Does all the glass color round tubes have the brass nipple because I thought the early ones had that nipple but the later had the glass tube melted to seal. What actually holds the brass nipple on the tube is it vacuum alone.

I've seen both the brass evacuation nipple and the glass evacuation stem on different all glass roundy CRTs...I don't think it was the year so much as whether the OEM or rebuilder favored using one stem type or the other.
All the gassy all glass ones I've seen that didn't fail due to necking were copper nipple.

The copper nipple looks like it's attached to a piece of some other metal probably steel or invar(shadow mask alloy) and the other metal is fused to the glass like a metal cone would be ....So it's sort of a misnomer calling a 21CYP/FBP/FJP/GUP/GVP22 all glass if it has the copper nipple....It won't fall off if vacuum is completely lost (ask me how I know).

[QUOTE=Electronic M;3253794]IIRC from the CTC-5 I converted, the plastic insulator shroud for the metal tube (clearly visible in the photos) doesn't fit over the glass tubes.



I have never seen a CTC-5 up close before, or a 21axp22 other than pix of ones outside the set, I was not sure what I was seeing in the above shot that he showed :o

D'oh - thanks for posting that - completely forgot about the ones with copper nipples.

I tested the CRT and it seems like it was barely used. I have to ask this guy if his folks had it on just for color programs. Most of the tubes are original too. Low hours indeed.

My BK445 reads a little higher than some other 440/445s I have seen, but that's OK too. The R-G-B are so close too and cutoff is fantastic compared to most color tubes.

The best thing about this acquisition is the fact I have two spare chassis, one of them is a CTC5N DeLuxe. The main difference over a "special" being three separate Y demodulators and second stage of sound IF. I forget the other differences but the CTC5D super/special DO use same parts otherwise.