On 6/2/2013 8:34 AM, Phil Allison wrote:
"Smarty"
"Phil Allison"
Interesting that electron guns cathodes ( particularly the red one )
wear out long before phosphors on the tube face are history. .... Phil

I recall vaguely that the rare earth material from which red phosphors
were created was comparatively inefficient, unstable, and expensive. I
think it might have been ytrium but I may have the name wrong. Zenith
and others many decades ago proudly introduced newer and more advanced
red phosphors but I would not be surprised that they wore out faster.