Electronics Repair (sci.electronics.repair) Discussion of repairing electronic equipment. Topics include requests for assistance, where to obtain servicing information and parts, techniques for diagnosis and repair, and annecdotes about success, failures and problems.

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Sebastian Voitzsch
 
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Default TV - left portion of screen dark, not in video text mode

Hi all,

I?ve got a TV set where the left 1/4 of the screen is faded; especially
noticeable when dark pictures are showing or in the black borders of 16:9
movies.

The repairfaq points to a filter cap in the video driver stage - this cap is
OK.

With further tests I found there?s no faded left border in videotext mode
and even the border is present but much smaller with the video input via
Scart. The video signal is switched by a TDA3505 (RGB signal comes in
through SCART, goes to videotext decoder and then to the TDA3505, which
switches between signal from pal decoder (R-y/B-y - format) and from the
vt-decoder board.

Set is an ITT Stereo Color 3868, Chassis Compact D.

Any hints?

TIA,
Sebastian
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Sebastian Voitzsch
 
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Sebastian Voitzsch wrote:

Hi all,

I?ve got a TV set where the left 1/4 of the screen is faded; especially
noticeable when dark pictures are showing or in the black borders of 16:9
movies.

snip
Set is an ITT Stereo Color 3868, Chassis Compact D.

Solved. Replaced the filter cap in the 12V supply (C522, 100uF / 25V).

Cheers,
Sebastian
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John
 
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Hi Sebastian.
You just beat me to it I had this fault many years ago it's an interesting
feature of this chassis that the power supply is synchronised to the line
stage so any supply decoupling problems give a stable brightness change
across the screen.
Best wishes John.


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