RCA 21CT55 B8802897 is Alive!

[Tomcomm]

RCA started its CTV cost reduction with the first chassis after the CTC2B, namely the CTC4. A few comparisons should be noted:

.................................................. ....... CTC2B.................CTC4
Tube compliment:......................................3 7......................26
Stages of picture IF amplification:.................6.................. ......3
Stages of luminance processing:...................2................... .....2
Stages of chrominance processing:...............21...................... .10

I wrote the following in one of my earliest posts on this thread on March 23, 08:

I brought the 21CT55 into the house in 1964 after I got it working and ran it along side my Dad's old CTC4 he left me. Both had 21FBP22s so it was a good comparison of narrow BW color R-Y, B-Y vs. full BW color I,Q. The extension of full color into fine detail on the CTC2B was startling! Color persisted in fireworks until extinction that I never saw before. The CTC4 fireworks turned into white long before extinction. The CTC2B carried full color way into the shadows, the CTC4 went gray to black. I kept the CTC4 in the house for the kids but brought the CTC2B back to the garage workshop for further study.

[Tomcomm]

Now that my 21CT55 picture quality with the FBX transplant its about the same as the original, its time to return to my original 1/13/08 "....Its Alive!" thread. I think it would be good to repeat the first posting of this thread since my objectives remain the same:

I've got this 21in roundie in 1965 from a newspaper want ad, for $50 I think. It didn't work but I got it running with a few tube changes. Picture looked good on the 21AXP22 metal but was was very dim. I exchanged it at the CRT re builder for the brightest rebuilt he had, a 21FBP22 glass for $45. He told me the "FB" meant Full-Bright", what did I know? When I started the conversion from metal to glass, I decided to cut-up the cabinet and mount the chassis vertical so I could get to the under side much easier. This was no big deal since it was never going into the house and would reside in my garage TV repair workshop.This B88002897 proved to be the highest serial and last discovered 21CT55 with CTC2B chassis on a list of only 15 known to still exist! Anyway, I got it working this week after 38 years of storage. I'm using external video since the tuner/video IF isn't passing chroma yet. The 21FBP22 sure is bright, no problem with room lights. The reds are closer to CT-100 then most TV I've seen. I am truly grateful for the interest that John Folson, Pete Deksnis and Ed Reitian took in this reactivation project. I only wish I didn't destroy the cabinet, but that's life. I'm not a restoration person. I hope the restoration members of this forum are tolerant of my efforts to reactivate and possibly improve the performance of this classic color TV. I hope this explains where I'm coming from, thanks.....

So lets see if we can pickup this upbeat "....Its Alive" thread from where we left off the depressing "...Its Dead" thread.

Does anyone have a listing of all the surviving 21CT55s arranged in ascending serial numbers, including present owners? The ETM doesn't seem to have this info........Tom

[miniman82]

Originally Posted by Tomcomm

The 21FBP22 sure is bright, no problem with room lights. The reds are closer to CT-100 then most TV I've seen.

The FBP/FJP tubes have an orange-red color to me, while the earlier ones were closer to actual red. Placed side by side showing the same color bar pattern, my CTC-7 with CYP tube gets closer to actual red than the later Philco with FBP does. Since I just got a good AXP for the CTC-4, I can confirm that the AXP gets even better (what I would call more accurate) color than the CYP but at reduced brightness.

Sometime in the future I'll be doing a full writeup of all 3 tubes, so people can see the actual differences. It's slight, but perceptible.

[Tomcomm]

That quote was from Jan 08. At the time I had only observed a live 21AXP22 from 1965 when I replaced it with the present 21FB22A. the AX was so dim that I was overwhelmed with the FB brightness I didn't ponder the red purity of either. In 2008, the red purity of the FB was clearly better that all my "modern" TVs but that was due to their orangeish red Sempti phosphors in general use. I have not directly viewed a CT100 but pics posted by Pete D had reds almost identical with my 21FBP22A. Point of interest, my FB has a llight gray denergized screen while my spare FB is green. I'm assuming the gray FB in use is a "rare-earth" which has supposedly better reds than the sulfide green screen?

[Tomcomm]

Originally Posted by miniman82

The FBP/FJP tubes have an orange-red color to me, while the earlier ones were closer to actual red. Placed side by side showing the same color bar pattern, my CTC-7 with CYP tube gets closer to actual red than the later Philco with FBP does. Since I just got a good AXP for the CTC-4, I can confirm that the AXP gets even better (what I would call more accurate) color than the CYP but at reduced brightness.

Sometime in the future I'll be doing a full writeup of all 3 tubes, so people can see the actual differences. It's slight, but perceptible.

To be truly objective, you must include the gray screen 21FBP22A rare-earth. I wonder how many VK members have operating gray screen 21FBP22A's? Hopefully they also live near you and are willing to participate. How many flights of stairs did you say you had, three as I recall. LOL!

In the meantime I would like you to retake and post the 3 tv cluster pix you have. This time put the Sony closer and adjust the TVs for most accurate red and white color bars. Also pull-in to include only the TVs and shoot in total darkness. I have been playing with the color balance feature of my Photo Impact graphics program that reads the RBG values 0 to 255 of any spot on the JPG image. This is the hacker's approach to chromatic spectrum analysis but should give quantified data on relative phosphor differences of all your CRTs.
Thanks for your interest and cooperation.

[miniman82]

Originally Posted by Tomcomm

In the meantime retake and post the 3 tv cluster pix you have.

Hopefully I can get the 21-CT-55 up and running soon, then I will have a pic with a modern monitor, 21CYP22, 21AXP22A (grey), 21AXP22 (green), and green face 21FBP22.

[Tomcomm]

Originally Posted by Tomcomm

To be truly objective, you must include the gray screen 21FBP22A rare-earth. I have been playing with the color balance feature of my Photo Impact graphics program that reads the RBG values 0 to 255 of any spot on the JPG image. This is the hacker's approach to chromatic spectrum analysis but should give quantified data on relative phosphor differences of all your CRTs.

I have now performed the above Photo Impact “spectrum analysis” on some of my 21CT55 screenshots verses ’84 Sony pro monitor and ’97 Sony 27in tv. All pics were shot with the same Canon S40 and were not color enhanced. I used the DVE color bar for all screenshots tests and “normalized” each pic by placing the virtual sampling probe onto each white bar and setting the brightness to produce approximately the same digital 255 max red, green and blue components. I then placed the sampling probe onto the red bar and took digital readings of its red, green and blue components. Ideally, a perfectly pure red bar should produce a red component of 255 while its green and blue components should read zero. Only the color accuracy of the Canon camera sensor is evolved here since the LCD computer monitor’s color accuracy is never an issue. Since relative CRT phosphor chroma response is all we are interested in, any variance of these readings indicates contamination of the ideal red phosphor’s light output, right?

Preliminary estimates of red phosphor purity of a ’88 13in Sony pro monitor, a ’97 27in Sony "modern" tv and of course the 21CT55 with 21FBP22A “rare-earth” crt follows:

21in FBA.……………Red contaminated with 5.6% green and 8.2% blue
13in Sony……………Red contaminated with 12.6% green and 6.3% blue
27in Sony……………Red contaminated with 29.2% green and 21.3% blue

No wonder the “modern” TV crts appear orangish red!

[old_tv_nut]

Originally Posted by Tomcomm

21in FBA.……………Red contaminated with 5.6% green and 8.2% blue
13in Sony……………Red contaminated with 12.6% green and 6.3% blue
27in Sony……………Red contaminated with 64.2% green and 53.3% blue

Those numbers for the 27 inch Sony should correspond to a visually washed out red - something is not right with those numbers, unless you report that visually it appears that bad.

In regards to "the red bar color should normalize to (255,0,0) RGB," I'm afraid it just ain't so, for a whole slew of reasons: the impossibility of getting ideal filters in the camera, the different spectra of the displays that interact with the filters in the camera; the raw to jpg conversion in the camera having a matrix that is designed to give pleasing color, not accurate color; deliberate non-linear S-curve processing in the camera to mimic the pleasing contrast response of film; etc. etc. etc. etc.

The human eye is a much better instrument for these comparisons than a digital camera.

[Tomcomm]

Wayne, thanks for the reply. I reran the 27in Sony by brightening the white bar. It was way too dark before which caused the red bar to saturate and as you said, "wash-out". The new results:
21in FBA.……………Red contaminated with 5.6% green and 8.2% blue
13in Sony……………Red contaminated with 12.6% green and 6.3% blue
27in Sony……………Red contaminated with 29.2% green and 21.3% blue

Somewhat less contaminated but still way orangish red compared to the Sony pro and the 21CT55 with 21FBP22A. The stated 255,0,0 RGB was "ideal" with no hardware limitations. I believe this simple and cheap method of relative phosphor comparisons can be quite useful when comparing the original NTSC rated crts eg 15GP22 and 21AXP22 with the gray screen 21FBP22A. All I need is optimally setup color bar screenshots of the original GP/AXPs. I don't have much hope for a live eyeball shootout that includes the gray screen 21FBP22A, certainly not one I may witness.

[Findm-Keepm]

Originally Posted by Tomcomm

Only the color accuracy of the Canon camera sensor is involved here since the LCD computer monitor’s color accuracy is never an issue.

Wouldn't the kelvin temp of the LCD monitor backlights be an issue, or is that somehow compensated for/already calibrated/or not an issue?

Mind you, I'm a amateur with all of this, but my two LCD monitors have two Kelvin settings that affect the color spectra - 6500K (default) and 9300K.

Interesting thread! I've worked TV's for 30+ years and about all the discussion I've ever heard is from a old, now-dead TV tech that swore by the "old" RCA red versus the "new" RCA red. I guess he too would've been interested in this thread.

I'm learning, keep posting!

Cheers,

[Pete Deksnis]

Originally Posted by Tomcomm

Does anyone have a listing of all the surviving 21CT55s arranged in ascending serial numbers, including present owners? The ETM doesn't seem to have this info........Tom

Actually, about two weeks ago I updated the 21-CT-55 serial number list that was formerly on my now defunct site (thank you AT&T) with the intent of reactivating the link to it on the ETF site. I plan to do the same with the CT-100 list. I will report when the are available; I expect them to be ready by the start of the ETF convention.

Pete

[Tomcomm]

Only good pure red pix of Pete's CT100 I've got on right. Compare with pure red of 21CT55 with 21FBP22A on left. Of course very crude setup but they look very similar, depending on viewing monitor of course.