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Unusual zapper failure mechanism

Discussion in 'Electronic Repair' started by N_Cook, Jul 17, 2013.

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  1. N_Cook

    N_Cook Guest

    Plasticizer or something leaching out of the flexible membrane, at the
    edge, dissolving the green pcb lacquer coating and etching lines into
    the pcb traces. The one that failed was actually at this line through a
    test pad circle, rather than just the width of a trace
  2. Jeroni Paul

    Jeroni Paul Guest

    The plastic membrane seems to leave this oil slowly. I have so far not seenany secondary effect caused by this oil, it appears to be non conductive, non corrosive and it allows the contact of conductive pads without problems.. When I have to repair a remote I clean this oil but after some time of use it forms again near the most used buttons.

    The conductive black rubber sooner or later wears out. Cleaning the surfacesometimes works but not for long. Time ago I used conductive paint but it does not last either. I found it difficult to paste conductive foil, it canfall easily and keep the button permanently pressed.
    So for a lasting repair I use a needle to create a small hole across the rubber under the conductive surface, it is surprisingly easy to puncture. Then I run a very fine copper wire through this hole and bend the ends so theylay on the failing conductive pad. It lasts forever and works great.
  3. N_Cook

    N_Cook Guest

    It naybe an abrasive process. Although the buttons nearest this edge are
    never used, perhaps the membrane does move each time of usage. The
    "etched" line is very precisely along the line of the edge of the
    membrane. No drink ever spilt on it, very hot environmentally at the
    moment, maybe connected with the failure
  4. N_Cook

    N_Cook Guest

    Next time with a pad failure I'll try your "sewing" a loop of copper
    wire through the pad. Concerned about local pressure of the wire cutting
    into the pcb conductive traces I would flatten the pad part of the wire
    in some pliers with a washer "depth-stop"
  5. Jeroni Paul

    Jeroni Paul Guest

    Before you flatten test the button by placing the rubber exactly the same position as assembled. Sometimes slight adjustments are necessary to the wire bending or position to match the PCB traces. Some cheap remotes do not perfectly align conductive pads and board traces, so placing the wire centered does not always work.

    Anyway if the wire is fine enough the rubber accomodates it easily.
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