In the course of troubleshooting this problem I reconnected RCA connector connected to the RCA input of my TV to the luma wire of AD725 in hope having precise and beautiful grayscale picture, but got the following instead for white chars on black background:
Interesting that white chars on blue background are displayed excellently (in grayscale), but when black chars on gray background screen flickers heavily at the top 1/3 of the screen.
Color artifacts look too strong for me. of course luma trap does nothing (as datasheets states).
Do I miss something, and pure luma signal from the S-video set of wires gets into chroma band so strongly?
Searched through internet and did not find much info if this connection is correct, and what result I would get (no pics and discussion of related issue).