21AXP22 Vs 21FJP22

[Rocket]

Ive seen the APX mentioned around a few times and I am curious to know the differences between these 2 tubes? One better than the other?

[old_tv_nut]

21AXP22 is the original 21 inch round color tube with a metal cone. 21FJP22 is a much later generation round all-glass tube, which includes incremental improvements such as improved brightness phosphors (of several types over the years, culminating in tubes with rare-earth red) and other changes such as better color purity. The metal-cone tubes were also prone to develop leaks at the seals between glass and metal or metal to metal, which were non-existent with all-glass construction.

The 21FBP22 was preceded for a brief time by the all-glass 21CYP22.

A paper on the 21CYP22 improvements is at:
http://www.earlytelevision.org/pdf/d...eview_9-55.pdf

[Electronic M]

The metal cone makes it impractical to mount an AXP into and FBP set but the reverse is possible, though mounting hardware modifications are often needed.

The tradeoff of the rare earth phosphors is decreased color gamut to get increased brightness. The 15GP22, and to an extent the 21AXP22 use the phosphors that the NTSC color system was designed for, but later tubes do not.

The CYP was basically an FBP with 2 anode connections.

[Rocket]

Most interesting indeed! Great read too. Sounds like both have their pluses and negatives. But sounds like the earlier APX may have a better picture, but at a trade off. I have noticed the red seems a little different on my FBP. I figured I just didn't have it adjusted just right.

[Yamamaya42]

Originally Posted by Rocket

Ive seen the APX mentioned around a few times and I am curious to know the differences between these 2 tubes? One better than the other?

remember, We have the 21FJP22A

We are better than the lowly 21FJP22!

rare earth phosphors.

[Rocket]

Originally Posted by Yamamaya42

remember, We have the 21FJP22A

We are better than the lowly 21FJP22!

rare earth phosphors.

Most interesting! So the A on the end has the Rare earths then huh? and I take it that is better?

[old_tv_nut]

Actually, the major change was in the green, because the sulfide green was much yellower than original NTSC willemite green (oscilloscope P1 green phosphor). The red did change slightly when sulfide red was used, due to saturation and an orange shift at high beam current. Rare earth red brought the red back close to NTSC spec.

Blue was shifted very early (perhaps in some versions of the 21AX?) when sulfide blue was introduced. The sulfide blue was more violet than the blue in the 15GP22, and was closer to the blue that the RCA engineers really wanted. The 15GP22 used a non-sulfide blue because sulfide blue could be contaminated in the 15GP22 production process and turn green, and that got written into the NTSC specs.

So, the divergence from NTSC phosphor colors started early, with partial compensation by changing the color demodulation angles/gains/matrixing lagging behind. This never got fully fixed until PAL and HDTV adopted the modern phosphor set, which also transferred over to computer still images as part of the sRGB standard used in jpg.

The main loss of color gamut in modern displays compared to NTSC is in the cyan (blue-green) region due to the yellower green primary.

[Yamamaya42]

Originally Posted by Rocket

Most interesting! So the A on the end has the Rare earths then huh? and I take it that is better?

if you look at the sams for the CTC-16 vs 16XL
you will see that the 16 has the 21FJP22 and the XL has 21FJP22A (better CRT)
and better set.

[old_tv_nut]

Originally Posted by Rocket

Most interesting! So the A on the end has the Rare earths then huh? and I take it that is better?

For the reason that the red phosphors before rare-earth red were only about half as efficient as the blue and green, so pictures were dimmer and current ratios in the three electron guns were not equal. Rare-earth red phosphors allowed the currents to be much more nearly equal, with less highlight blooming (defocusing), so a better tradeoff of sharpness vs. brightness.

The unequal current needs were also partially compensated by specifying a cyan-blue white color ("9300K + 27 mpcd") which also contributed to the mismatch of colors from what was intended per NTSC specs, and unfortunately made variations in transmission more visible.

Edit: one of the secrets of Zenith sets that made the colors look different (and most would say better) was use of a less blue white point.

[Rocket]

Most interesting that there was such a wide range per say of tubes and tech! I can see why now ive heard NTSC called never the same color lol.

So what do HDTV's and LCD displays use for a standard these days? I will be interested to see what my 16xl will look like next to my flat panel with the color bar generator.

I wouldn't mind a zenith color set also : D lol

[old_tv_nut]

Most computer monitors follow sRGB standards, more or less.
Digital TVs follow ITU REC 709.
The primary colors for these two standards are identical, but the gray scale contrast (gamma) is somewhat different.

Your results with comparing the 16xl to a HDTV will depend greatly on the white point and gray scale tracking of the XL along with the color demodulation gains and angles that RCA designed in to get a pleasing picture with non-NTSC phosphors and the general camera colorimetry of that time, which was also being tweaked empirically to give good results on studio monitors with non-NTSC phosphors. For a number of years, NTSC studio monitors included a matrix adjustment that could be switched on or off, intended to compensate for the non-NTSC phosphors in a way similar to what TV receiver makers were doing. Did camera makers tweak for matrix-on or matrix-off or a compromise? I don't know. The electrical matrixing in NTSC chroma modulators was strictly NTSC, but the signals going into the modulators necessarily were matrixed to at least compensate for the color splitting optics.

Note: the original NTSC cameras did not have matrixing due to the increased noise it would cause, but the optics were tweaked with color "trimming filters" to match NTSC specs. So, when later cameras and picture tubes came along, it was sort of a case of the train conductor setting his watch by the factory whistle while the factory manager set his clock by the train departure. The only thing that made it stable was the establishment of SMPTE monitor standards, but there was still that matrix-on or matrix-off dilemma. It was finally settled in PAL and HDTV when everyone decided that the cameras should be tweaked to match the modern phosphors instead of NTSC, with no tweaking in the monitors and TV sets.

[Rocket]

Originally Posted by old_tv_nut

Most computer monitors follow sRGB standards, more or less.
Digital TVs follow ITU REC 709.
The primary colors for these two standards are identical, but the gray scale contrast (gamma) is somewhat different.

Your results with comparing the 16xl to a HDTV will depend greatly on the white point and gray scale tracking of the XL along with the color demodulation gains and angles that RCA designed in to get a pleasing picture with non-NTSC phosphors and the general camera colorimetry of that time, which was also being tweaked empirically to give good results on studio monitors with non-NTSC phosphors. For a number of years, NTSC studio monitors included a matrix adjustment that could be switched on or off, intended to compensate for the non-NTSC phosphors in a way similar to what TV receiver makers were doing. Did camera makers tweak for matrix-on or matrix-off or a compromise? I don't know. The electrical matrixing in NTSC chroma modulators was strictly NTSC, but the signals going into the modulators necessarily were matrixed to at least compensate for the color splitting optics.

Note: the original NTSC cameras did not have matrixing due to the increased noise it would cause, but the optics were tweaked with color "trimming filters" to match NTSC specs. So, when later cameras and picture tubes came along, it was sort of a case of the train conductor setting his watch by the factory whistle while the factory manager set his clock by the train departure. The only thing that made it stable was the establishment of SMPTE monitor standards, but there was still that matrix-on or matrix-off dilemma. It was finally settled in PAL and HDTV when everyone decided that the cameras should be tweaked to match the modern phosphors instead of NTSC, with no tweaking in the monitors and TV sets.

It's incredible the amount of work and everything involved that goes into making color tv work! and that a hard standard for it didn't really happen until HDTV.

So I got to know what your favorite tube color TV set is? : D

[old_tv_nut]

Originally Posted by Rocket

It's incredible the amount of work and everything involved that goes into making color tv work! and that a hard standard for it didn't really happen until HDTV.

So I got to know what your favorite tube color TV set is? : D

Don't have a particular favorite, just like to contemplate the steady improvement over the years, and at a continually dropping real price. But it's also impressive to think about how much was accomplished in tube sets, before it was possible to throw hundreds or thousands or billions of active devices into a product using semiconductors.

Edit: I do have a favorite color TV tube circuit, and that's the RCA X-Z demodulator and matrix circuit. The matrix circuit includes a sneaky DC restoration effect with the horizontal blanking pulse, which is essential for preventing the gray scale tracking from drifting with either demodulator section drift or scene content changes, yet no RCA or other service publication ever explained it fully.

[Rocket]

Originally Posted by old_tv_nut

Don't have a particular favorite, just like to contemplate the steady improvement over the years, and at a continually dropping real price. But it's also impressive to think about how much was accomplished in tube sets, before it was possible to throw hundreds or thousands or billions of active devices into a product using semiconductors.

Edit: I do have a favorite color TV tube circuit, and that's the RCA X-Z demodulator and matrix circuit. The matrix circuit includes a sneaky DC restoration effect with the horizontal blanking pulse, which is essential for preventing the gray scale tracking from drifting with either demodulator section drift or scene content changes, yet no RCA or other service publication ever explained it fully.

Indeed, it already impressed me that we accomplished color tv as early as we did. now that I have been learning more about it, its even more impressive! Up until HDTV this set of mine has an amazing picture that's about just as good picture as a newer CRT tv's ive had.

Now that's interesting, I wonder if they even fully understood what was going on then? hehehe

[Electronic M]

It's hard to pick one favorite! There were a LOT of good performing chassis through the years that each had strong points and weak points.

My TM21 roundy broadcast monitor could probably beat all comers (If I can just get the darn horizontal stable for more than 5 min at a time), but it has unfair advantages of baseband video and being over-engineered to standards that make my 21CT55 seem like a GE portacolor (62 tubes just for monitoring color video where the 21CT55 also tunes broadcasts, has sound circuits and makes due with 37 )...

Someday I when I have my own house I gotta get all my TVs on one floor so I can side by side compare stuff that is split between bedrooms and basement.