Today's Mystery Guest (RCA CTC-4)

[ChrisW6ATV]

Phil, your step-by-step analysis and documenting of the process are enjoyable and informative, as always. I wish I had something to add, but I can only think that it might be an IF alignment issue.

Another trick would be, inject a color baseband video signal into the stage where you are seeing the total lack of color signals/frequencies (the lower trace in your CTC-4 scope picture) and see if the rest of the set's color circuitry works OK. Then, inject the same signal but at IF, into the IF stages one by one backwards and see if you can narrow down where the problem starts. Suitable signals should be available from your B&K 1077, I think.