RCA 21CT55 B8802897 is Alive!

[DaveWM]

did you keep any notes on what you did to get a later FB to work? I have a 5 that I hope to start on soon, and not sure of the FB status.

[ChrisW6ATV]

That is a great mosaic, Tom. I might show that to people, and watch them freak out when I tell them it is all from a 1954-55 color TV set.

[Tomcomm]

Thanks Chris for the compliment. Full size pics of the 21CT55 screen-shots compared to a Sony Pro monitor is presented here:

http://www.flickr.com/photos/tomcomm/?saved=1

Dave, I hope your CTC5 fly is good. I have plenty of documentation of my CTC2B's fly conversion to a CTC20 fly, but it was a bitch to do! I wish you luck with your CTC5.....Tom

[DaveWM]

well I figure worst case I will just re do it with a FLY/convergence board from a CTC-15, and hope the various pick offs will not be too much, but hopefully at least one of the two flys will be ok.

[radio nut]

Wow, I had no idea that an early tv could develop such a good picture. I am a radio man and I have messed with b&w tv.
When it comes to color I am lost.... What does the I or Q stand for when you talking about wide bandwidth color tv?

[miniman82]

Originally Posted by radio nut

Wow, I had no idea that an early tv could develop such a good picture.

I have a CTC-7 that will make as good a picture, it's all about how you set it up. Frequently I find that old sets have alignments that are out of spec which will cause the color circuits to fall short on performance, and local oscillators that are out of alignment so you can't get correct colors. You have to follow the factory instructions for a set to operate the way it's supposed to, but not everyone has the tools to make those adjustments.

What does the I or Q stand for when you talking about wide bandwidth color tv?

See Phil's site, it's explained pretty in depth.

http://www.antiqueradio.org/RCACT-10..._Your_Color_IQ

[radio nut]

Wow ,I had to ask. Ok..... what about dc restoration? What is that? If I am right that was used for better contrast on the black and whites sets.Also does digital tv still process color the same way?

[miniman82]

Originally Posted by radio nut

Also does digital tv still process color the same way?

Not even close...

[lnx64]

Digital TV processes color as Y/Cr/Cb. (Some people think it's RGB but it's not.) Quite a difference from what NTSC uses.

[Penthode]

Originally Posted by lnx64

Digital TV processes color as Y/Cr/Cb. (Some people think it's RGB but it's not.) Quite a difference from what NTSC uses.

Actually DTV is based on the work of the NTSC. Y, Cb, Cr is essentially a digitized version of Y, Pb, Pr. These signals are the luma, and the B-Y and R-Y signals respectively, which would either be fed to digital MPEG2 encoder (for say broadcast or authoring a DVD) or would be fed to an NTSC color encoder to create an analog composite video.

[Tomcomm]

Originally Posted by miniman82

I have a CTC-7 that will make as good a picture, it's all about how you set it up......

This is a subjective opinion I find questionable.

The screen-shot comparisons of my 1954 RCA 21CT55 with its full NTSC spect'd CTC2B chassis and 21FBP22A rare-earth crt produced picture quality almost comparable with my solid-state, comb-filter 1984 Pro Sony. I checked all the RCA schematics from the CTC4 up to the CTC20 tube types. All of them have narrow equi-bandwidth chroma processing and hi level crt luminance/chroma combining. The dramatic difference in picture quality between RCA’s CTC2B wide band IQ and the CTC4 NB R-Y/B-Y was obvious to me even in 1964 as related in my first AK/VK message of March 28, 2008:

”…….When I bought my 21CT55 for $50 in '64, I brought it into the house after I got it working and ran it along side my Dad's old CTC4 he left me. Both were operating Over the Air and 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 "Show of Shows" fireworks until extinction which I never saw before. The CTC4 fireworks turned into white long before extinction. The CTC2B carried full color burn all the way into black, while the CTC4 went color to gray to black! I get really awesome displays on the 21FBP22A with vibrant, accurate color shading. Having the CTC2B's super wide dynamic range due to full bandwidth I Q demodulators feeding low level I-Q-Y matrixing , resulting in pure R G B that were amplified and applied to the CRT grids only. I kept the CTC4 in the house for the kids but brought the CTC2B back to the garage workshop for further study.”

The CTC4 was RCA’s first attempt at drastic cost reduction with the introduction of NB equiband high level R-Y B-Y demodulation and developed G-Y applied directly to the CRT grids, with high level luma +Y applied to the CRT common cathodes. This basic CTC4 configuration persisted with slight variations thru CTC5, CTC7, CTC9, CTC10 and beyond, producing quite acceptable quality pictures. However, only a side by side comparison in real time like I configured in 1964, would demonstrate the obvious superior fine-detail performance of the wide-band CTC2B. This is possible for the few VK members who have both an operating CTC2B and also later RCA roundys but impossible for me with only a single 21CT55 and a comb-filtered Sony Pro Monitor. I must therefore rely on the "stitched JPG" screen-shots I posted in this thread.

Hopefully other VK members will attempt to duplicate the "stitched jpg" screen-shots presented in this thread using a wide-band CT100 or 21CT55 and later narrow-band RCA roundys. I could provide the original 1024X768 jpg pics I used if requested........Tom

[miniman82]

Originally Posted by Tomcomm

This is a subjective opinion I find questionable

This entire thread is subjective and opinionated, what's your point? (all internet threads are, IMO)

The set itself may in fact be able to produce color farther into the background but the simple fact is that the human eye, at normal viewing distance, cannot perceive them. That's why RCA and others did away with wideband after the CTC-5 series, the extra expense was not justified. It's a physiological question, not electrical. Does that mean it's necessarily 'better'? That's the subjective question. You say yes, I say there isn't a whole lot of difference when viewed at a normal distance from the screen.

only a side by side comparison in real time like I configured in 1964, would demonstrate the obvious superior fine-detail performance of the wide-band CTC2B. This is possible for the few VK members who have both an operating CTC2B and also later RCA roundies

Since I have a finely tuned example of each chassis model from CT-100 to CTC-7, I think my input may carry some weight on the subject. (Pete, feel free to correct me should I be wrong)

Here's what it boils down to:

The human eye has greater sensitivity to variations in brightness than color, which is why you don't notice much difference at normal distance from NB to WB. If you're the type that sits 12" from the screen analyzing every detail, then the WB sets may in fact provide better visual 'fidelity'. But I would submit to you that no one watches television like that, it would be nearly impossible to actually enjoy.

Further, it's a fact that a B&W set from the same period produces a 'finer' monochrome picture than any color set ever will, because their luma channels are not bandwidth limited as the color sets were. Also their CRT's did not have a resolution sucking shadow mask.

It's the same exact argument the audiophools always use, but when presented with 2 wildly different setups for a blind test they nearly always fail to tell the difference between the system that was more expensive or 'better'.

It would be interesting to make just such a comparison live; put a card in front of a NB and WB set with the same thing on screen, and ask the viewer to pick the best looking one. These types of things are impossible via internet...

[ChrisW6ATV]

I remember watching rock concert performances on NTSC displays, and noticing massive limitations in resolution of scenes that were mostly black and blue (such as a shot of the drummer when only the blue overhead lights were on), and perhaps other black-plus-color scenes as well. Would this type of programming look better on a wideband-color NTSC display?

Incidentally, I am one of the people who would sit close and analyze every detail. I think a good viewing distance from a 19-inch display is probably about 30 inches maximum.

[Electronic M]

Leaving the realm of subjectivity for a moment....Video resolution(visual detail) in analog TV is directly related to bandwidth, so logic states that a measurable difference in the bandwidth between two color demodulators(or any other video system) will yield a measurable difference in resolution if all else is the same.

Whether or not this difference can be(or will be) perceived by the viewer is subjective, but the previous paragraph is scientific fact and not subjective.

I'd likely notice the difference as I tend to watch my sets at a closer viewing distance than most and watch for bad details to the point of annoying even myself. LOL.

[miniman82]

Originally Posted by Electronic M

....Video resolution(visual detail) in analog TV is directly related to bandwidth...

To a point: remember, there are only so many phosphor dots.