Here's what to do:
Unplug the CRT Socket and turn on the set.
If the problem goes away, you have a bad CRT.
If the problem stays, you may have a bad filiment lead on the focus tube or a carbon trail in the socket. (Make sure that the socket that was put in is "New". Make sure it's wired right
When I worked for RCA we had a solid state replacement for the 1V2 and 2AV2. It is a simple job to install and if you like the look of the 1v2, you can leave it in place. I just put one in one of my CTC 4's. I also use a solid state replacement for the HV rectifiers as well. These perform much better than the HV tubes, create less X-Ray, less heat, and no-one cares becase they are inside the cage and you cant see them.
You can then remove the filiment wire from the tubes, eliminating a potential problem.
I have both parts. The HV solid state is a plug in, The focus rectifier is a solder in diode. You can E-Mail if you like.
Thanks,
Kirk