CTC-16 Green Picture

[Jon1967us]

CTC 16 Green Screen



Symptom:

Picture only displays in green.

Sams:

https://earlytelevision.org/pdf/rca_...ams-0736-4.pdf

Injecting NTSC bars:

Grayscale: https://ibb.co/QMRLcYz
Color:https://ibb.co/BcWKhyn

One sees indication that chroma waveform is present in the second picture. Color waveform osc. seems to be working, crystal checks (was substituted with no effect) ok as well, yet no color.

When set is just warming up there will be blue lines in picture that will briefly appear. Occasionally, I will see a full 3 color barber pole pattern, but only momentarily. I used to be able to tap on the color sync/color killer detector and color would return. It no longer does. I reflowed all ground lugs on the Chroma board. I reflowed tube socket connections for V17 and V19. Visual inspection having been performed several times and no cold solder joints seen. All resistors on Chroma board are within tolerance. Have checked quite a few coupling caps and they always appear to be within spec. No adjustable coils on board have opens. Pretty much every component I’ve removed from the board as a possible suspect has tested fine and leakages on caps were fine. Sprayed all pots with contact cleaner thoroughly. All tubes between IF and Chroma test fine.

Screen voltages at CRT:

Green a little high (measured 192 - should be 180)
Red low (measured 108 - should be 170)
Blue low (measured 100 - should be 175)

Waveforms and voltages:

Burst Amp V18 Waveform pin 1 ok.

Color Killer V17 waveform pin 1 appear ok.

Chroma waveform osc. V20 appears to be in working order, and voltages appear normal.

Chroma Sync Phase Det V19 waveforms at pin 1, 3 appear ok, but voltages at pins 1, 3, Color Killer Det 7, 9 are too low.

Chroma bandpass amp, V17 pin 2 - appears the sync pulses aren’t getting removed and chroma signal is weak ~2-3v p-p.
https://ibb.co/2k5wsvP

Haven’t checked waveforms downstream yet, at the demods or color amps. Seems like the problem is centered around the Chroma bandpass and Killer Detector.

Injected composite video at video amp and symptom doesn't change.

Was wondering if this symptom/cause is familiar to anyone.