CT-100 color sync issue?

[old_tv_nut]

Originally Posted by miniman82

Bear with me here, I'm just gonna think out loud for a second...

Looking at the color bars, it appears red has bled (or shifted) over into magenta, and blue has bled (or shifted) into cyan. Looking at the vector described on your site, and taking into account the way the demod and matricies are wired in the CT-100 schematic, I'm lead to believe you may have an issue in the demod/matrix section of the set. Here's what I'm thinking: if the +Q signal were 'weak' in signal strength, would not there be more red (given that +I stays the same) leading to the mostly red bar where there ought to be magenta? It would also explain why the bar on the end that's supposed to be blue has shifted more towards cyan, since it takes -I and +Q to make blue (lack of +Q with unaffected -I).

Again, just thinking out loud and I'm probably wrong here. But if this were my problem, I'd start poking around with an ohm meter for drifted resistors in the I/Q demods (+Q specifically), or possibly weak demod or adder tubes.

As long as we are guessing: Looks to me *mostly* like too much color and tint control not quite right. MAYBE but only MAYBE the I gain ( I believe there is an adjustment) is high, rather than Q being weak; or MAYBE the quadrature transformer is a tad off 90 degrees. Need to tweak these things step by step, since any one can throw the color bars off.

[miniman82]

Originally Posted by old_tv_nut

MAYBE but only MAYBE the I gain ( I believe there is an adjustment) is high, rather than Q being weak.

Excellent observation! There is in fact a gain pot for I, it's 2R361 in the schematic: http://www.antiqueradio.org/art/RCAC...CAManual9C.jpg

[Phil Nelson]

Yes, this wonderful TV has more adjusters than a barrel of monkeys and they are interactive. I have gotten best results by following the manual procedures exactly, in the order given, even when I feel like Adjustment X might be unnecessary.

I haven't done any of the usual setup at this stage -- just stuck the chassis into the cabinet. Since I'm going to take it right back out to redo the color AFC & other things, I'll do the setup for real next time.

Phil