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

[Sebastian Voitzsch]

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

 

[Sebastian Voitzsch]

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

 

[John]

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.