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Sony Monitor SCC-L22D-A (Dell) G2 Voltage ?

Discussion in 'Electronic Repair' started by Bill S., Oct 24, 2007.

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  1. Bill S.

    Bill S. Guest

    Can anyone tell me what the G2 voltage is supposed to be on a
    Sony SCC-L22D-A monitor? This one has gotten extremely bright
    with retrace lines. I don't have schematics, but I can see
    that the G2 is a regulated voltage, unlike most units.

    I determined by clipping resistors into the feedback string
    that the regulator is functioning, and an 8.2M across the
    top 10M makes it work so good that I am almost tempted to
    just leave it that way. But something has obviously changed.
    Bias and gain settings in the color menu look reasonable.
    Is there maybe a Zener reference that has gone South?

    Anyway, if I knew what the G2 voltage is supposed to be, it
    would be helpful in determining whether this circuit is the
    problem or I need to chase other things down.

    TIA
     
  2. JANA

    JANA Guest

    There is normaly a pot to adjust the G2 voltage. Look on the back of the HV
    multiplier. The pot is usually marked Screen, or G2, or Bias. '

    In a dimly lit room, turn down the G2 bias to just slightly past the point
    where the retrace lines have disappeared. This should be the correct range
    for most CRT's.

    If you find the main brightness control lacks proper range after adjusting
    the G2 bias, then look for the CRT beam biases or the master bias to correct
    for this. This is for the electron-gun grid cathode bias, not the G2 bias.

    --

    JANA
    _____


    Can anyone tell me what the G2 voltage is supposed to be on a
    Sony SCC-L22D-A monitor? This one has gotten extremely bright
    with retrace lines. I don't have schematics, but I can see
    that the G2 is a regulated voltage, unlike most units.

    I determined by clipping resistors into the feedback string
    that the regulator is functioning, and an 8.2M across the
    top 10M makes it work so good that I am almost tempted to
    just leave it that way. But something has obviously changed.
    Bias and gain settings in the color menu look reasonable.
    Is there maybe a Zener reference that has gone South?

    Anyway, if I knew what the G2 voltage is supposed to be, it
    would be helpful in determining whether this circuit is the
    problem or I need to chase other things down.

    TIA
     
  3. Bill S.

    Bill S. Guest

    This is not your run-of-the-mill TV set. It's a high end dual focus
    trinitron. The two pots on the IFT are both focus voltages. G2 is
    controlled by a shunt regulator. If there is any G2 adjustment, it
    must be from a service menu which I currently don't know how to get
    into.
    I have effectively done this by altering the regulator feedback as
    I described, but I worry about how stable this might be since
    something has apparently drifted since it left the factory, and it
    doesn't really address the issue of why this now needs to be done.
    And the change I had to make was on the order of 25%, which is
    large enough in itself to be cause for wonder...
     
  4. Adrian C

    Adrian C Guest

    The service manual is at
    <http://www.eserviceinfo.com/download.php?fileid=18433>
    3 part tar archive.

    It covers

    CPD-E500 (US/Canada) Chassis No, SCC-L22P-A
    &
    CPD-E500E (AEP) Chassis No, SCC-L22N-A

    (At a guess SCC-L22D-A could mean OEM'd to Dell)
     
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