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odd purity problems

Discussion in 'Electronic Repair' started by William Sommerwerck, Mar 22, 2009.

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  1. One of the great things about flat-panel displays is that they don't need
    purity or convergence adjustments. I'd like to tell you about two purity
    problems I've had with my own equipment (hmmm...) and get your views on the

    Case 1: When I purchased a Toshiba CZ-3299K IDTV, the set arrived with a
    severe impurity splotch at the lower-right corner. This appeared to have
    been caused by a shock to the shadow mask during shipping. I put up with it,
    until I moved to a condo in 1998. Lo and behold, the splotch vanished! The
    "shaking about" during the move must have de-warped the shadow mask, or
    perhaps knocked it back into place.

    Case 2: About five years ago, someone in this group had a question about
    removing impurities. In my desire to demonstrate that there was no degree of
    magnetization that could not be removed, * I held a bulk-tape eraser
    designed for metal-particle tape near the lower-right of my 400-series Sony
    WEGA IDTV, and shut it off. Naturally, the aperture grille was badly
    magnetized. Much to my dismay, I could not completely remove the impurity!

    It persisted, in varying degrees, until yesterday. I had the Magnolia guys
    move the set into the bedroom -- and it was gone! (I should note that the
    set now sits at 90 degrees with respect to its initial position. But it's
    unlikely that the original impurity had anything to do with the Earth's
    field. There was no impurity before I'd "zapped" the set.)

    Thoughts, anyone?

    * This is at least theoretically true, as there is a limit to how much any
    magnetic substance can be magnetized, and it cannot be greater than the
    magnetizing force. (I think.) (Please note that I'm talking about magnets,
    not solenoids.)
  2. Guest

    I don't know about the Toshiba but on Sony I had a broadcast BVM-1910
    that got the aperture grille wires criss-crossed from a hand held
    degaussing coil. On a tour at the San Diego Sony plant in '86 I saw a
    guy whose job it was to hit each new CRT (hanging conveyor) in the
    face with a rubber mallet. 3 or 4 smacks later, the monitor was fine
    again. Sometime percussive maintenance works.

  3. ...I had a broadcast BVM-1910 that got the aperture grille wires
    The thought of "whacking" the faceplate never crossed my mind. The small
    vibrations of moving the set and laying it down on another stand must have
    been enough to "detangle" the wires.
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