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LCD-TV repair

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    #61
    Re: LCD-TV repair

    Originally posted by PowerAmpFreak View Post
    The panel has two HV wires, each on either side of the panel. I believe there are several CCFL or EEFL's connected in parallell, so why shouldn't a few light if one or more were bad? Or their wires were loose.
    It looks like one of the inputs has been disconnected so none of the lamps has contact with the HV supply.
    By the way, is it possible to make a capacitance measurement across the lamps?

    After the easter holiday I'll try to take some close pictures of the panel assembly and see if any of you might have a good idea how to get into the lamp compartment.
    Think of it this way - capacitance is directly proportional to the overlapped area of the plates and inversely proportional to the distance between the plates. In my misspent youth I remember unwrapping paper caps - the layers were many feet long. In most capacitors the spacing is measured in thousandths of an inch. How much capacitance is there between 2 pinheads more than a foot apart?

    PlainBill
    For a number of reasons, both health and personal, I will no longer be active on this board. Any PMs asking for assistance will be ignored.

    Never be afraid to try something new. Remember, amateurs built the ark. Professionals built the Titanic.

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      #62
      Re: LCD-TV repair

      Originally posted by PlainBill View Post
      Think of it this way - capacitance is directly proportional to the overlapped area of the plates and inversely proportional to the distance between the plates. In my misspent youth I remember unwrapping paper caps - the layers were many feet long. In most capacitors the spacing is measured in thousandths of an inch. How much capacitance is there between 2 pinheads more than a foot apart?

      PlainBill
      Ok, I get it
      I think about building a small HV generator for CCFL testing purposes, what is the recommended operating voltage of a CCFL? And how much juice do I need to actually see something light up?

      Comment

        #63
        Re: LCD-TV repair

        Originally posted by PowerAmpFreak View Post
        Ok, I get it
        I think about building a small HV generator for CCFL testing purposes, what is the recommended operating voltage of a CCFL? And how much juice do I need to actually see something light up?
        Digikey lists a JKL BF24438-33B, which ignites at 1400 volts and operates at 835 Volts, 5 mA. The 2500 volts you saw should be enough to get the CCFLs to ignite.

        PlainBill
        For a number of reasons, both health and personal, I will no longer be active on this board. Any PMs asking for assistance will be ignored.

        Never be afraid to try something new. Remember, amateurs built the ark. Professionals built the Titanic.

        Comment

          #64
          Re: LCD-TV repair

          Originally posted by PlainBill View Post
          Digikey lists a JKL BF24438-33B, which ignites at 1400 volts and operates at 835 Volts, 5 mA. The 2500 volts you saw should be enough to get the CCFLs to ignite.

          PlainBill
          This will be simple enough to build, and be very handy when checking backlight panels in the future.

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