My $5 Find

Originally posted by Unimatic1140
. . . I just went downstairs and took a good look at that tube, there is a sticker on it that says its a HR21FBP22A "Hi-Light". So it must have been installed sometime in the mid or possibly late 60's. What exactly is a "Red Earth Rare Phosphor"?

The 21FBP22-A & 21FJP22-A were introduced in 1964. Since yours is a replacement, chances are that it was made in the mid to late sixties, or even later. The main difference in the "A" version is the use of a rare earth phosphor for the red phosphor. The original used sulphide phosphors for all three colors, but in the "A" version the red phosphor was changed to a yttrium/europium "rare earth" phosphor, providing even higher brightness and truer reds. The green and blue phosphors in the "A" version remained the original sulphide types.

The 21FBP22-A can be used as a higher performance replacement for the 21FBP22, 21CYP22, and 21AXP22. The 21FJP22-A can also be used if it has been delaminated.