Restoration begins on Ed Reitan's CTC-7

[benman94]

I've done tests with a colorimeter on the following tubes:

• 15GP22
• 21AXP22 (green screen)
• 21AXP22A (paper white screen)
• 21CYP22 (grey-blue screen)
• 21CYP22A (grey-blue screen)
• and finally an early 21FBP22 (puke green screen)

The blue shifts slightly toward violet and away from a more cyan color over the years, the red also shifts toward orange, but the greatest shift is in the green. The P1 "Kelly greens" are gone by the time you get to the 21AXP22A; the green phosphor is already substantially more yellow, and the trend gets worse with time.

The persistence of the phosphors seemed to vary somewhat as well, with some tubes, like the 21CYP22A having a bit more lag (something I've noticed, and apparently Pete Deksnis has as well according to his website).

The strange red phosphor I'm referring to in the 21CYP22A blows out to orange with high beam current more readily than the non-A version, at least in my experience. But, the 21CYP22A is much, much brighter than the non-A version. You pays your money and you takes your choice.

I'm unusually picky about how my color sets are set up however; I always drag out a colorimeter to set the white point, check grey-scale tracking, and I ONLY watch my sets in a blackened room. If you're eyeballing the grey-scale and watching in a room with any light, you more than likely will never notice the smaller differences between the CRTs, only the larger ones (say the difference between a 15G and a 21FB).