Resolder the ceramic resistor packs on the 9-88 & 9-89 modules.
It was a must do on all repairs. Whenever you see them resolder them.
G-2 controls were known to get bad spots on these. Funny thing is 2 of
them went for $2.50 & the 3rd were for $1.40, go figure. Needls to say
we only bought the cheap ones.
63-10137,8 & 9 IIRC. You can use them from an old hybrid chassis also.
If you change one cut the 3 leads at the pot, easier than unsoldering.
Be sure to use plastic mounts as there is boost on them.
Never had shading BUT on all other brands its common. Almost always
the 'lytic on the 200V supply to the 3 video outs. I think its in the main can ?
Second choice is a horz blanking problem.
73 Zeno
LFOD !
BTW I thinks this is a 25GC45. Let me know the chassis & I can look things up for you