Progress
Rather than pulling the set apart, I did some more experimenting.
Finally, it occurred to me to just hook up a battery to the AGC bus (like when doing an alignment) to force it into the correct voltage range.
That got me some harsh video and sound.
I disconnected the battery and was surprised to still have sound and video. After some head scratching, I realized that if I rotated the contrast control to one extreme I could get sound and video without forcing the AGC bus.
So maybe it just comes down to a bad contrast control ? More testing later tonight....
