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Ultrascan monitor Dell P991

Discussion in 'Electronic Repair' started by powerampfreak, Feb 24, 2007.

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  1. Hi,
    This is a Sony Trinitron monitor which I like very much. Its
    performance is awesome, unfortunately it has begun giving me picture
    troubles. Maybe a year ago, I had to continously decrease screen
    brightness and contrast to compensate for the monitor's own increase
    of these parameters.
    Today I'm using brightness of zero and contrast of say about 20. This
    will give me a decent picture. If brightness and contrast are turned
    up, retrace lines are seen. Also, the screen when it should be all
    black, is more like purple.
    This gave me an idea of a too high G2 voltage. But I was amazed when
    trying to decrease G2 (on the HVT), this actually changed the focus!
    Of course, the focus pot changed the focus aswell. It seems like there
    is some short between G2 / focus circuits???
    Any advice is appreciated. I'm an electronics engineer of switching
    power supplies so you don't need to give any advice like "bring it to
    a technician", I'm well into electronics.

    Regards
    PAF
     
  2. JANA

    JANA Guest

    Both the focus and G2 bias are from the multiplier unit. The monitor is
    designed to compensate the focus as best possible for the aging of the CRT.
    As the CRT ages, its current characteristics change.

    There is compensation for the individual electron gun emissions, and also
    for the focus voltage to maintain the best possible performance through the
    life of the CRT. There will come a time, when this can no longer be
    compensated for, because the CRT emission will decrease past practical
    limits. At the same time, there is the deteriation of many of the capacitors
    in the unit.

    From your description, you are dealing with a monitor that has aged
    components and a CRT that is starting to go weak.

    Check out the new LCD screens. They are incredible, and better for your
    health. They have almost zero EMR, no UV radiation, and no X-Ray radiation.
    Also, there are no miss-convergence or purity errors.

    --

    JANA
    _____


    Hi,
    This is a Sony Trinitron monitor which I like very much. Its
    performance is awesome, unfortunately it has begun giving me picture
    troubles. Maybe a year ago, I had to continously decrease screen
    brightness and contrast to compensate for the monitor's own increase
    of these parameters.
    Today I'm using brightness of zero and contrast of say about 20. This
    will give me a decent picture. If brightness and contrast are turned
    up, retrace lines are seen. Also, the screen when it should be all
    black, is more like purple.
    This gave me an idea of a too high G2 voltage. But I was amazed when
    trying to decrease G2 (on the HVT), this actually changed the focus!
    Of course, the focus pot changed the focus aswell. It seems like there
    is some short between G2 / focus circuits???
    Any advice is appreciated. I'm an electronics engineer of switching
    power supplies so you don't need to give any advice like "bring it to
    a technician", I'm well into electronics.

    Regards
    PAF
     
  3. Hi Jana,

    But what about G2 adjustment? Why cannot this be adjusted at all?
    I realise the automatic focus adjustment, the focus are still perfect.
    What concerns me is that I'm unable to change G2.

    Regards
     
  4. Andy Cuffe

    Andy Cuffe Guest

    Go into the color menu and run the "color return" feature. This
    should completely fix the problem. Note that it won't let you do this
    until it's been on for about a half hour.

    That monitor doesn't have a G2 pot. Both of those controls are for
    focus. One adjusts the horizontal focus and the other the vertical.
    You need to alternate between them until both horizontal and vertical
    lines are as sharp as possible.
    Andy Cuffe

     
  5. Andy Cuffe

    Andy Cuffe Guest

    No monitor has ever had automatic focus.

    This monitor's G2 is controlled through software, so there's no
    physical G2 control. See my other post about how to fix it without
    even opening the case.
    Andy Cuffe

     
  6. Thanks, Andy!

    Your advice fixed my problem !! That even without taking the cover
    off like you mentioned. Great !!

    I won't like the day when this monitor pass away, since I like it very
    much. It has very good performance, like you probably know.
    By the way, do you have a service manual for it, or more advice
    regarding common faults etc ?

    Thanks again, Andy!

    Regards
    PAF
     
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