to the epoxy and although I think I already know the answer, I will ask anyways. There is a rubbery coating that the whole board is immersed in. Has anybody ever successfully removed one of these boards, repaired it and returned it to it's former glory. If you have, how did you go about doing it. I would be surprised if anybody has done this but curiosity has gotten the best of me.

    Bill Phone 3 004_1280x919.jpg
     
  2. MaxHeadRoom

    Expert

    Jul 18, 2013
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    If the 'rubbery coating is 'Conformal Coating', there is special remover for this, it can then be re-coated after repair.
    Max.
     
  3. BR-549

    Well-Known Member

    Sep 22, 2013
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    Is it really rubbery? Can you get a meter probe thru it?

    Did it blow a replacement fuse?
     
  4. mcgyvr

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    Oct 15, 2009
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    Thats "technically" potting compound
     
  5. crutschow

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    Mar 14, 2008
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    "Technically", conformal coating and potting compound are usually two different materials.
    Conformal coating is generally just a thin layer covering the board and components.
    Potting compound is thicker and normally encases the whole circuit in a block of material.
     
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  6. bwilliams60

    Thread Starter Active Member

    Nov 18, 2012
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    This coating is rubbery and covers the entire board. It's like they placed the board in a large plastic container, and then poured a compound or coating to a depth of about 1/2" to cover the board. The fuse is not a replacement fuse and is soldered into the board. Very nice looking job. Almost hate to cut into it :).
    If this coating can be removed, how toxic is it?
     
  7. #12

    Expert

    Nov 30, 2010
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    I wouldn't worry about that. Then again, I wouldn't eat the coating either. ;)

    As for the fuse? Look to the motor or the motor drivers. Is that merely a relay? Mine uses mosfets for forward, reverse, and rate control. There is also a water pump and some water valves. The water pump might short but the water valves usually go bad in the "open" condition.
     
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  8. mcgyvr

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    Yes.. I'm aware.. Thats potting compound as shown in the image.. Its "potting" the whole board inside the plastic housing. Hence my answer ;)
     
  9. MaxHeadRoom

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    Unusual for C.C. to be 1/2" thick?
    It is not toxic once set, unless you light it!
    The remover gives off a little fumes or odour.
    You would not need to remove it all though.
    Max.
     
  10. mcgyvr

    AAC Fanatic!

    Oct 15, 2009
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    because its not CC.. :D

    acetone "may" work on epoxy based potting compound and sometimes "silicone" caulk remover from the hardware store will work with the silicone based kind.. or just picking/cutting at it with a knife/chisel..
     
  11. MaxHeadRoom

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    I only see C.C. in the JPG?
    No epoxy potting 'covering the whole board' to a depthe of 1/2"?
    Max.
     
  12. mcgyvr

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    Then either you are blind or thinking about the other topic that has CC on it.. :cool:
    This is clearly potting compound..
    Notice the "yellow" going all the way past the board edges and touching the white plastic enclosure..
    I wouldn't say its 1/2" deep though.. Maybe 1/4" but hard to tell from straight on
     
  13. KeepItSimpleStupid

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    Mar 4, 2014
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  14. MaxHeadRoom

    Expert

    Jul 18, 2013
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    On the contrary:rolleyes:, I do not see components that are typically 1/4" - 1/2" in height including small connectors that are submerged in compound.
    Max.
     
  15. #12

    Expert

    Nov 30, 2010
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    C'mon guys. It doesn't matter what kind of coating you call it. Just get a dental pick and start picking at it. The fuse will be accessible in a few minutes and the quest for the culprit can continue.
     
  16. bwilliams60

    Thread Starter Active Member

    Nov 18, 2012
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    Wow, sparks are flying....just a question. No need for arguing. I measured the thickness of this compound by sticking a paper clip in and marking it with a marker. It is indeed 1/2 " deep. If pictures are necessary, I can post them however it doesn't relate to my question. As I said, I believe it is poured into the container and forms a bond between container and bond on the trace side. I could pick away at it but I think I need to remove the board from the container to perform any repairs. I'm sure it is cheaper to buy the board but where is the adventure in that? Any ideas now? Play nice.
     
  17. mcgyvr

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    Its potting compound..
    Its silicone based as you can stick a paper clip through it where an epoxy based compound is typically "harder"..
    There is really no good/proven silicone potting compound remover that I'm aware of.. Like I said above you could "try" silicone caulk remover to attempt to "soften" it up some more but short of picking/cutting/scrapping it off with a knife/pick your are better off just replacing the whole part if you know something on the board is damaged.. Its not meant to be removed... It SUCKS to attempt to replace an old capacitor,etc.. in anything thats potted..
     
  18. mcgyvr

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    Yep just not safe to fish during curing. (up to 1 week..typically 48 or so hours)
    I've fixed/built aquariums/sumps with regular GE type 1 or Momentive RTV many a times..
     
  19. #12

    Expert

    Nov 30, 2010
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    With the back side of the board flooded in compound, you are in for a job I wouldn't want. The way I see it, you will have to grind off one whole side or end of the container and slip a knife in to get the board loose. Meanwhile, you're fighting the front prongs that hold the board down. Better slice those off, too.

    Eventually you arrive with a messy board that needs cleaning near the fuse.

    This makes me think about burrowing down to the fuse from the front and soldering a new fuse on to its ends. You still have to find the REAL problem. Fuses don't commit suicide without a reason. Finally, send a box of poison candy to the engineer that designed a machine with a fuse intended to cost you a whole circuit board when a motor shorts out. :mad:
     
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  20. bwilliams60

    Thread Starter Active Member

    Nov 18, 2012
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    I think I am at the end of the road. I have better things to do than dig through this s#@t to get to a fuse and who knows what else. If it wasn't so time consuming, I would give it a go but this looks like hours of my live that I will not get back. I think I will go read about potting and conformal coating. Sounds like an explosive subject :).
     
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