21-CT-55 has a new home

[ohohyodafarted]

Originally Posted by miniman82

It's hard to explain. You know how a 21AXP22 normally has a whitish grey look to it, like the CYP tubes do? This one has a slight, I don't know, almost greenish hue to it. You have to have another AXP right next to it to see the difference.

Nick,

The only 21AX's that have this greenish color phosphor have been mostly found in CT55's. I also have a very early CTC4 which has a 21AX with a greenish looking face. Another intresting discovery is that, at least on the crt from my 55, which was rebuilt by Hawkeye, RCA was using up the 20 pin stems left over from the production of 15GP22's, rather than using a 14pin stem as would normally be expected. Take a close look at the stem on your tube. See if you can count the number of wires by looking into the end of the neck through the neck glass. The old gun removed from my 21AX was mounted on a 20 pin 15G stem.

All this leads us to believe that the initial production run of 21AX tubes, which were used in the CT55 sets, and which have this greenish color phosphor, may be using the full gamut phosphors like were used in the 15GP22 tubes. Some day we will need to test one of these green faced 21AX tubes with a colorimiter to see if they are indeed full gamut or not.

CT55's are known for having a brilliant color picture. Perhaps full gamut phosphors are part of the reason for this. AFter all a CT55 is actually a CT100 with a 21" crt and a modified HV section. Perhaps the phosphors are also an extension of the CT100 series.

Time and further investigation will reveal the answer.

Bob