RCA 630TS Slight Picture Imperfection

[M3-SRT8]

Hi Boys,

In the continuing saga of the 630TS, I'm trying to localize a small picture quality quirk.

The GE 10BP4A CRT is installed and adjusted. Pic looks fine, except there is an occasional horizontal band of noise, about 1" tall, somewhat faint. It travels upwards to the top, and reappears at the bottom. Not bad, but, I can't adjust it out, and I'd like to eliminate it.

Any Ideas, Brain Trust?

Thanks;

LJB 8)