Doug,
Your Chromix control on that Sears/Warwick set is probably based on this Warwick patent:
http://www.freepatentsonline.com/3825673.pdf
Bottom of column 1 under Color Gamut Compressor describes the Chromix citcuitry. Notice how they are talking tint control up until they start to talk about the present invention - can't call it a tint control - already part of the RCA patent!
Now I expect that some of the 15GP22 expert folks here could explain all the technical aspects of the phase relationships and all - I'm lost.
Cheers,