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Wikipedia has a pretty good writeup about CRT phosphors. The original red wasn't very efficient to begin with, then 80% or so of the electron beam current never got past the shadow mask anyway to even light the phosphors. From what I have read, the original NTSC phosphors were used in the 15GP22, 15HP22, 19VP22, and early production 21AXP22 tubes. The later reds had a bit shorter wavelength and so appeared a bit more orange. The green phosphor was changed somewhere down the line as well, but I don't know when (probably starting with the 21CYP22). The original green is actually the same as the P1 used in old oscilloscope CRTs. Later color TV tubes first used cadmium doped phosphors, then later on the rare earth (yttrium and europium I think) phosphors.
The overall impression I get having read various articles about the subject is that the 15" color sets really were the wrong product at the time. This is when 21" B&W sets were common, and you were going to pay lots of money to get what is effectively a 12" round CRT color picture. Add to that the weird and expensive construction of the 15GP22 and that's probably why these sets were sold at fire sale prices soon after being introduced. The CBS 19" CRTs seem to be even less common than the 15" ones. It took RCA with the 21AXP22 to get color TV sales off the ground, and it still took over a decade for color TV sales to reach 50% of total.
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Erich Loepke
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