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Discussion in 'Electronic Repair' started by User, Nov 3, 2003.

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  1. User

    User Guest

    I have seen queries to this problem but no solutions. Projection tv
    loses convergence and OSD then when you depower it a loud thud comes
    out of the speakers.. Sometimes unplugging and plugging the set
    several times will bring it back but usually all you get is an
    unconverged green and blue Parental Co display to the far right or the
    screen or an illuminated raster but no video, if left off all night it
    starts working again in the morning. All critical components have been
    replace cr4118 cr402, c4401, c4402, cr4122, c4102, c4108, Q4101,
    U4101, c4108, etc. etc. When working the picture is like a new set
    with excellent pincushion control. Does someone out there have the
    solution for this problem?
  2. David

    David Guest

    Monitor the clock and data lines in the set while it is operating until it
    acts up.
    I would bet you have a problem that is causing the clock or data lines to
    get squashed.
    I have seen the tuner do this, the d/a converter on the convergence pcb, the
    pip processor, the T-Chip, and other cause odd intermittent problems just
    like what you describe.
    You are simply going to have to hook up your multi channel digital storage
    o'scope to key voltage areas and clock and data lines until you see the
    change, then you can start trying to track it down by process of

    FYI over the last several years it has become virtually imperative to have a
    multi channel DSO as many sets are now having very intermittent type of
    problems, especially on the many clock and data line controlled ic's and
    multi-processor sets. There is simply no other cost effective, time
    effective, way to track down some of the problems we see in a modern tv set.

  3. User

    User Guest

    Thanks for the advise I agree a DSO would probably narrow down the
    possibilities. PIP board convergence board and smps were all tested on
    another set so they've been ruled out. I am now suspecting spurious
    signals from the tuner are taking out the eprom. These models ctc169
    are not suppose to have grounding problems but I am suspecting this to
    be the case I will attempt to resolder the tuner connections to the
    main board as this set displays all the classic systems erratic volume
    loss of OSD loss of video etc.
  4. TV Fixer1

    TV Fixer1 Guest

    If this set has the PIP module in the can, open it up and see whether the
    rubber "buttons" inside have begun to melt; I've seen a couple of these, and it
    can cause some weird problems, as the button material becomes corrosive,
    etching/shorting traces.
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