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Req: Help with a 19" TV purity problem

Discussion in 'Electronic Repair' started by Tim, Jun 2, 2008.

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  1. Tim

    Tim Guest

    OK, this is a problem with a 19" Citizen TV. It is just over a year old.

    If the set is put on a stand that has a metal object (like a Satellite
    Receiver on a shelf) mounted within 8 inches below the set, the pic has
    a very noticeable purity problem all the way across the bottom and about
    1/2 way up each side. If I raise the set up, the purity problem will
    diminish, but even up at 8" away from the console stand, it still has
    slight purity issues.

    Raising the set up on boxes is problematic, as the space is very
    limited. I would like to shield whatever it is. I am not sure if it is a
    reflection from the set or radiated magnetic fields from the equipment
    below.

    The console is in a travel trailer, so I cannot move everything away
    from the tv, as most of the electronics are in this one console, with
    the TV on top of it.

    Any helpful suggestions are appreciated.

    Thanks,

    - Tim -
    --
     
  2. bz

    bz Guest

    I assume that this is a CRT tv, not a LCD or plasma tv.

    Sounds like the 'metal object' contains a strong magnet or has been
    magnetized.
    I have some magnets that will effect a CRT from over 2 feet away.

    A transformer can also radiate a[n AC] magnetic field that disrupts nearby
    devices.

    If you can find the source of the magnetic field and move THAT away from
    the TV, it should fix the problem.

    It is possible that putting the set in place and then 'degaussing'
    everything in the vicinity will 'fix' the problem.

    Does your Satellite receiver have a built in hard drive for recording
    programs? It is possible that the drive is 'leaking' a strong magnetic
    field [but most hard drives confine the field very well]






    --
    bz 73 de N5BZ k

    please pardon my infinite ignorance, the set-of-things-I-do-not-know is an
    infinite set.

    remove ch100-5 to avoid spam trap
     
  3. Tim

    Tim Guest

    Yes the TV is CRT, and no, the receiver does not have a HD in it, nor
    does it have a large transformer. The purity problem is static, that is
    it does not change colour, so I don't think it's a transformer, as that
    would cause a rainbow effect.

    Maybe I'll try rearranging the "stack" of components to see if one of
    the other devices cause less magnetic radiation, or reflection if that's
    the case.

    It would be nice if this set had a manual degaussing option, but alas it
    doesn't. I don't even hear the coils buzz when the set comes on, but
    there are no other purity issues, so they must be functional. I'll take
    my tape eraser down with me, and try that to see if the problem returns
    after zapping the screen.

    Thanks,

    - Tim -
     
  4. bz

    bz Guest

    Lacking an eraser, if you can hang a magnet on a string so that you can
    spin it, you can sometime degauss with that.

    I had a nice heavy magnet from an old radar magnetron that had a hole in
    just the right spot.
    I had a loop of copper wire threaded through the hole and hung the
    contraption from a piece of string.
    I would wind it up good and let it spin, slowly moving it away from the
    monitor.
    Did a good job of degaussing.

    Sometimes, for a joke, I would spin it on the other side of a wall, near
    someones monitor.
    They would come running out of their office "something strange is happening
    to my monitor. The picture is wobbling all over the place and changing
    colors!" :)


    --
    bz 73 de N5BZ k

    please pardon my infinite ignorance, the set-of-things-I-do-not-know is an
    infinite set.

    remove ch100-5 to avoid spam trap
     
  5. hr(bob)

    hr(bob) Guest

    The OP did not say if the stand was metal or not. If it is metal, that
    may be adding to the problem. The spinning magnet to degauss is an
    old trick that works well as long as it is spinning rapidly compared
    to how fast you are moving awa from the set.
     
  6. Tim

    Tim Guest

    The stand is wooden. The shelf is merely a 3/4" press board with
    arborite on the top. The lower shelf has 3 devices stacked up on it,
    with the satellite receiver on the top of the pile, and about 1" away
    from the bottom of the shelf the tv sets on. The whole thing is only
    about 21" wide and about 3 feet tall.

    - Tim -
     

  7. try putting a sheild between, see what you can find, a sheet of
    alunimum might be enough. sheet of tin that is grounded might be even
    better.
    I have screwed up a couple of TV's by playing with magnets near them,
    never had much success with degaussing them that way but I am sure it
    is possible.

    Phil
     
  8. Tim

    Tim Guest

    In the past I have tried using Aluminum to shield against RF, but
    haven't had much success with that. I will try a grounded sheet though,
    maybe that will work better. The worse case is that it makes the problem
    even worse, but it will go away the next start up.

    - Tim -
     
  9. bz

    bz Guest

     
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