21AXP22 Vs 21FJP22
 

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?

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

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.

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.

remember, We have the 21FJP22A :banana:

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?

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.

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.

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.

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

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

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

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.

There's another little story about the change to brighter red and yellower green phosphors. If a tube in an old set was replaced with one with more efficient red, the luminance drive to the red cathode had to be reduced so that the correct white color would be maintained, and RCA published a service bulletin showing how to do it.

But wait, you say, the R-Y drive goes to the grid, so doesn't it have to be reduced also?
Well, no. The new CRT with more efficient red also had the yellower green phosphor. Now, turning on yellowish green was like adding a little red at the same time, so you would want to turn off red to a greater extent than before, as the color moved from red to orange to yellow to green. This meant the R-Y gain should increase compared to the Y (luminance) drive, or in this case, R-Y drive (grid) should stay the same when red Y (cathode) drive was decreased. The increased R-Y gain compared to Y had the unfortunate side effect of making pure reds overly bright, but this was preferable to having the wrong hues in between red and green, which included flesh tones.

62 tubes! wow that's amazing! and with no tuner or audio circuits : D I think my set has only 27 tubes and I thought that was quite a lot of tubes and that's even 10 less than your 21CT55

Does anyone have a schematic for the TM-21 monitor that could be posted on the Early Television Museum web site? I would love to see what all those 62 tubes are doing!

BenMan posted one here on VK around a year ago. IIRC it got posted to the ETFs site too.

It also doubles as a heater for small homes. :D :lmao:

One can do the same with a couple of CTC15s...I sure have.
It occurs to me that one piece of program material I'm sorely lacking is yule log footage for space heater mode. :D

Yes, here it is: http://www.earlytelevision.org/pdf/rca_tm21_manual.pdf

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213 pounds! What a beast. No doubt, cabinet made of steel.

Wiscojim, thanks for the link. That's some set of circuits. Parallel tubes where only one is used in commercial TVs. Delay circuits like the DuMont Sovereign. Regulated power supplies that rival Tektronix 'scopes.

I can only imagine the quality of the picture on this monitor. Are there any screen shots in this forum?

Kvflyer, I have a Sony 36" TV that weighs 182 pounds. And there is very little metal in this TV.

I once saw the two 56" Sony monitors in the Coca-Cola headquarters in Atlanta. They said that they weighed somewhere near 1500 pounds - took a fork lift to bring them in and install them.

That looks like an RCA monitor with a 15GP22.

Tom, that is heavy. Yesterday, I picked up my RCA 630TS (10", B/W set) off of the floor... and I thought that it's 85 pounds was heavy!

Early color had to be enjoyed in subdued light
 

Even on this forum I see pix of restored color sets where the person who restored it had both the contrast and brightness cranked. In the early days doing that pretty much washed out all the colors and inaccuracy was the result.

Until rare earth phosphors were used even the early and mid-60's sets were prone to the same problem. They always taught us to set up a good black and white image and then add the color. Black levels were key. So I've seen some excellent results from both tubes, but there again it's all a matter of set up and alignment.

The 21CYP Looks notging like a 21FBP22. Glass is the only similarity.
 

The 21CYP22 looks nothing like a 21FBP. Not even close.
The phosphors are entirely different and are worlds better. It's akin to a 21axp far more than a 21FBP22.

Green phosphor is emerald green, red is like blood or a ruby, and the blue is a deep sky blue.

While the 22FBP22 on the other hand. Green is dark and "minty" and lacks a lot of range.
Red is orange in color and very poppy and "neon" making purples pop really agressiyla Nand faces a bit orange.

So no. The 21CYP22 is nothing lile the 21FBP and the phosphors look nothing alike

In my opinion the CYP22 is the gold standard from this time. It took the very best from the 21AXP and made a reliable glass tube. I have no idea why they got rid of these older early phosphors, but the color gamet is incredibly accurate and close fo real life compared to a 21FPB22. I have all three tubes here one from 1960, the other from 1965 and 1957. Virgin low hour ctc10, and Zenith 27KC20, and RCA Ctc5

I also have a CTC5 21AXP. The CYP is better than 21axp. Improved but the same basic formulation otherwise that can produce that amazing mustard yellow and accurate colors. Faces look correct and very lifelike. The color range and tone is just worlds better and the colors march my modern flatscreen Television. While the 21FBP sort of vears off into it's own.

The easiest way to tell is the vare face of the tube. The older phosphors are very ligjr grey almost white. While the later phosphors are olive in color. No this is not the glass in many cases. I do mean the bare CRT.

21FB22 is the worst for color I have seen in all roundies. I have not seen a 21FJP but I cant imagine its much better.

I need to add. I do love the 21FBP. It's still a great tube. It's definitely brighter than a 21CYP and definitely a 21AXP. But it has a very special look that makes many films look great. But for some scenes, especially anything with green or yellow/orange. Things can be a tad washed out. But anything with red in it, will practically "pop off the screen" lol

I've got all 3 as well as FJP, GUP/GVP types and some of the late size measurement/labeling rule change roundy tubes with 19V numbers.
All are capable of good pictures.
The 21AXP22 is a better tube color wise (early ones in the 21CT55 and CTC-4 had the same NTSC spec phosphors as the 15GP22. The CTC-5 is the muntz/portacolor of RCA color chassis (the low point where they cost reduced the design too much and had to back track during and after it) and can't really drive the AXP to correct HV spec...It also lacks full DC restoration. The right set to see an AXP working to its potential in is a 21CT55 or a CBS 205.

Makers were continually changing phosphor blend until settling on SMPTE in the late 60s. Different 21FBP22s from different makers (RCA, Zenith/Rauland, Sylvania, etc.) had different phosphors with different primary gamut, brightness, and phosphor power down color.
Some FBPs had green-ish phosphors, some had white phosphors, some had grey. There were also green, and black tinted safety glasses that could change the look.

The Demodulator circuit (its health), greyscale and setup all play a role in how good or bad a CRT looks.
I currently own working examples of every RCA consumer color chassis except the CTC-12, an RCA TM-21 broadcast monitor, a conrac CYB21 broadcast monitor, I've had every year of Zenith roundy (I currently keep J, M and N years), I've got rare 50s colors from a variety of makes and rare 60s roundys from a variety of makes...Easily over 25 roundys. I've seen different year RCA chassis make different pictures with the same tube swapped between chassis, I've seen a great tube swapped to a mediocre chassis make a mediocre picture.

Performance is a function of good combination, circuit performance, and setup. If you go long enough in the hobby you'll see AXP sets and FBP sets that make some CYP sets look bad. Heck my CTC-9 had me thinking the CYP was an ugly pastel looking tube, but my CTC-10 and low hours CTC-7 make it look good.

When you hit a good combination treasure it.

The Europeans chide it as Never Twice the Same Color and with the constant changes to Demodulator circuits/angles, station camera and modulator adjustment practices, and CRT phosphor over the 50s and 60s, they weren't wrong.

Thanks. This is the best summary I've seen of the wild, wild west nature of NTSC over the years. Don't forget the NTSC black level of 7.5 IRE that had no explicit reference in the signal, the extreme variability of that, chroma level and burst phase that occurred in analog cable systems, all contributing to inconsistency.