[Tom Albrecht]

I came across lots of good info online about the failure of coils in these sets. I tested all those first thing when I started and replaced five that were open. I thought this particular one in the chroma reference oscillator circuit wouldn't be particularly critical in value, since it appeared to be an RF choke intended to pass only low frequencies. That turned out to be an incorrect understanding of how that oscillator is designed, so I guess I created my own problem in the process of replacing that coil. Once it was replaced with one close to the original value, the chroma reference oscillator started working.

The circuit is basically a phase locked loop, and usually the control voltage output by the phase detector would be filtered to remove all trace of the RF. Such is not the case here -- apparently a significant RF component appears on the control line and needs to be there for the oscillator to function properly. An unusual design to me.

I'll keep an eye on the remaining white coated coils in this set, since they are obviously subject to failure sooner or later as well.

Dave, thanks for the tip on feeding a composite video signal into the video amp; that sounds like a good "divide and conquer" approach. Since I can't get a nice video signal through the IF chain just yet, that might be a morale booster to get some color on the screen earlier in the process!