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Sony GDM-FW900 Convergence Problem

Discussion in 'Electronic Repair' started by Bob Kos, Sep 30, 2007.

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  1. Bob Kos

    Bob Kos Guest

    Hi All:

    I have a Sony GDM-FW900 24" Trinitron computer monitor. This monitor was
    donated to me a couple years ago in poor condition. It underwent cleanup
    and cap replacement that put it in good working order. It has been fine
    till this morning. I powered it on and discovered areas that appeared to be
    out of focus. On closer examination, it appears to be convergence issues.
    I can sharpen the out of focus areas with the convergence controls. Of
    course, other parts of the screen fall out of convergence. It's difficult
    to tell for sure, but the problem area seems to be towards the center of the
    screen - perhaps a stripe or trapezoidal area. Also noticed is a color
    abnormality. The white background color on most screens ( Outlook, Excel,
    etc ) has a random blotchy appearance with the colors being very pale blue
    and off white. None of these symptoms have been observed by me till this
    power on today.

    I have tried using the 'Image Restore' function without success. I also
    worked the 'Landing' controls without success. I used the degauss function
    also without success.

    Any ideas on what the problem could be with this monitor? I really would
    like to get it running right again. I fear that the blotchiness is telling
    me the screen itself is failing in which case it's probably time to move on.
    I would welcome any experienced advice on how to proceed with this monitor.

    Regards,
    Bob Kos
    bobkos_at_earthlink_dot_net
     
  2. JANA

    JANA Guest

    With age, in many of the sets using the Sony Trinitron tube, convergence
    failure is usually due to the tube going weak, and also due to the HV
    multiplier and convergence assembly going bad from age.

    The cost of servicing your monitor may not be worth the money.

    --

    JANA
    _____


    Hi All:

    I have a Sony GDM-FW900 24" Trinitron computer monitor. This monitor was
    donated to me a couple years ago in poor condition. It underwent cleanup
    and cap replacement that put it in good working order. It has been fine
    till this morning. I powered it on and discovered areas that appeared to be
    out of focus. On closer examination, it appears to be convergence issues.
    I can sharpen the out of focus areas with the convergence controls. Of
    course, other parts of the screen fall out of convergence. It's difficult
    to tell for sure, but the problem area seems to be towards the center of the
    screen - perhaps a stripe or trapezoidal area. Also noticed is a color
    abnormality. The white background color on most screens ( Outlook, Excel,
    etc ) has a random blotchy appearance with the colors being very pale blue
    and off white. None of these symptoms have been observed by me till this
    power on today.

    I have tried using the 'Image Restore' function without success. I also
    worked the 'Landing' controls without success. I used the degauss function
    also without success.

    Any ideas on what the problem could be with this monitor? I really would
    like to get it running right again. I fear that the blotchiness is telling
    me the screen itself is failing in which case it's probably time to move on.
    I would welcome any experienced advice on how to proceed with this monitor.

    Regards,
    Bob Kos
    bobkos_at_earthlink_dot_net
     
  3. Guest



    Thanks for your reply. There's a new twist to this.

    Normally, I leave the monitor powered on continuously and allow it to
    go into 'standby' mode only when the computer powers off. I power my
    PC off every night. Last night I decided to physically turn the
    power switch for the monitor off and back on while the PC was still
    running. The WHOLE screen came back totally out of convergence. It
    was terrible. I powered back off and back on again and all is well.
    It looks as it always has - beautiful. There's a tiny bit of
    convergence misalignment in the bottom right corner that I am not
    woirried about.

    Should I start looking for a monitor? Is this a symptom of impending
    failure? I have a philosophy that electronic things that heal
    themselves don't tend to stay healed.

    All advice is appreciated.

    Thanks,
    Bob
     
  4. Andy Cuffe

    Andy Cuffe Guest

    That shouldn't make any difference. The only part of the monitor
    that's still running in standby is part of the power supply (a part
    that couldn't affect the convergence).

    According to the service manual, the "S" board handles the dynamic
    convergence. A failure on there could be causing your problems.
    There are two STK391-220 ICs that could be bad. These ICs often fail
    in projection TVs.

    I've seen a lot of Sony 21" CRTs that fail and cause intermittent
    convergence, but it affects the whole picture equally. If it's only
    parts of the screen, then I doubt it could be a bad CRT.
    Andy Cuffe

     
  5. Andrew

    Andrew Guest

    That is the automatic on Power-on Deguass system kicking into action. It
    sounds like you just left it on to long, any stray magnetic field upsets
    the Sony Trinitrons.

    Andrew
     
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