Thanks, I am open to all suggestions at this point.
After I saw the signal coming out of the video IF section, I disconnected that output and injected a video signal from my pattern generator. I'm injecting it at the grid (pin 2-9) of the 1st video amplifier, V110. The idea is to get the chroma circuits working first, and worry about the video IF later.
I don't have a spectrum analyzer, unfortunately.
At this point I'm thinking you're correct, that the oscillator and color lock are working reasonably well. As I understand the lock system, the local oscillator puts out its 3.58-MHz signal and the phase detector compares that frequency to the incoming 3.58-MHz signal. If they are different, the reactance tube pulls the oscillator up or down to match the received frequency.
Here's a little test that I tried after getting my frequency counter. The counter showed different frequencies (at the oscillator) when I used different sources for the injected video input. I tried this with two pattern generators and a DVD player. I assumed this was because the 3.58-MHz component from each of those sources was a little different, and the CTC-4 was able to lock on those slightly different frequencies.
Then I connected those different sources to my CTC-11 and compared what I had measured at the CTC-4. For instance, here's my Leader pattern generator feeding a signal to the CTC-4, which appears to lock onto 3.579673:
And here's the same generator feeding a signal to the CTC-11, which locks onto 3.579679:
That is the same frequency out to five decimal places. The results were similar when I compared other sources with both TVs.
This suggests that my CTC-4's oscillator is running and that it can lock on the same incoming frequencies as my CTC-11 (which has great color).
Which leads me to think that its problems lie elsewhere -- maybe in the demodulator circuits downstream, or, as you say, somewhere upstream, where the incoming signal is getting attenuated or mutilated. The chroma circuits seem to work best with the strongest injected signal that I can provide. The schematic says that the CTC-4 expects +2.7V at the grid of the 1st video amp, and none of my equipment can provide such a strong video signal. When people want to inject video on a CT-100 or CTC-2B, it's necessary to provide a little video preamp.
Anyway, I'm open to fresh ideas. Yesterday I reinstalled the original quadrature transformer, which works just as it did before.
Regards,
Phil Nelson