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Another Problem TV Thrown My Way - Sony KV27S42 - Purity Problems

Discussion in 'Electronic Repair' started by Tim, May 11, 2007.

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  1. Tim

    Tim Guest

    This one was dropped on the bottom left corner by the looks of the
    cracks in the case. Now it has bad purity down the left side, and the
    bottom right corner. I have found some info on the net here;

    http://videotech.lesterville.com/sony.htm

    I thought I would check here to see if there are any alternatives to
    trying magnets etc to get the purity back. I seem to recall that the
    rings on the neck of the CRT used to be used for purity too, but these
    ones have not moved.

    Thanks,

    - Tim -
     
  2. Meat Plow

    Meat Plow Guest

    If it was dropped the shadow mask inside the tube has shifted and you need
    magnets.

    --
    #1 Offishul Ruiner of Usenet, March 2007
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    #1 Bartlo Pset, March 13-24 2007
    #10 Most hated Usenetizen of all time
    Pierre Salinger Memorial Hook, Line & Sinker, June 2004
    COOSN-266-06-25794
     
  3. Tim

    Tim Guest

    I thought it would be something like that. I experimented with my
    magnetic screwdriver, and I was able to almost eliminate most of the
    problem on the left side while it was near the back of the CRT, so maybe
    I'll experiment some more with magnets.

    It probably doesn't matter at this point, but I had the symptoms
    reversed. It was dropped on the right corner and the purity problem was
    mostly down the left side.

    Thanks for the info.

    - Tim -
     
  4. hr(bob)

    hr(bob) Guest

    I used to cement small magnets to the picture tube glass bell using
    silicon rubber.

    H. R.(Bob) Hofmann
     
  5. Tim

    Tim Guest

    Just an update...

    I have 6 magnets on the CRT right now, and the problem is almost gone. I
    just have to remove one small area at the top and it will be good as new
    again. It's hard to imagine that sticking magnets on the CRT would
    resolve the issue so well, but hey the results prove the theory.

    I'll get at it again tomorrow.

    Thanks to Meat Plow for the heads up...

    - Tim -
     
  6. Tim

    Tim Guest

    I used double sided foam tape after cleaning the glass. I saw that there
    was a small circular one already attached that way, so I copied the
    method. If they fall off, I'll use your silicon rubber idea.

    Thanks,

    - Tim -
     
  7. JANA

    JANA Guest

    In the Sony sets, the purity magnets should be very well glued in to place.
    Going from experience, the shadowmask in the CRT is probably damaged. These
    sets are so sensitive, that a small drop can damage the shadow mask.

    --

    JANA
    _____


    This one was dropped on the bottom left corner by the looks of the
    cracks in the case. Now it has bad purity down the left side, and the
    bottom right corner. I have found some info on the net here;

    http://videotech.lesterville.com/sony.htm

    I thought I would check here to see if there are any alternatives to
    trying magnets etc to get the purity back. I seem to recall that the
    rings on the neck of the CRT used to be used for purity too, but these
    ones have not moved.

    Thanks,

    - Tim -
     
  8. Tim

    Tim Guest

    OK I have the purity fixed up perfectly now. I need to adjust the
    rotation (tilt) of the pic tho, it is off by about 3/8". Does this set
    have that adjustment in a service menu? I would need to know how to
    activate that menu. I know I could open the set up again and adjust the
    yoke manually, but I like to try the electronic tilt if possible.

    Thanks,

    - Tim -
     
  9. Jeroni Paul

    Jeroni Paul Guest

    Did you try to degauss the tube (a power cycle) after placing the
    magnets?
    Most of the times it will cancel their effect. On a similar problem
    the only fix I found was to unplug the degausser once the CRT was left
    properly magnetized and installed at its definitive place. A big
    speaker magnet works pretty well at magnetizing CRTs.
     
  10. Tim

    Tim Guest

    The set has been cycled many times since I placed the magnets on the
    back bell of the tube. I did get some Silicon II to attach them with
    tho, as I decided the double sided tape may let go after a bit. It still
    looks great, just tilted now.

    It was my understanding that trying to demagnetize the CRT is not
    advisable because it will destroy the conditioning of the tube and it
    will never return to proper purity again. And it really has come back
    nicely, so I don't see the need to try and manually degauss the CRT.
     
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