Sony GDM-FW900 Convergence Problem

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

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Bob Kos
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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.

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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

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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

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Andy Cuffe

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.


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