First off the CRT looks very strong. Hard to tell but it looks like
the purity is off. On the CRT all those little squares glued on are correction
magnets. See if any fell off. There is a chance the shadow mask in
the CRT has broken loose also.
You need a source that can give you a pure red, blue or green screen.
If the screen is say green but the corner area is not its a purity problem.
Look into that & get back to us.
BTW almost all service adjustments are through a menu. You need a remote,
possibly OEM & instructions or you can mess things up bad. I see NO reason
to mess with them anyhows.
73 Zeno
LFOD !