blue glow in HV recitifier

[DaveWM]

I noticed this when looking at my CTC-7 as HV comes up the HV rectifier will glow blue like its gassy, then as soon as you hear the crackle around the CRT and the raster comes out the blue goes away. So its only glowing for a few seconds. It's pita to get at it and replace with the flyback cage installed, so I was going to pull the chassis and remove the shield to give me better access to see what is going on. The set is working fine, but the fly does get hot after about 30 min even with the fly current only at 180ma.