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Never heard of this

Discussion in 'Misc Electronics' started by [email protected], Oct 23, 2005.

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  1. Guest

    I'd guess you guys'd know about it, but it seems
    a little strange to me. Friday evening we had a
    lightning strike just outside our place. It knocked
    out our wired phone service, cause a water pipe
    underground to rupture, but the weirdest thing
    is that it damaged (I guess) all the CRT screens
    in the house (TVs and computer monitor). The
    phosphors were affected. We've got kind of
    a rainbow across the screens now, though one
    of the TVs seems to have "healed" itself a little
    since then. None of the electronics were "fried."
    Would this be the electric field around bolt
    that did this, since the no surge apparently came
    through out power lines? (That said, did current
    did wink out for a couple of seconds after the strike.)
    Thanks.
     
  2. James Sweet

    James Sweet Guest


    It's very common, the shadow mask has become magnetized by the intense
    magnetic field created by the nearby lightning strike. Normally the
    internal degaussing coil is enough to fix it and the rainbows will go
    away on their own after turning the set on from cold a few times. If it
    persists then you'll have to use an external degaussing coil or bulk
    tape eraser to do the job.
     
  3. Take the wall plug out before you go to bed, and the next morning plug it in
    and everything should be just fine :)

    (a special resistor inside has to cool down...)
     
  4. James Sweet

    James Sweet Guest

    It's a PTC thermister, and no need to unplug it, just turn the set off
    and let it cool for a half hour or so.
     
  5. Jamie

    Jamie Guest

    don't worry, it will go away!, just turn off the
    tv and let it cool down and then turn it back on.
    do this a few times so that the coil can degauss the
    screen that is around the tube..
     
  6. Don Stauffer

    Don Stauffer Guest


    I was working with 3M one time on a magnetic traffic marking tape. They
    really got a lot of magnetic material into the tape. One of the
    engineers was demonstrating by running a piece around a computer (CRT)
    screen, and permanently hosed up the screen. He had to go out and buy a
    demagnetizer/degausser from Radio Shack to fix the guy's monitor :)
     
  7. Don Stauffer

    Don Stauffer Guest


    There is a limit to the strength of the built-in degaussers, though. It
    may indeed take an outboard degausser if the mask was magnetized
    strongly enough.
     
  8. Jasen Betts

    Jasen Betts Guest

    ["Followup-To:" header set to sci.electronics.misc.]
    the electric current in the strike causes a magnetic pulse which
    magnetises the iron/steel parts in the monitors, the magnetic field caused
    by these parts distorts the piicture and particularly the colours.

    as you have seen it does heal slowly, also turning the device off and on
    or activating the "degauss" feature will usually fix this problem.
    in bad cases it may need to be repeated a few times.

    Bye.
    Jasen
     
  9. clifto

    clifto Guest

    The weirdest one I ever saw had perfect purity -- red OR green OR blue
    OR monochrome -- but had the funkiest colors you could imagine. I
    puzzled over that set for half an hour before calling in to the chief
    tech for help. He insisted on my degaussing it despite the perfect
    purity, and of course that fixed it. It was only then that I realized
    there was a storm the previous night, and asked the lady of the house
    if lightning had hit nearby; she pointed to a blackened spot on the
    concrete not fifty feet from the house and claimed a direct hit there.
     
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