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convergence problem Zenith ZB4683RK

Discussion in 'Electronic Repair' started by Jerry, Jan 7, 2006.

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  1. Jerry

    Jerry Guest

    Hello, If you look at the pics at
    you will see what I see on this TV. The customer convergence controls
    on the front of the set act as follows:
    Red left-right doesn't move the cross hatch pattern.
    Red up-down doesn't move the cross hatch pattern.
    Blue left right does move the pattern
    Blue up-down has no affect on the pattern.
    The cross hatch pattern was generated by an old HealthKit color bar

    I replaced op-amp IC4003 and two 100 ohm resistors in its power supply legs.
    The resistors had dropped to around 50 ohms.
    Checked all of the pnp/npn output transistor pairs. They look good.

    Went around looking at the bases, collector & emitters of transistors on the
    board. Did
    not see anything that called out for closer inspection.

    I have a scope and have looked at some of the points on the convergence
    board. Not knowing
    exactly what I'm looking for I have some questions. Shouldn't the general
    shape of the
    horizontal signal applied to each of the red, green and blue coils be
    similar? If you inspect
    waveform5.bmp through waveform10.bmp at the above web site you'll see some
    of the waveforms that are applied to
    the trailer yokes. I looked at the vertical and horizontal signals coming in
    to the convergence board,
    they look good.

    I have measured the power supplies,
    the + 16 and - 16, and +,-12 and +,-7 are all close. I can post on my web
    site captured waveforms at
    points in the set. Oh yes the schematics I have are more general artistic
    renderings instead of
    actual circuit diagrams.

    Any ideas of what components I should look at? I hesitate to purchase a
    replacement module for fear I would
    be throwing good money after bad. I fixed a power supply module earlier only
    to have this convergence problem
    pop up after a few months.

  2. Jerry

    Jerry Guest

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