69 Magnavox can't keep the white point stable

[zeno]

Start by turning the color all the way down. Make it as
good a B&W set as you can & watch it for changes.
If it stays good the video is OK. Streaking is usually CRT
but can be in the video. Also if it has a horz blanking tube
try that. It will cause odd problems on old maggies &
is often missed.
Once you have a nice B&W turn up the color & work on
that if needed. Watch the plate resistors on the 6GY6's
they drift.
BTW dont trust a tube checker. Sub tubes with NOS
brand name tubes.

73 Zeno