gassy 21fbp22 ?

[timmy]

hey guys is there any fool proof way to tell if a crt like a 21fbp22 is gassy. i have my 63 silvertone roundie and at the anode button there is blue marks stretching away from the button towards the dag and the blue marks are clearly in the glass, is this any indication of a problem with this 21fb. this set still has hv issues that im still trying to narrow down when maybe the crt is infact gassy to be giving me false indications of a flyback or anything else in the hv section when it may be the crt all all along.