21-CT-55 has a new home

[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.

[sampson159]

there are 2 21axp22s here in columbus.i saw them last week.former repair man that passed and family has some very nice items to sell.one has a green tint to it.it checks like new and it will be sold on ebay.the other has a bluish tint and also checks well.there will be some nice b/w sets and a few roundies.ctc7 and 9,zenith roundie,admiral roundie and a partial dumont roundie.looks like rca clone.the axps would be a nice scores.the 7 and 9 are complete,working with decent cabinets.the 7 has doors on the front.they need a good cleaning and minimal touch up.since this is family-i cant buy any of these items.george was a good man and ran a shop for years in the southend.check ebay as his children are all in agreement to sell them this way.

[stromberg6]

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.

The one in my 4 also has a greenish hue to the screen, as opposed to the greyish color of most other 21AX's. Maybe an early phosphor gamut. Mine isn't really bright, but the color reproduction can be spectacular. See avatar.
Kevin

[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

[miniman82]

Originally Posted by ohohyodafarted

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.

I just went to look, and from what I can see it has the same number of pins the base does. But this particular tube was made very late in '54, so it's not like it's from the initial run or anything. In fact, the code 4-52 indicates it was made during the last week of '54.

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.

Sounds like another interesting project for a failed tube, obvisouly we would not want to destroy a rebuildable one. What is involved in the testing? Are samples taken of the actual phosphor, or just the light given off by it when excited? The observation makes sense, the screen has the same kind of look that a 15GP22 does with a little bit of sparkle I can't quite put my finger on.

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.

That's what I've always thought, but now the expert has confirmed!