Philco 50-t1483 Focus problem

[Microtrol]

Tom,
the focus coil reads a couple ohms off but well within tolerances. The adjustment when its turned up will cause the screen to enlarge a bit but the focus does not get any better. After reading around here a bit I tried lowering the brightness to a minimum and set the contrast in a dark room and the picture is better but not great. Again the focus pot does shift it but it doesn't get any better. I saw from a few posts that if the CRT is gassey, this problem will occur but i guess my next question is that none of my crt testers show bad emission or shorts (beltron 8080 and a BK465), would they be able to detect the gassey condition?
When the brightness is turned up, the screen washes out and looks even worse, I have another 12lp4 and gonna try swapping it to see if this corrects some of this and if not will look into the focus system.

Thanks