FOUND! ARVIN 9219-cm-uhf television.

[Yamamaya42]

Originally Posted by bandersen

Stray electrons hitting glass likely. If it was air leaked in it would be purple.
Make doubly sure the ion trap is position correctly. If the beam hits metal it can vaporize and cause a burn on the screen.

I have no reference on this CRT for the trap, other than the standard, brightness all the way down, and position for best display.