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Partly wet circuit board

Discussion in 'Troubleshooting and Repair' started by JustinN, Oct 28, 2016.

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  1. JustinN

    JustinN

    6
    1
    Oct 28, 2016
    I'm a complete newb in the area although I have saved a number of people's iPhone logic boards after being submerged in saltwater a few times.

    I have a deer feeder we use onour property to feed the local deer. I went to refeed and do regular maintenance and I noticed the weather protection piece was filled with water (no telling how long). To my surprise, the battery connections were a little bad, but after a little tweaking, it worked fine. All the buttons worked and i was able to reprogram the timers. I walked out a week later and noticed the timer had gone off. It showed the time on the lcd, but the program button wouldn't work while the + and - as well as the test button would work. I assume the water level didn't go higher than the program button.

    I took it apart and found corrosion on the back of test button. I attempted to clean it with isopropyl along with a toothbrush and I had no results. While being disconnected from the battery the lcd still showerd power but i assume the capacitor just kept holding the charge. I removed the circuit board from the panel order to see if there was corrision on the front. I had to remove the brown board (pins connected to lcd) in order to get a screw out and pull it from the panel. Once i did this the lcd shut off. I cleaned the corosion, placed it back together and i can not get anything to show on the LCD. Much less get the buttons to work like the test feature.

    Any Ideas?

    Any help would be appreciated.
     

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  2. Bluejets

    Bluejets

    4,263
    907
    Oct 5, 2014
    The buttons (rubber pads) have a conductive coating which you have probably scrubbed off. Parts of the lcd also have to be handled carefully as well. All parts of the lcd have to be exactly aligned.
     
  3. JustinN

    JustinN

    6
    1
    Oct 28, 2016

    Thanks for the speedy reply. That may be the case as I lightly hit the rubber buttons as well but I think I hit all of them.

    I see what you're saying on the LCD, but as you can tell it only has once spot it can sit with no wiggle room and the the board screws into the exact same place.

    What do you suggest
     

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  4. davenn

    davenn Moderator

    13,669
    1,891
    Sep 5, 2009
    that's cool :) just give each side of that rubber zebra strip a wipe with a cotton bud and some meths or isopropyl alchol
     
  5. JustinN

    JustinN

    6
    1
    Oct 28, 2016
    Looks like that helped! Just a little more pressure and the iso
     
    davenn likes this.
  6. JustinN

    JustinN

    6
    1
    Oct 28, 2016
    Well it looks like davenns suggestion helped me with the LCD, but now I'm back to the original problem of the program button. What else can I do? What about blue jets suggestion for conductive coating? I feel like I'm so close... I attempted to heat the pcb to 150 to make sure there was no water.


    I tried uploading a vid of the board working but it's not an option.

    If the board will not work can we hack the motor? I just need different times of the day to trigger the feeder to run for a certain a punt of seconds.
     

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  7. davenn

    davenn Moderator

    13,669
    1,891
    Sep 5, 2009
    I have had success with that
    I have also gone to the trouble of slicing the conductive tip off another key pad ... some old no longer used remote etc ... and sliced off the faulty pad and supaglued on the replacement pad
    that has also worked for me in the past
     
  8. JustinN

    JustinN

    6
    1
    Oct 28, 2016
    Where can i get conductive coating? lol
     
  9. HellasTechn

    HellasTechn

    1,542
    214
    Apr 14, 2013
    You can try this to check if the rubber pads are bad. use a flat head test screw driver and short the leads on pcb (under the rubber pads) if that triggers a responce on the circuit that means your pads are bad. If not...

    If your pads are indeed bad then you can eather cut them out and glue on some other rubber pads from say an old remote control, as suggested above or you can try what i do most of the times:

    I remove the rubber pad, then on the pcb i solder a miniature button switch carefully not to short the pcb leads.

    like in the picture here of my tv remote control. In my case both the rubber pad and the pcb had conductive coating, So i scratched away the coating on the PCB, fountd the connection points and soldered the button directly on them.

    P.S.
    Note that i had to cut out the whole rubber pad because after closing the plastic case it would keep my button pressed at all times.
     

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    chopnhack likes this.
  10. JustinN

    JustinN

    6
    1
    Oct 28, 2016
    As i mentioned, complete newb. So are you suggesting I hook everything up and then just hit the program button with a flathead? I'm not exactly sure how I'd short it
     
  11. HellasTechn

    HellasTechn

    1,542
    214
    Apr 14, 2013
    Yes, exactly.
    In picture 1 i have put "prog" in a red box where with your flathead test screw driver the Yellow lines should touch the green lines.
    I strongly recommend that you use a test screw driver because their nose has no coating that might act as insulation.
     

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    Last edited: Oct 30, 2016
  12. HellasTechn

    HellasTechn

    1,542
    214
    Apr 14, 2013
    I have noticed signs of corrosion on your pcb. I have marked them with RED arrows.
    To check if pcb is ok at that point you should use a Digital Multimeter set to continuity from point A to point B and from point A to point C the multimeter should "beep" indicating continuity, if not then you will need to wire theese points before buttons can work again.
     

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    chopnhack likes this.
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