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Zenith 25" color TV SM2568S CRT board color adjustments

Discussion in 'Electronic Repair' started by Jacques Carrier, Sep 27, 2004.

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  1. Gretings from Montreal to all fellow techs,

    I fixed the vertical problem on this nice 25" 1994 color TV (bad solders).
    I would like to know how to properly adjust the 3 potentiometers
    located on the CRT board.I did not find any grey scale pots ??
    Maybe the CRT is getting old ......The colors are not crisp enough
    and there is a light green hue.
    If you have a service manual please get in touch with me.

    Many thanks for your help,


    Jacques
     
  2. Andy Cuffe

    Andy Cuffe Guest

    Those 3 pots on the CRT board are for grey scale. They adjust the red
    green and blue bias. There are no drive controls on that set. Being
    a 1994 Zenith you probably won't be able to get a good picture. Those
    sets have CRT which go weak within a couple of years.
    Andy Cuffe
     
  3. Asimov

    Asimov Guest

    "Jacques Carrier" bravely wrote to "All" (27 Sep 04 05:44:16)
    --- on the heady topic of "Zenith 25" color TV SM2568S CRT board
    color adjustments"

    JC> From: (Jacques Carrier)

    JC> Gretings from Montreal to all fellow techs,

    JC> I fixed the vertical problem on this nice 25" 1994 color TV (bad
    JC> solders). I would like to know how to properly adjust the 3
    JC> potentiometers located on the CRT board.I did not find any grey scale
    JC> pots ?? Maybe the CRT is getting old ......The colors are not crisp
    JC> enough and there is a light green hue.
    JC> If you have a service manual please get in touch with me.

    Emission might be low on the red and blue. Maybe a crt restoration would
    help. Adjusting the bias in a weak gun only leads to overload and
    flaring. Turning down the strong gun isn't much better either. If it is
    for yourself you might jump the heater series resistor. This will raise
    the cathodes' temperature and perhaps it might get enough emission back
    to clear up the green cast. Apparently the crt's in that year range were
    not very durable and went weak prematurely.

    A*s*i*m*o*v

    .... New computer? But I like my vacuum tubes... They keep me warm.
     
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