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remote control light

Discussion in 'Electronic Repair' started by Herb, May 2, 2007.

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  1. Herb

    Herb Guest

    (I'm having difficulty zeroing in on this in web/Usenet searches,
    because the common words lead to other subjects.)

    I have a Radio Shack 4-in-1 remote control for the tv, with a button
    that lights up the keys, for night use. However, there is something
    now wrong with it. Only the top keys were illuminated anymore.

    So I opened it up and lo and behold... there is no bulb that I could
    locate. Where does the light come from? It's a mystery. To top it off,
    the floppy soft-rubber piece that comprises the keys must have shifted
    or something, because now the pattern of light vs dark keys is all
    over the place.

    What key words can I use to search and read up on this lighting?
    Thanks.
     
  2. hr(bob)

    hr(bob) Guest

    Just play with it, there are Light emitting diodes that are used for
    illmination, they are about the size of the head of a pin for most of
    these applications. If you want to play fine, if you need a remote,
    its time to go to your nearest all-0purpose store and buy one for
    under $10.00 USA.

    H. R. (Bob) Hofmann
     
  3. Gary Tait

    Gary Tait Guest

    Its just LEDs. Small ones. Likey a resistor or a broken trace is the
    culprit.
     
  4. Herb

    Herb Guest

    well no, as I'd said, this is different. I experimented and see that
    it is some unusual device. There is a plastic film with wide, donut
    shaped white traces that light up. The white center dot makes the
    connection when a key is pressed, but the rings light up.
    http://img514.imageshack.us/img514/6969/remoteta0.jpg

    The links between rings don't seem to be broken. Maybe this material
    just wears out. Or, it's maybe a problem with contact. I tried it
    with the cover removed and see that the spots that light up are
    scattered.
     
  5. Gary Tait

    Gary Tait Guest

    It could be EL (Electro luminescent) material.
    Is there a small transformer on the board?

    The EL trace could be broken, which you may be able to repair with metallic
    ink.
     
  6. Like the watches?
     
  7. Herb

    Herb Guest

    Yes, there is a small transformer on the other side of the board.

    I noticed today, in a darker environment, that every ring has at
    least a speck that is lighting. So that new observation tends to go
    against the idea of a broken trace, I'd think.

    Using the term you've provided, I found a journal abstract which
    describes a type of failure:

    http://pubs.acs.org/cgi-bin/abstract.cgi/langd5/1998/14/i20/abs/la9709406.html

    "...defect on the indium tin oxide anode. These spherulites cause the
    device to delaminate, and this results in a decrease in the
    luminescence around the defect and, finally, the failure of the
    electroluminescent device."

    Degradation of Organic Electroluminescent Devices. Evidence for the
    Occurrence of Spherulitic Crystallization in the Hole Transport Layer

    Sounds unrepairable, I'd guess.
    And yes, I suppose it is just like the stuff on the watch I'm wearing
    - though much brighter and lots more area of it.

    They should make computer screens out of this stuff :)
     
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