[old_tv_nut]

I don't think any TV was designed so that failure of the sync IC would stop the horizontal sweep from running (a sure way to burn up horizontal outputs and/or flybacks). The first IBM PC color monitor did that, resulting in a lot of failures when they were turned on without connecting to the video/sync output of the PC. TV designers laughed at that blunder. It is conceivable that some sets had a safety feature to prevent burning a line into the CRT if vertical failed, but I can't point to one myself.