Ct-100 color osc problem

[dtvmcdonald]

My CT-100 has always had a small problem with the color sync.

That is, when there is a really bright orange, red, or magenta area just at the start of a line, that color discombobulates the color sync and I get the wrong color. Other colors don't cause the problem, because they are closer to green.

In other words, clearly what's happening is that the pulse that gates the color burst is not cutting off sharply enough at the end. Yet the scope patterns look as OK as one can tell from the small pictures available. At least that's the obvious guess.

Has anyone elee ever noticed this problem? If so, was there a fix?

[Electronic M]

Have you tried adjusting the horizontal locking phase? Those RCA horizontal osc systems allow you to synch early or late enough to roll the sync bar into the viewable area. The color circuits are gated off flyback pulses IIRC so you may be able to fix the gate timing with a simple adjustment of the horizontal.

I'd try that before going off into the weeds of adjusting a color circuit that is producing the correct waveforms.

[dtvmcdonald]

Tom: well, the horizontal hold does do that a bit, and it does affect the problem.

But I don't see any adjustment for the retrace pulse timing. The entire
horizontal oscillator circuit in my set had every non-adjustable part replaced
with modern ones due to an otherwise incurable intermittent. All values
are within 5%. The system aligns as described in the manual.

Also .. I seriously envy anybody like you with a good 15GP22, despite
the (otherwise) superb picture my "CT-100 tuner" produces on my Sony monitor!

[old_tv_nut]

I presume you're running it with the yoke and anything else involved in the horizontal sweep connected? Burst gate timing depends on the width of the flyback pulse plus whatever fixed RC shaping circuit is used to make the burst gate pulse.

[dtvmcdonald]

Originally Posted by old_tv_nut

I presume you're running it with the yoke and anything else involved in the horizontal sweep connected? Burst gate timing depends on the width of the flyback pulse plus whatever fixed RC shaping circuit is used to make the burst gate pulse.

Oh yes, its normal operation. The only oddity is that the CRT is completely disconnected. This fault has been the same since after recap I first
got a color picture.

[old_tv_nut]

Have you checked the R and C values that go from the flyback to the burst gate amp?

SAMS R193 (22k), C 155, R194, C16, C154

I should also mention that I have a similar problem with my CTC-5, and it's sensitive to the horizontal phase.

Which gives me another thought - have you tried fiddling with the horizontal locking range adjustment?

[dtvmcdonald]

I actually checked all the resistors, and the .01 uF and higher caps
are all new close tolerance parts. I did not check the two low value caps.

The horizontal locking range adjustment was tried at various settings close
to the instructed one. I worried about A38 as well, but its not the problem.

It does work properly with the horizontal hold set well away from the "sweet spot"
but this causes the system to loose sync on changing channels and to get it back I have to twiddle the control.

Seeing the problem is rare on most program material except cartoons or the
chyron on some news channels. It has to be an almost saturated bright red or
very saturated orange or magenta. Violet to green to yellow is no problem.