Ralph-
The problem may be bad mica coupling capacitors in the IF circuits. My 8TS30 had similar symptoms, and other collectors suggested replacing those caps. I think there are four or five of them, all the same value. Phil Nelson has a great Web site description of his 630TS restoration, including the IF capacitors.
http://antiqueradio.org/RCA630TSTelevision.htm
Here is the discussion of my 8TS30 restoration as well:
http://www.videokarma.org/showthread.php?t=251332