Problem: I have been given an old colour TV. The reception is good, but very
often, when the contrast and brightness of the TV image is low (e.g. when
a night scene is shown), the red colour slowly disappears, leaving behind
the green and blue image and many red lines.
|NotTaR of Television Sets : Disappearing Red (or other color)
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The remaining red retrace are the giveaway that this is most likely not
a CRT problem.
(If there were no red lines, it could be the filament for the red gun
of the CRT going on and off due to a bad connection inside the CRT - bad
How is a black and white picture? (Turn down the color control).
If B/W picture is good, then the problem is somewhere back in the chroma
Check the video input to the CRT video driver board and signals on that board.
If B/W picture is also bad, then you can compare red and green signals
to determine where they are becoming different. The red lines in your
description sounds like the red video output circuit is drifting and messing
up the background level, blanking, screen, or other setting. Could be a
capacitor or other component.