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transistor failures

Discussion in 'Electronic Basics' started by thomas, Aug 6, 2004.

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  1. thomas

    thomas Guest

    We have a remote outdoor sensor that is prone to failure (nearby lightning
    we suspect). It is only a couple transistors (2N3904, 2N3906), a couple
    100V electrolytic and ceramic caps, a1N4148 and a few resistors.
    Unfortunately they are potted so I can't do a post-mortum. I can't use TVS
    or similar that shorts when failed because it will load the controller,
    which I can't modify.

    Are there tougher transistors or other components that we can use?
     
  2. John Schuch1

    John Schuch1 Guest

    What is the sensor sensing?
    How long is the wire run from the sensor to the control?
    How is it actually run?
    What kind of wire is used?

    John
     
  3. thomas

    thomas Guest

    Induction sensor
    The Belden 8723 wire is 2TP 22AWG and a run can 100+ feet long, in metal
    conduit.
    12V is run on one pair with signal on the other.
     
  4. You can put reverse biased diodes across some points to clamp the
    voltages to the supply and ground. Zeners also might help in certain
    places. When all else fails, use sockets so that you can replace the
    parts that burn out. ;-)

    And make sure that the diodes can handle high enough current to not burn
    out, too.
     
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