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Monochrome monitor questions?

Discussion in 'Electronic Repair' started by SomeBody, Dec 5, 2005.

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  1. SomeBody

    SomeBody Guest

    I'm repairing a few monochrome monitors, these are 9" in size.

    The problem I'm having is the screen has vert. lines spaced about every
    1/2 in, they are about 1/2" in width. I believe it would be called
    ghosting?

    The pc board consist of some discreet components and two IC chips.
    TDA1175 (vert) and TDA1180 (Hor). Both chips have been replaced as well as
    the tube.

    Any ideas what the problem could be, an area to look at?
    I have a copy of a schematic, but don't now how to post it here for
    viewing.

    Thanks.
    Jeff
     
  2. James Sweet

    James Sweet Guest


    If it's got vertical lines that's jailbars, you need to replace the
    capacitor that filters the B+ to the video amp, on color monitors it's
    normally on the neck board, on mono monitors it can be there or on the
    main board.
     
  3. Arfa Daily

    Arfa Daily Guest

    It can also be striations due to velocity modulation of the H-scan. It's
    common to have a line linearity coil in series with the H-deflection yoke
    windings on monochrome monitors. There is usually a damping resistor across
    this coil, to stop it ringing immediately after the flyback ( retrace )
    period. This resistor commonly goes open circuit, allowing the coil to ring,
    producing the velocity modulation of the beam as a result of the decaying
    sine wave that then gets impressed on the rising sawtooth.

    Arfa
     
  4. JANA

    JANA Guest

    Use an ESR meter and do an ESR test on all the caps, especially in the scan
    and power supply circuits. It is possible that on an older monitor, you will
    find many caps that are out of specs.

    --

    JANA
    _____


    I'm repairing a few monochrome monitors, these are 9" in size.

    The problem I'm having is the screen has vert. lines spaced about every
    1/2 in, they are about 1/2" in width. I believe it would be called
    ghosting?

    The pc board consist of some discreet components and two IC chips.
    TDA1175 (vert) and TDA1180 (Hor). Both chips have been replaced as well as
    the tube.

    Any ideas what the problem could be, an area to look at?
    I have a copy of a schematic, but don't now how to post it here for
    viewing.

    Thanks.
    Jeff
     
  5. SomeBody

    SomeBody Guest

    An -UPDATE- on the jailbar problem.

    It turned out to be some newer type FBT we installed on an older
    board, since the old style FBT were not available. We pulled a few old
    style flybacks from scrap boards and installed them on the boards in
    question. The problems on this sample lot all disappeared.

    Thanks.
     
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