I never received the DEFINITIVE answer on using OHMS function on your meter, instead of the "shotgun" interpretation that is being provided by using its continuity function. ( 1 ohm beeps . . . . . . .BUT . . . . . .500 ohms also beeps ! )
BUT . . . . . lets go back to the orderly procedure you followed so far with the swapping of the RED drive signal with either its companion BLUE or GREEN one . . . . . to see if we end up with a screen bleeding with that other color instead of the RED, as it currently is.
You seem to have accomplished that at three different points that would be crossroads in that signal path.
Now only the kine being suspect . . . . . . however I hope not . . . . as that would be total finality.
Lets just hope that last 'lil 'ole lady did not overly over abuse that set (on at 7.00AM-off at Mid nite- every day), to the point where it had the kines 'friggin' wheels totally worn down to the ground up rims !
Hopefully not, since your displayed RED raster still shows distinct focus lines. Otherwise a weak kine/tube would not be in focus that sharp and show focus shifting " blooming" with high brightness level advancement.
Lets now do some back stepping and refer to your initial . . .
If I raise the brightness on the FBT, it does get brighter and it does go dimmer than what it is if I want it to.
You touched what only the knowledgeable should touch . . . . . unless you marked its initial position . . . . or else, read pots center wiper to one sides terminal resistance while the set was un powered . . . . . thus, your being able to reset it exactly to found position later on.
NOW . . . .if you left that FBT . . . . .Grid 2 pot set up higher (in the CW direction), than it is supposed to be, the DOMINANT strength kine gun will display, and override.
Sooooooo, now this actually may be your situation.
Test procedure . . . . . .
Initially you get a raster on the screen and use the sets menu driven brightness adjustment to set it up to its max brightness.
Decrease the FBT's G2 pots . . . .CCW . . . direction to just black out the present RED raster dominance to a black screen..
Go back to menu and decrease brightness to minimum. ( watching the bars on the on screen bar graph, since you have a blacked out screen)
Advance the FBT's G2 pot CW to duplicate that previous brightness level .
Hook up the set to use some test composite video/vcr/video disc player or game to evaluate final performance.
73's de Edd . . . . .