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've got a 3in Pilot and a Norelco projector TV that I intend to get working next.
I am truely grateful for the interest that John Folson, Pete Dexnis 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. In 1957, I installed a 346ci Olds V8 engine in my 1954 Healey roadster. Then in 1964 and 2000 I reworked the car's frontend to resemble a Cobra roadster and installed a 418ci Olds V8. I now I have over 400hp in a 2500# car that is a drastic improvement over the original. These modifications made it virtually impossible to restore the Healey to its original configuration even if I wanted to, much to the disappointment of the Healey restorers. This RCA 21CT55 reactivation is history repeating itself 50 years latter. I hope the restoration members of this forum are more tolerant of my efforts to restore and possibly improve the performance of this classic color TV then the restoration members of the Healey car clubs. I hope this explains where I'm coming from, thanks.....Tom

Great job getting 'er going again. Do you plan to restore it to original?
Mark

Awesome picture, and great story! Glad you came on and shared!

I congratulate you on your great success! Back around 1975, I saw an ad in a magazine by RCA that featured a 21CT55 that had supposedly been bought new by a family, and had been under contract with RCA Service Co. since. The ad showed a screen shot of a macaw, and told of the "updating" of the TV with a new CRT (presumably a 21FB), the idea being that they can keep your RCA TV going forever, IF you have a service contract. Don't know which mag it was in, but it made an impression.
I have yet to see a 21CT55 in operation, but we do have that CT-100 in the museum in Windsor, CT. Fired it up last Sat night for our holiday party using a "Cinderella" DVD. The CTC-2 and 2B are incredible chassis!
Kevin

Wait a minute... What's with that horizontal cabinet with upright chassis ???????

I am assuming that it was some sort of custom built-in, or something? Is there any RCA model number on the cabinet (other than 21CT55), or is that a custom cabinet, or a Clubman series?

When I first glanced at your avatar photo of the set, I thought it was a CTC-4. Then I saw that it's a 2B.

Charles

Back around 1975, I saw an ad in a magazine by RCA that featured a 21CT55 that had supposedly been bought new by a family, and had been under contract with RCA Service Co. since. The ad showed a screen shot of a macaw, and told of the "updating" of the TV with a new CRT (presumably a 21FB), the idea being that they can keep your RCA TV going forever, IF you have a service contract. Don't know which mag it was in, but it made an impression.
Kevin

I recall that ad. I was in Jr. High and thought that was the neatest thing I had ever seen. I could not remember exactly what model it was but I remember the colorful macaw. If I recall properly, there was an older lady (the owner) standing next to the TV. I think it was either in Time or U. S. News or something like that. It was in a class where they had us read from magazines or periodicals for part of the class, must have been english or literature or something like that. I thought that I would like to have a set like that sometime and many years later, I do!

Gilbert

It's a 21CT55 with a CTC2B chassis for sure. I cut up the cabinet so I could mount the chassis vertical. I used the removable top as the base and cut the front panel's lower control portion off and mounted it to the front panel side. I explained all this in my thread's introduction, please read it. Attached is my original 1960's concept drawing and some recent detail pics.....Tom

Thanx for posting the detailed photos...since this set is more rare than a CT-100 I am glad to see it operational in any configuration..Great picture on the set btw

...

At least you kept it! Forty years ago, who knew how rare these would be.

Thanks for your response to my 21CT55 postings. Seems the screen display keeps getting more impressive as I learn thru trial and error how to get it setup properly. It operates as a video monitor with the imbedded IC video op-amp I installed that presently allows two matched switched inputs to the CTC2B's 1st video amp grid. This 3vpp level matches the original RCA designed diode video detector output. Those engineers did everything right on these first CTVs in 1953. I went to work for RCA in west Los Angeles in 1953 straight out of high school as a lab tech. Made engineer in 1956. I did defense stuff, no interest in color TV until my Dad won a new '56 CTC4 in a raffle. I stayed up the first night till 3am trying to "improve the convergence". Not a good start in color TV but I was hooked on the technology.

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 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 which 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. Ease of working on the chassis and CRT "forced" me to destroy the cabinet and configure the remains into the vertical chassis configuration I am blessed with today. That’s alright with me. I respect the original CTV restores but that’s not my thing.

Since ota NTSC is headed for oblivion in Feb '09, I see little incentive to go thru the futile exercise of getting the chassis's tuner, video and sound IF sections operational. I intend to open the heater string to all involved tubes and just let them hibernate. Probably lose about 100w off the present > .5kw it draws from the "mains". I've got plenty of quality NTSC composite video sources to keep the "old guy" demonstrational indefinitely. In addition to the C-Band Big Dish analog and 4DTV digital I've got a Koss DVD player (don't laugh) and a Magnavox Laser Disk player with about 20 disks including most of the Star Wars transfers. And of course, I expect to get my ASTC tuner coupons any day now (sic) for ota digital reception. I'm sure I'll be disappointed with the PQ of network SDTV, but then its free.

Big problem now is the poor quality of off-screen digital camera images. I get really awesome displays on the 21FBP22A with vibrant, accurate colors. Having the CTC2B's super wide dynamic range due to full bandwidth I Q demodulators feeding low level I-Q-Y matrixing to the CRT grids only. So I grab my Canon S40 digital and try to capture what I see. Results are disappointing to say the least. I tried everything possible with this full feature camera to no avail so far. If I manage a good shot, its got moiré that I can't get out. Surely there must be a technique described that will allow me to convey the picture quality of this 53yr old beast in digital camera form for emails and on the web? Anyone out there have good results or is my disappointing experience typical? I need to show the CTC2B's picture to some knowledge person on site in real time to get their opinion and critique.

I live in the country, 25mi north of Santa Barbara CA. This is wine and horse country, not techi antique Hi Fi, color TV and classic car country, so I don't communicate with anyone who shares my interests. If any of you ever get out my way, let me know, I'd surely like to show you what I got here. Right now is the best time, all the hills are lush green and the oak trees are fresh with new leaves .....Tom

I have long been impressed by the engineers who developed these sets; I think they would be impressed by the experiments still taking place with them. I wouldn't want everyone to do this with their 21CT55, but I'm glad you can.

I think you must be some sort of a mad genius..And that's meant as a compliment...But I think most of us in the Olde TV hobby are about a half-bubble or so off center anyway, at least...(grin)

The extension of full color into fine detail on the CTC2B was startling! Color persisted in fireworks until extinction which 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'm sure I'll be disappointed with the PQ of network SDTV, but then its free.

Big problem now is the poor quality of off-screen digital camera images. ....So I grab my Canon S40 digital and try to capture what I see. ....If I manage a good shot, its got moiré that I can't get out. .....Tom

A few comments:
Color saturation on fireworks details - yep, that's what wideband chroma will do for you - you get the same effect only better when you run a digitally mastered DVD through component inputs into a modern set.

Full color into the shadows - actually, in a dark room, any set *should* do that - but the CTC-4 and some other sets after yours apparently had very non-linear chroma amps, since the color control operated by changing the bias of the amplifier tube. We noticed this at ETF when trying to adjust the color level on "The Wizard of Oz."


Screen shots - On the moire' problem, it of course comes from the phosphor dots on the TV screen vs. some other regular structure - maybe the pixel structure of the camera, but maybe in the computer program that is scaling the image for viewing on the computer monitor. Try zooming your viewing program to 1:1 view and see if you have a clean image without moire'. If so, then try looking for some other viewing software. Sometimes the viewing software does a cleaner job of reducing resolution for file storage than for display. Try reducing the resolution and viewing the reduced file. If nothing works, you may need a different camera with more Megapixels. Note also, if you are really clearly resolving the phosphor dots, your image will either look somewhat dark, or the dots will be overexposed since they are only a part of the image area. The latter can ruin the contrast and saturation of the image. [Note: There used to be a similar problem taking film pictures of black and white sets that had clearly resolved scanning lines.] So, examine what you are getting at 1:1, and try reducing the exposure somewhat when you take your pix if necessary. Slightly dark will look better than compressed gray scale and chroma.

One other thing - the picture quality with a converter box (especially for prime time stuff broadcast in HD) should be excellent - the converter boxes usually have fairly wideband chroma, feeding the wideband digital R-Y and B-Y into a chroma modulator.

I'm using a Canon S-40 with 4Mpixel and 3X optical zoom. My photo processing program is Ulead PhotoImpact SE which I've used for years. I intend to checkout the suggestions of " old_tv_nut " but have tried just about every combination already. Maybe there's a silver bullet in there somewhere? I even tried my wife's 7Mpixel Olympus with 18X zoom, no better.

Presently I'm attempting a precision dynamic conversion on the CTC2B which feature separate vertical and horizontal coils on the three magnetic assemblies. Uses 9 pots and 3 trimcaps which should reduce the interaction of horz and vert during optimization. So far I've come close but not good enough. Its really driving me crazy going round n round, getting nowhere.

I even tried my wife's 7Mpixel Olympus with 18X zoom, no better.



Now that doesn't seem right - you should be able to get a reasonable result with one of these two cameras - hope your experimenting bears fruit.

...

...And now, we're gonna flush NTSC down the terlet. Nice. Way to go, FCC..

I've finally got the dynamic convergence acceptable, not perfect. Best advice..... "Know When to Quit" or you'll drive yourself nuts!

The CTC2B's original 21AX22 had the first magnetic convergence and was straight foreword but highly cross-coupled. No control was completely independent.The very next RCA, the CTC4 ,was simplified and designed for quick setup. All remaining RCA's continued refining the dynamic convergence and presumably improved its performance??

Once I had better convergence I noticed a major improvement in the fine detail inthe screen pictures, as expected. I then went back to making digital camera screen-captures as close to the real thing as possible. The CTC2B using the 21FBP22A was capable of greater brightness dynamic range then the Canon S-40 4mpix! Even going fully manual shutter speed and aperture settings with ISO 400, I couldn't capture the dark areas on the screen without driving the brighter areas into saturation.

The Canon's native resolution is 2272 X 1704. My CRT computer monitor max is 1280 X 1024 but I use 1024 X 768 for all my photo editing and display. This mismatch, in addition to the TV's CRT pitch makes for hideous moiré on lmost all captures. I started to mess with my Ulead PhotoImpact editor to reduce the 2272 X 1704 Canon shots to exact multiples of the monitor's 1024 X 768 resolution. At 1:1, suggested by "old tv nut", the moiré was greatly reduced but replaced with a uniform artifact that gave a grainy affect to large areas of saturated color. I then went to 2:1 or 2048 X 1536 resolution which was much closer to the Canon's native. The residual moiré was no worse then the 1:1 and the artifact remained, but was much finer and not nearly as noticeable. Since the edited picture had twice the resolution of the monitor, the displayed fine picture detail was obviously better than the 1024 X 768. Needless to say, work will remain in progress in this picture quality area.

I see line structure in all the pix except the convergence pattern. Since I don't see any shutter effects, I presume your shutter is slower than 1/30 second and captures both interlaced fields. Then the visible line structure could come from some degree of line pairing.

Something to try: turn the vertical hold very slightly and see if the line structure changes.

Regarding the moire' problems - are you defining a picture reduced to the monitor resolution as 1:1? That's not what I meant. I meant the same size as the camera original (2272x1704). Set the photoimpact zoom at 1:1 to get this. The picture will exceed the size of your monitor screen, but don't worry about it. You should get the least moire' problems with this setting. Then, if you do see moire' with smaller zoom settings, you can ignore it since you know thje capture is good and it's just a display problem. Once that is settled, you can work on reducing the size for posting. Whatever you do, view the reduced picture at 1:1 zoom setting also for minimum moire'.

One other thing to try, in case there is some problem with the scaling between the monitor native resolution and the 1024x768 input you are using, is to temporarily set your video card to 1280x1024. You may not like the small icons and text you get, but you will elminate any possible scaling problem there. In general, it's best to not do any resolution changes anywhere along the chain when trying to determine if the original capture is clean.

Your comment about dynamic range is interesting. I see you are using the video essentials DVD to feed the TV. Your computer monitor must also be set to the correct black level, or you will have dynamic range viewing problems. Check out http://www.daproducts.com/calibrate/ for example. It is also possible to use the video essentials DVD to calibrate video playback on your computer, but caution - this calibration will occur within the
dvd player program and will not adjust still image viewing with other programs.

The 21CT55 with a 21FB22A rare-earth CRT is operational and installed in my tiny lab where it will stay as long as I stay. IMHO, it has demonstrated it is capable of displaying a picture that is comparable to a Sony PVM1334 broadcast monitor at normal viewing distance of 3ft to 8ft. The comparisons of Sony vs RCA is presented here:

http://www.picturetrail.com/sfx/album/view/19914223

Like all my projects, work will always be in progress. Right now I am attempting to replace all the generic ferrite cored low SRF video peaking and filtering coils I used to replace the original RCA custom air cored, high SRF, universal wound coils that open circuited. Hopefully this re-coiling will reduce the slight ringing on video transitions and the chroma bleeding into the Y luminance video due to improper demodulator filtering. Click thumbnail to enlarge, than click lower right corner to super enlarge....Tom

Wow...

That's all I can really say.

One of the rarest TV's in the world, akin to the CT-100, except with a larger screen.

Wow...

I'm in love...

...

Thats awesome! Just think, these are photo's we are looking at. I can only imagine how much better the picture looks in person. Great job!
-Tony

Those screenshots are absolutely STUNNING!

After a few months activity on a couple of my 70s rectangle ss tvs I got back to my "custom installed" 21CT55. It had been ignored for about four months and I was curious if would come up with the same demonstrated picture quality it had before. It did after a 15min warm up and all was well.

I'm now running the AC power input off a computer power stabilizer and a big Powerstat so I can maintain the same voltage out of the silicon rectifiers that replaced the original selenium rectifiers. I adjust the Powerstat for a nominal B++ of 400v specified by RCA. This occurs with an AC input of 110vrms. Since I don't have access to an ultor HV meter probe I run the HV adjust fully cw max. At this setting I read a boost of 1010v! Nothing seems stressed, everything in the HV cage looks normal and the HOA 6BC6 has no plate glow or blue gas. I get very good focus and run the horz size at minimum. Gray-scale is near perfect, with very good PQ. RCA rates the
21FBP22 ultor at 27.5kv max. I may be exceeding this, but ignorance is bliss.

The only real problem I see with this operation is a very slight uniform screen glow in a totally black room with no video applied and the brightness, contrast and color fully ccw. No glow is seen at turn on and holds black for about 5min then ever so slowly starts becoming noticeable. This increases with time and becomes quite noticiable when compared with the Sony monitor after about 30min. I reduced the HV adj to min with no difference in glow.

I used my newly acquired Sencore CR70 (ebay $149) to check for element leakage that prevents complete gun cutoff, all read good. Cutoff on the CR70 all made the Good Box and all emissions were at half good meter reading. the lifetime test on each gun went into the bad zone when the heaters were reduced 25%. Seems like a good candidate for a mild Auto Restore. Only problem is the CT70 increases the heaters from 6.3vrms to 12.5vrms for 40 seconds during each gun test! That bright yellow heater glow scares me on such an old crt, so I'm reluctant to rejuvenate.

I would appreciate any comment on this cutoff glow phenomena and the advisability of submitting this really neat crt to unnecessary abusive. Tom

Your set works and looks gorgeous! I would just use the 'ol 8 volts method if you are unsure of a restore. It sounds like that is all you need. I would let it sit at 8 for about 2 hours and then test after it has cooled down. I too have the CR-70, I don't often use the restore, but did try to damage a dead CRT one day just to see what I shouldn't do, well, it just wouldn't hurt it. It shut down before any damage was done. This almost dead CRT is still functional. The CR-70 is probably one of the safest on your tube. But, like you said, why take a chance on such an old and rare CRT. The most I have used the auto-restore is on a weak tube that didn't come back on 8 volts. I interrupted the restore after the first 7 or so second burst that it gives. I didn't let it go all three times as per the instructions. It also says that interrupting the restore is ok if you want. Tube came back nicely. I try to be as gentle as possible.

---

I gotta agree with andy, the picture on this set is about as flawless as possible. I gave advise on the CR-70 in general, I apologize for not being more specific about this particular tube. After rereading your post Tom, I see a part I didn't pay close enough attention to. If it drops to bad on the life test, it's not the end of the world or a bad tube. At first, I thought you had a tube with a reading of 25%, not a filament drop of 25%, duh on my part. The life test is somewhat accurate but I wouldn't put too much faith in it. Any tube that tests good and equal on all three guns should be left be.

excellent job of restoration! Congratulations.

I used to have a repair shop, and did home TV service for Sears for several years in the late 1980's and early '90's.

I have NEVER seen a color picture that looked as nice as the images you supplied us here on AK. Your set is incredible!

I could say that my CTC-12 looked similar, but I'd be lying a blue streak, and lightning would strike at any time.

Keep it up!

Bruce

The RCA 21CT55 has been permanently installed in my lab, operating as a composite monitor for over a year now. It is powered-up occasionally and has retained its picture quality as posted previously:

http://s677.photobucket.com/albums/vv134/tomcomm/55%20RCA%2021CT55%20TV/?start=all

I am really impressed with the awesome cabinet and chassis restoration performed by AK member Bob Galanter. His serial # B880 1131 is among the earlier production while my #880 2897 is very near the end of production. His is the 17th known survivor, mine is the 16th. What's the latest info on the other 15? Who has them? How many are operational? How many are being restored? Which ones are owned by AK members?

Seems these rare second RCA production CTVs are seldom discussed on AK except when a member starts a restoration or ends one. I welcome any replies from all 21CT55 owners or interested others, regarding their present activity and possible progress towards getting these ultimate roundies operational. I'm aware of at least six AK members that have indicated they have 21CT55s. I would greatly appreciate their replys to this request for current status information. Thanks......Tom

Tom:

My 55 is in working order but still has some convergence issues. I have not had time recently to work on it but hope to get back to it shortly. I don't have the serial numbers here at work but can supply those to you later if you wish.

Steve

When I first got my 21CT55 operational about a year ago, I replaced the two huge selenium rectifiers with a couple of 800PIV, 20A silicon diodes. This raised the 400v B++ buss from a sub normal 390v to supper normal 420v when operating from my local 115vrms mains. Everything worked OK, but I set my Powerstat down to 110vrms which lowered the B++ to 400v. It remained at 400v for all my convergence setup, picture quality evaluations and screen shots. the power transformer's surface was 124F at room temp of 77F.

I never had access to a HV probe for my VTVM so I always ran the Ultor control fully cw max. No problem with focus and the 6BD4 HV reg was running dark as expected. Last week I got two hi voltage spiral film resistors that added up to 940Meg. I was able to calibrate my VTVM to 4v on the 10v range when touching the probe to the 400v B++, indicating I now had a 100 to 1 voltage divider. I read the "boost voltage" at 980v without the probe and 9.7v with probe which translates to 970v or 1% low. I then touched the probe on the Ultor capacitor and got a reading of 34KV ! RCA specs the 21FBP22 at 27.5KV max. I checked the focus at 5800v. Sams and RCA sets the Ultor at 25KV, so I reduced mine to 25KV and had to refocus to 5200v but the convergence, both static and dynamic was way bad.

There is no X-Ray shielding or safety glass on this TV since 1964, when I destroyed the cabinet in going to vertical chassis. I wonder how much X-Ray I absorbed, if any? I could run the CRT between 25KV and 28KV but I must do a complete re convergence which is a real pain. Maybe the 34KV was causing the slight screen cutoff glow by activating the aluminized phosphor and reducing the ultimate black level in dark scenes ? Any suggestions?

Tom, as I think you are aware, I have a 21CT55 which has been restored. Last time I had it fired up, it needed some remedial work, and one of these days I will get back to it.

---

Andy.........I used the wrong wording "the 6BD4 HV reg was running dark as expected" in describing the glow reflected from the tube's plate when running the CRT at max HV of 34KV. Obviously, it was pulling far less current and glowed less bright than it did at minimum HV setting of less than 25KV. This is typical of all shunt regulators. At all settings, it glowed brighter when the screen went black as it should.

My main concern is how much X-Ray did I absorb during the year of running 34KV with no CRT safety glass or cabinet screen glass? Is there any documented evidence that 21in CRTs running above 30KV has resulted in injury to those persons working in close proximity for extended periods of time? If so, what was the symptoms, and prognosis?

Turn off all the lights in the room, if you glow in the dark, you're cooked.

You are probably ok if you had all the High voltage shields in place. I was working on a GE set once with the HV cage removed. It gave me a really bad headache at first. Never did that again.

---

You shouldn't worry too much unless you spent years at close range. Has there ever been any proof that Xrays from TVs can be harmful?

Check out this site for the government's take on TV X-ray emissions:

US FDA/CDRH: CDRH Consumer Information - We Want You to Know About Television Radiation
Address:http://www.fda.gov/cdrh/consumer/TVRad.html

-Steve D.

Hi Guys.
Sorry, But I do not understand this thread. Are you guys joking around?
Why would someone turn the high voltage up all the way on a vintage color set?
The high voltage should not be set over 25 kv on any round color crt made in the 60's and If the crt is something like a 21axp from the 50's it should not be set over 22 kv.if I recall correctly. Please be careful.
Ed

ED............When I first got the 21CT55 activated over a year ago, I had no way of setting the Ultor HV without a HV probe on my VTVM. I assumed the RCA engineers designed the HV portion of the CTC2B chassis to limit the HV control range to max spec for the 21AXP22 crt, somewhat above the 25KV recommended in the service manuals.Typical of my approach to design, I went for the max and left it there. Since I converted to the 21FBP22 in "64, rated at 27.5K to increase brightness, I saw no reason not to continue operating at max HV. The focus was in range and I got good convergence. Hey, it made great pictures didn't it?

Only last week when I hobbled-up a 100 to 1 HV probe and carefully calibrated it was I horrified to read 34KV Ultor or 6.5KV above RCA max spec! I immediately reduced the HV to 25KV and the screen looked terrible. I got it refocused but the convergence was way off. I then set HV to 28KV and the picture was somewhat better but convergence was still bad. Rather than getting into re convergence I simply returned HV to 34KV and posted this thread to get some expert advice. Maybe my junky HV probe is way off, but until I get a reading from a known commercial HV voltmeter I'm not going to go off screaming and mess up something that's working exceptionally well for over a year...Tom

ED............When I first got the 21CT55 activated over a year ago, I had no way of setting the Ultor HV without a HV probe on my VTVM. I assumed the RCA engineers designed the HV portion of the CTC2B chassis to limit the HV control range to max spec for the 21AXP22 crt, somewhat above the 25KV recommended in the service manuals.Typical of my approach to design, I went for the max and left it there. Since I converted to the 21FBP22 in "64, rated at 27.5K to increase brightness, I saw no reason not to continue operating at max HV. The focus was in range and I got good convergence. Hey, it made great pictures didn't it?

Only last week when I hobbled-up a 100 to 1 HV probe and carefully calibrated it was I horrified to read 34KV Ultor or 6.5KV above RCA max spec! I immediately reduced the HV to 25KV and the screen looked terrible. I got it refocused but the convergence was way off. I then set HV to 28KV and the picture was somewhat better but convergence was still bad. Rather than getting into re convergence I simply returned HV to 34KV and posted this thread to get some expert advice. Maybe my junky HV probe is way off, but until I get a reading from a known commercial HV voltmeter I'm not going to go off screaming and mess up something that's working exceptionally well for over a year...Tom

Hi Tom
Your set does have a exceptional picture and I am sorry if I sounded insulting.
It is just so dangerous running a vintage tv set with the hi voltage set to high. Why mess around with x rays if you don't have to.
Also I take it that you have not had any problems with the crt arcing inside the neck?
When you find a probe and get the time, Set the hv to 25 kv with a black screen and re converge the crt. Vintage tv repair/collectors are hard to find.
Ed

We now have a middle of the run example of the 21CT55. Was under RCA Service Company Contract till the end of the real RCA. Still in excellent operating order. Use it once or twice a week with a Zenith DTV converter box, makes very nice pictures. Not quite to your level but very nice. Very fine CRT, a new rebuilt Colorama from 1967. Was an East Tennessee set from new, a White Lily Flour Executive here in Knoxville, TN bought it new and it was his main set until he died in 1999. His daughter gave it to us afterwards knowing we would keep it maintained and occasionally used. Console cabinet also is nice unrestored original. Sold new at Proffitt's Department Stores new in Knoxville. Area department store founded in Maryville, TN (I remember them back in the day and my mom and grandmother knew D.W. Proffitt, it's founder).

---

Kent T and Dave A joined the short list of professed 21CT55 "caretakers" which include John T, Steve K, Bob G, Tom S and Steve M, the one at the Early TV Museum? All have already or are about to completely restore these rare RCA second production models to original condition, operating to original RCA specification. The obvious exception is Tom S since I have no intentions of restoring mine to original. I have no cabinet or 21AXP22 CRT, only the front panel, the CTC2B chassis and two 21FBP22 CRTs.

I decided in October 2007 to reactivate the beast after 40 years in attic storage and use it as a test bed to determine and demonstrate in photos, the picture quality this 55 year old RCA 2CT2B chassis was capable of producing. As such, it was not constrained to replicate the original circuitry in every detail or even operate to the '55 RCA spec. I jacked up the +400v B++ supply to above +420v with silicon diodes and got a horz boost of almost 1KV. I intend to start reducing the CRT Ultar HV from its present 34KV to the 28KV range while doing a full convergence at each reduction level to determine if I loose ANY picture quality.

Since I'm ruining the 21CT55 as a composite monitor, I disabled all the tuner, RK/IF and audio portions and opened all unnecessary tube 6.3v heater strings to allow the power transformer to run much cooler. I left all inactive tubes in their sockets and documented all changes for immediate reactivation. Yes, I brutalized this valuable historical item but there are at least five other 21CT55 restorations on this forum alone. I believe I've succeeded in my goal of demonstrating the 21CT55's ability of displaying exceptional picture quality.

http://s677.photobucket.com/albums/vv134/tomcomm/55%20RCA%2021CT55%20TV/?start=all[/

I do intend to refinish the surviving front panel of the original cabinet using the approach described by Bob G in his impressive restoration. I might even attempt to construct a pseudo pencil-box control panel. Tom

I guess I should jump in here with my 21CT55. It is on Steve's list but not identified as mine. Steve, permission granted.

And pix will follow. Serial #BB8801607.

I picked it up about 6 years ago at Rochester from a guy that walked up to me and asked if I wanted to buy an old color tv. Sure I said. I took a trip to his house and there it was...running. Sold for $300. I got it home and was amazed at the picture. It was soaking in color, good registration, and good convergence. The CRT is strong and original. He said it came from the home of the local RCA distributor.

But something was wrong. The color was not quite right. Turn out that either the I or Q was missing. I forget which. The pic was very orangeish. And the recap was needed.

It sat for a while in line for work. From there it took a loooong road trip to Chuck A, John Folsom and some Pony Express help from Cliff Benham. Caps, chokes, etc. done. No room here at the house for a real shop. When I gave it to Chuck, I pulled the magnet, purity ring, and yoke so he could use the yoke. I marked all of the positions on the tube neck with a Sharpie. On re-assembly, it came back as close as anyone could wish for.

On the return it had to go to storage with the cabinet as my work for the World Champion Phillies got in the way.

I retrieved it about a month ago and put it in the living room for assembly. When I did get it back in place, it worked! But it is in need of adjustment from all the changes. I can get a pic but the horizontal is slightly off and not stable. The red seems low and I have to go after that. HV is rock stable and no blooming in sight. A new problem jumped up a few days ago. On power up, the pic is good for a bit and then drops to a smear of video.

Nothing is easy about this but it lives next to my CT100 (currently at Pete Dexnis for work and comparison for his efforts) and my Philco TV123 that needs two doorknob caps. A lot of history in my living room. And a lot of furniture to walk around.

I thought I had some pix from the arrival but I cannot find them in this computer. I will try to edit this post to show the current condition such as it is.

Another survivor,

Dave A

Dave, you are blessed...I am particularly envious of the Philco. I'd rather have one than a CT100, believe it or not.

Bryan,

The TV-123 saga is the best story of the bunch. Of the six listed on Steve's site, I have had possesion of three of them. There are one or two others suspected to exist but no one can confirm them.

My first came from a retired Philco engineer who sold me a CT100 ten years ago. It was rough and I kept the chassis, CRT and sold the cabinet...the one that ended up missing at the refinishers as I remember from previous posts. He also had a 123 on his sun porch which was a greenhouse for his orchids. Whatta veneer wreck. I pulled the chassis and still have it for parts. The cabinet was beyond saving with the dampness on the porch. I took it out of charity and did not know what I had. Set #1.

Another local RCA engineer was selling his and I got it about 5 years ago. He had worked for Philco early on and got it there. He had a spare chassis also that is not included in Steve's count. The chassis' were different in that one had a beefed up rectifier on a add-on chassis. This set went to another AK collector. Set #2.

I sent that one on and it was replaced by the 123 that Chuck A documented a while back on AK. It had been a prize on a national game show and was/is in great condition. Chuck did the recap and it now awaits two small doorknobs. The big one failed and that was replaced. Now one of the others is gone and I need to get both to do it right. Any doorknob collectors out there?

It is a cantankerous beast and very hard to set gains/backgrounds to get a good pic. Set #3.

The odd thing about my 21CT55 is my mindset about it when it came back. I just threw it together and powered up and it worked. It was no different to me than a CTC7 in my mind. Just another 21" color set when you look at it from the front. I had to step back and remind myself that this is a jeeped-up CT100 and should need tender loving care to do anything at all. It lit up and now I have some work to finish. I would be curious to see how this second generation fits in with Pete's efforts on V1.0. No pressure Pete!

Stay tuned and if you are near SE PA, stop in for the tour.

I want to thank Dave A for allowing me to be the new custodian of his excess Philco 123. It is a bit scruffy, but it came with a spare chassis, so I am very much looking forward to restoring it.... one of these days.

A new problem jumped up a few days ago. On power up, the pic is good for a bit and then drops to a smear of video.

Dave AHey John Folsom: sounds just like a certain CT-100 in France, oui?

...I am very much looking forward to restoring it.... one of these days.What is it with these rare Philco's? None of them glow properly. I've been sitting on a set of restoration caps since September 2005...

Don't know how Tom's thread got on the TV-123, but they are different in that there's not much RCA influence when you check the schematic. Also, the shallow chassis is a pain to work on; just ask Chuck. Nice nonetheless to have one. BTW, as the caretakers know, TV-123 is the chassis designation; 22D5102 is the model number of the most prolific unit, a VHF-UHF mahogany model.

My reactivated 21CT55 has been operational for over 18 months with no problems except.......it takes about 30 minutes for the screen to reach acceptable size and convergence after cold morning power start up. It takes an additional 60 minutes to reach near perfect vertical linearity and final convergence suitable for critical picture capture.

I use the Digital Video Essentials' crosshatch with circles pattern to evaluate this problem with black felt pen dots on the CRT screen after the sets been running about three hours. The dots give a very good indication of circle size and linearity. A few pen lines indicate where convergence is less then perfect. Results have been consistent the last three mornings so what components has a 90 minute thermal time constant? I've already replaced the tubes and at least five capacitors in the vertical osc/amp circuitry and always keep the B++ buss set for 410v with my AC input Powerstat. Boost stays at +880v and the ultor runs about 30KV.

Hey, I'm not overly concerned and can live with the long warm up. It's not a
restored show item, just a hobby toy. Any comment or suggested fix is welcomed......Tom

Might want to check for wandering resistors. I've had a few sets that had vertical problems similar to yours, I've also had some that creep in as the set warms up. Use some freeze spray on suspect resistors and caps after the 90 min. warm-up, watch for a fast change in the picture where your dots are. Good luck with her, you have a great set!

Hey Tom,

I am having similar issues on my 55'. Warm up is slow. By that I mean from a cold dead start, convergence is WAY out, by about 1/2". As the voltages stabilize, convergence comes in very nicely. It takes a good 15 minutes from cold. Shut it down for a minute and you are back to way out again, but will come back into coinvergence faster if the set has been previously warmed up.

My linearity is very good, and HV regulates nicely at the 25KV spec. I too am running on a variac, at around 110vac, which gives me a spot on 400vdc B+ If I run off of 120 line voltage I get 437 vdc B+ and my flyback runs 20 degrees hotter. I already toasted the origanal, so I am being most carefull to not destroy this one. Running at 400vdc the flyback operates at about 125 degrees F after several hours of run time and also with the dog house panels removed. After I have the thing running to my satisfaction, I will reinstall the dog house panels and install a muffin fan to keep the dog house internals cool.

I would be interested in knowing what your flyback temp is after you run for several hours, just for comparison sake. I use a DMM with a thermister probe to take temp readings. I of course do it with the set turned off and the door knobs discharged. I place the probe on the surface of the primary windings and hold it there till the temp reading stabilizes. I like 125 degrees F. It seems to me to be a safe operating temp.

Been trying to run down an intermitant flashing brightness issue, but haven't had much time to trouble shoot lately. I am pretty sure if I stick at it long enough I will locate the gremlins. that is, if I live long enough :-)

I like Mark's suggestion to try freeze spray on resistors to see if I can cause the convergence to drift out. Maybe I can find a resistor that is overheating and changing value as the set warms up. Being as convergence is done with the set warmed up, it would be logical that when the set cools down it would be out of convergence if a resistor is changing value as it heat up. I just ordered up 3 cans of freeze spray. I found it online for only 4.99/can at http://www.southernhillscomputer.com/index.html some places wanted $10 per can. The stuff is R134a refrigerant. I am epa licensed to do refrigeration repair and buy this stuff in 30 pound drums normally for repairing air conditioning systems, but 30 pound drums are a bit to large for squirting resistors with :-)

Bob

Have you replaced the selenium rectifiers and checked all the filter caps? Although I haven't personally had trouble with those huge seleniums in the CT-100/21CT55, I know they're capable of trouble like you're having. Fairly simple power supply. However, it might be a benefit to have that ultra-slow warmup... I think most failures of other parts happen on startup surge; when the B+ is highest (in solid state rectified sets like this), and the tube filaments are still cold and the power supply is running hog-wild unloaded. Come to think of it, maybe let it be, as long as it isn't a slow-forming filter cap which may be pulling a ton of current. An AC ammeter would check that too.

Charles

Yep, power supply is all reworked. Seleniums are just ther for show now. Every can in the set has been re-stuffed with bran new axial lead caps.

I have monitored voltages during the warm up, but I do not find any significant variation during the period that it takes the convergence to stabilize.

Steve Kissinger saw it and said the he dosent have this symptom on his recapped 55' . I could live with it but it is a symptom I don't like when I wish to turn the set on for a few minutes to demo it to someone. It would be nice for convergence to come up right away so the picture would be watchable in a reasonable amount of time.

I even re-hooked up the old seleniums just to see what would happen. I got a very substandard 372vdc when opperating at 120vac line. The set runs much better on the silicon diodes, so I am convinced that the old seleniums cause sub par performance.

Bob

Thanks for the replies regarding my warm up problem. I've been running silicon diodes in place of the seleniums from the first time I fired up the 55 and got only 390v of B++. Lost a lot of heat in the bargain. I replaced the rectifier’s 80uf big can electrolytic with a 100uf at 475v. The B++ goes to 455v at turn on and settles back to 410V operating. A Powerstat manually keeps the AC at 113vac resulting in a B++ of 410v which produces exactly +900v of boost and 30kv of ultor.

Since the boost voltage is used in the vertical oscillator height control, any change in boost voltage or the resistancs of the 2.5meg height control, both height and linearity greatly effects screen's appearance but more importantly vertical convergence accuracy! The height and linearity are both controlled with a cheap open terminal dual pot. The 5k linearity portion was open originally and I replaced it with a single pot mounted in a new control panel hole. When I hit the surviving height pot with Quick Freeze, it collapsed the vertical screen and destroyed vertical hold. As it dried out the screen circle almost returned to normal. I replaced it with a sealed military grade Allen Bradly 2.5meg pot I had from the ‘50s. When I adjusted it to the circle dots, linearity was restored and convergence improved significantly. Was this the fix? Time will tell when I fire the 55 tomorrow morning. All Hail Marys are welcomed.

I started using Quick Freeze on the rest of the vertical circuit resistors and caps but didn't finish yet since I was running my last can out. No further temp sensitivity so far. I took Bob’s suggestion and ordered five cans for the same $12 shipping as three, from Southern Hills. My nearest electronics store was a long trip and they wanted $8 a can. Santa Ynez is great to live in but major stores are at least 60 miles RT in any direction. ....Tom

Glad you're getting close, let us know how she runs tomorrow! That dang freeze spray has found many a gremlin for me. Good stuff.......

The replacement of the height pot and .047uf amp feedback cap made a major improvement in vertical height and linearity stability. The sequential pictures show the cross hatch and circle pattern improving during warm up. Although better, it is still entirely too long a time for performance demonstration.
The black felt pen dots applied directly to the CRT screen represents the ideal circle locations and are very useful in judging the results of any circuit modification. My 55 can be expected to present a useful screen for casual viewing in about 10min after turn-on and reach maximum picture quality for critical screen shots in about 1hr. Convergence has not been optimized since vertical performance is the issue here.

Is my 55 unique with this problem or do all CTC2B chassis and maybe all RCA CTVs up thru CTC10 have this same problem to some extent? I would like to see sequential screen shots of member's early RCA's during warm-up. Ideally they would use the same DVE DVD cross hatch and circle pattern I use, and would apply the felt pen dots directly to the CRT glass for reference.....Tom

Bob G........Somehow I didn't realize you were the "Bob" of the recent, most impressive full restoration of all 21CT55s. Since you did a complete recap I would expect yours to have the least problem with warm-up drift. I assume you Quick Freeze'd all resistors in both deflection systems and the complete convergence chassis? I can imagine your frustration when you fire-up your beautiful 55 for some TV-wise visitor and it comes up greatly miss-converged. I have the same problem but I never have demonstrated my 55 to any knowledgeable visitor, so waiting 30 to 60 minutes warm-up before taking critical screen shots is no big deal. I've asked this forum's members that have early RCA tube CTVs if they had similar problems and received zero replies. Must be you and I have a unique problem or others are unaware they have a problem or have little interest in the subject?

I checked my power transformer and horizontal output transformer tempts after over 3 hours operation on 113vac mains input on a hot day. The B++ was 410v, Boost was 900v and ultor was 30kv. The horz output tube input control was set for minimum drive and the horz B++ current was 320ma, horz output transformer was 113deg and the power transformer was 140deg.

I will continue freezing all critical resistors and caps looking for sensitivities as soon as my five cans of quick freeze arrives next week. Of course I will report any interesting results.....Tom

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I've asked this forum's members that have early RCA tube CTVs if they had similar problems... As I am sure everyone is aware, the CTC2B chassis is an outgrowth of the CTC2; the two chassis have far more similarities than differences.

When I need to view my CT-100 (CTC2 chassis) critically, I never do so without a bare minimum of 30 minutes warm-up, with one hour typical. In particular, fine color balance is not achieved without the warm-up time. I often wonder if a 'time-warp-acquired' set of just-manufactured tubes from RCA Harrison would shorten the warm-up requirement. My sense is that the 55-year-old 6AN8's and 12BH7's require more time to stabilize than when they were new, even though the time on them is not great.

Pete

Hi Tom,

Thanks for the info on the HO trans temp and B+ current. Yours seems to be running nice and cool. That gives me a good benchmark to shoot for. I just got back from a vacation and my freez spray has arrived, so I will try and find some time to look for temp drifting resistors this week to see if I can nail down the large shift in convergence at startup. The funny thing is that after half an hour of running, when the convergence has stabilized, I can turn the set off for 15 seconds or so and the convergence drift will re-occur. But it will re-stabilize in about 2 minutes.

John Folsom has told me that I should replace the flat green power resistors. John says that these type power resistors are known for being a problem. That is the next thing I will try.

Thanks again for the data on temp and voltage/current readings. I will post again as progress is being made.

Bob G.

The original flat green power resistors are rumored to be a little intermittent, causing things to flash and change suddenly. They do not, however, drift wit temperature.

Had to replace those green power resistors on our example before it worked well consistently. A known intermittent part. Beautiful set and landmark engineering for the era. Superb picture with that vintage RCA accurate lollipop color. One of the best pictures I ever saw on a color TV set after the pain of getting it right.

I have this continuing problem with my 21CT55 after a year of operation.With ext video input from the DVE test DVD at blacker-then-black video level input and the contrast and brightness controls fully CCW, I observe a uniform, non-raster, very low-level white glow over the entire screen. This is only obvious in a totally dark lab on the RCA but not on the Sony monitors operating on the same video.

During critical PQ evaluation comparisons with the Sony with no room lights, this glow detracts from the absolute black of the RCA on demo DVE's video relative to the Sony. This is disturbing to me since I never watch LCD TV and suspect my RCA crt's black presentation is similar...yuk!

What to do?? I've tried a few diagnostics:

(1) I determined the 21FBP22A is driven well into cutoff by at least 120vdc.
Besides, the glow is not scan-line defined as if it was going thru gun optics.

(2) By under-scanning the crt with misadjusting the vertical linearity control,
the glow is confined crudely to the raster area of the crt but totally out of
focus. So its effected by the deflection yoke but not the gun optics?

(3) Could this be caused by secundary emmission from the gun elements?

(4) Could it be caused by X-RAY excitation of the gun elements? I am running an ultor of 30kv. The 21FBP22 is rated for 27.5kv so I reduced it to a min of 22.5kv with absolutely no change in the glow intensity.

(5) How about a small air leak? No violet glow in the gun assembly.

(6) I pulled off the crt socket and turned the power on and let the ultor come up. No screen glow so I pressed the crt socket back on. No immediate glow as the crt heaters came up to temp, still no glow. After about 3min running, a glow was barely noticeable. It got progressively brighter until after about 10 min it was at maximum. I directed a fan at the crt neck attempting to cool it but it made no difference.

Question: Is this low level glow I have on my 21FBP22A a common phenomenon observed on many early roundys but only noticed on very dark scenes in totally dark rooms? Since I have only one operational roundy and have not observed another roundy in 30yrs I have no way of finding out. I would be very grateful for any worthwhile replys regarding the cause of this glow and the prevalence of this abnormality in other forum member's roundys.
......Tom

I have this continuing problem with my 21CT55 after a year of operation.With ext video input from the DVE test DVD at blacker-then-black video level input and the contrast and brightness controls fully CCW, I observe a uniform, non-raster, very low-level white glow over the entire screen. This is only obvious in a totally dark lab on the RCA but not on the Sony monitors operating on the same video.

During critical PQ evaluation comparisons with the Sony with no room lights, this glow detracts from the absolute black of the RCA on demo DVE's video relative to the Sony. This is disturbing to me since I never watch LCD TV and suspect my RCA crt's black presentation is similar...yuk!

What to do?? I've tried a few diagnostics:

(1) I determined the 21FBP22A is driven well into cutoff by at least 120vdc.
Besides, the glow is not scan-line defined as if it was going thru gun optics.

(2) By under-scanning the crt with misadjusting the vertical linearity control,
the glow is confined crudely to the raster area of the crt but totally out of
focus. So its effected by the deflection yoke but not the gun optics?

(3) Could this be caused by secundary emmission from the gun elements?

(4) Could it be caused by X-RAY excitation of the gun elements? I am running an ultor of 30kv. The 21FBP22 is rated for 27.5kv so I reduced it to a min of 22.5kv with absolutely no change in the glow intensity.

(5) How about a small air leak? No violet glow in the gun assembly.

(6) I pulled off the crt socket and turned the power on and let the ultor come up. No screen glow so I pressed the crt socket back on. No immediate glow as the crt heaters came up to temp, still no glow. After about 3min running, a glow was barely noticeable. It got progressively brighter until after about 10 min it was at maximum. I directed a fan at the crt neck attempting to cool it but it made no difference.

Question: Is this low level glow I have on my 21FBP22A a common phenomenon observed on many early roundys but only noticed on very dark scenes in totally dark rooms? Since I have only one operational roundy and have not observed another roundy in 30yrs I have no way of finding out. I would be very grateful for any worthwhile replys regarding the cause of this glow and the prevalence of this abnormality in other forum member's roundys.
Maybe Scottie is knowledgeable? Anyone know him personally?......Tom

I have seen the glow on modern set's and it was the screen voltage set to high, But I would think you would see retrace. Try turning down the screen controls and see if your problem goes away. I have never seen this on my round color sets and I use them almost every day.
Ed

It shows a warm-up effect, so it is not field emission, which would come on immediately. It's not secondary emission or x rays either, because the normal beam current is off. My only guess is that it could be thermal emission from G1 after it gets heated up. I second Ed's note to see if changing G2 voltage affects it. I have no idea if this was common.

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A web search shows there were a number of papers written on techniques of constructing grids to suppress unwanted emission,which could come from evaporation of cathode material onto the grid.

I contacted a crt rebuilder that was mentioned on the ETF site called Magnaview. Talked to Earl who has been rebuilding roundys for 25 years. When I briefly described my cutoff glow phanomination he immediately identified it as cathode contamination of the grid which produces unfocused electron emission when the grid gets heated by the cathode. This substantiates the speculation of John F, Wayne B and Andy. Earl stated emphatically that most all roundys have this glow after 10 years of operation. Its something we all have to live with as we and our roundys get older, something like arthritis.

I requested the forum members to test their roundys with a very simple procedure (even a caveman could do it). Activate TV with brightness, contrast and chroma at full ccw and view in a total blackout room for greater than 15 minutes. Got one reply that no glow was observed after 20 minutes. His crt was a very recent regunned 21FBP22 with no chance of any cathode buildup on its new grid. No one else reported observing the low level cut-off glow or if they did, would rather not comment??

I talked to Scotty about getting mine rebuilt with new original guns. He says no problem, $400 with my dud. He claims he has never observed my "glow" or even heard of the problem, but then he only scrutinizes his newly reguned rebuilts and I doubt in a total blackout room.

My 21FBP22 has not been rebuilt or had a brightener on it. It has good emission on all guns as long as the heaters run above 6.5vrms but falls off rapidly as I drop below 6.3vrms so the cathodes are pretty well depleted, near end-of life. I am now running a switched brightener which supplies 6vrms normal or 7.5vrms boosted at the crt. each gun's emission is way good and well balanced., no change in the glow intensity though.

Really the only time I notice the glow is at the start of the Digital Video Essentials test DVD during the "sunrise out of total night darkness" scene at the start of the video demo. This is a great DVD for setting up, evaluating and comparing the PQ of the early 50s 21CT55 with the 80s and 90s Sony monitors with comb filters. When they all look virtually the same, you know the roundy's PQ is truly optimized.....Tom

I just sent our second 21CT55 to Russia for a TV documentary. It has a chassis that had been working well. The day the shippers arrived, the set developed two independent problems - both due to flat power resistors that had opened up. I would recommend changing them all.

Those flat power resistors are know to cause trouble in 21CT55s and CT100s.

Follow up report:

tested my RCA Cheltenham CTC-4, which has what I think is an original CRT in it. The CRT has the rCA logo on the base, and is engraved "21AXP22A/21AXP22". The painted on date code is unreadable.

With the brightness an contrast controls turned down, and the 3 G1 grids biased to ground potential, there is absolutely NO glow in a ptich black room, after 45 minutes of operation at 25KV ultor voltage.

This seems to confirm the data from Tom and Wayne that says Tom's glow is due to cathode contamination of the G1 grid. Tom, you need to find a good 21AXP22 for your 21CT55 chassis so it can be returned to it "proper" configuration! :yes:

If it were me I would try to locate a really dead dud to send for rebuilding. Seems ashame to rebuild one that is still in pretty good shape. Just my opinion.

I know I have seen such a glow on some sets, though off hand I can't say just which ones. Mostly noticed when doing the setup procedure and all guns are biased off-yet I still have a faint glow on the screen.

As it stands now, Bob G and Wayne B tests "noglow" but have recent reguned 21AXP22s, no chance of grid contamination from cathode deposits. John F's tests noglow from his original 21AXP22 in his CTC4! This crt is at least 10 years older than my 21FBP22A and should be more contaminated than mine, right. Pete D will test his 15GP22 just as soon as he gets it running again. I need more glow testing of non-reguned roundys like mine.

So out of four roundys tested, my 21FBP22A is the only "glower". Has it been this way when I got it 40 years ago but I never noticed or have I abused it by running over 32kv ultor the last couple of years? Anyway, the glow is only noticeable during very dark scenes when viewed in a totally dark room. I can live with this considering the only fix is to find a known good 21FB cheap (ha) or let Scotty rebuild one for $400 plus a couple hundred two-way risky shipping.

Rebuilding a 21AXP22 if I could find a core is out of the question. There would be the additional core charge and I would have to find an ultor hv boot or hobble up something and I'd be back to 1964 when I converted over to the brighter 21FBP22 in the first place. My 21CT55 is not a restoration, picture quality is the objective here, not proper configuration.

If I get desperate, I can always install my spare 21FBP22 green screen sulfide and hope its been spared the glow of the present gray screen 21FBP22A rare-earth..........Tom

My understanding is that grid emission is caused by evaporated barium from the cathode ending up on the inside of the grid cup, where it can become an emission source, when the grid reaches a certain temperature. Higher than normal cathode temperature can cause the evaporation of the barium as well as contribute to a hotter than normal grid cup temperature. Is the crt heater voltage running high in this set?

jr

When I bought my 21CT55 in ’64 it had no booster on its 21AXP22. I converted it to a 21FBP22 when I compared its brightness to my CTC4 which I converted to a 21FB a few months earlier. I have never run a booster on the present 21FB or rejuvenated it, since it has always and still is very bright. I reactivated the 21CT55 about 1.5 years ago and ran the ultor at max since I had no HV vtvm probe and everything seemed fine. I have a Powerstat on the mains input in order to limit the B++ at 410v with the silicon rectifiers that replaced the big seleniums. This dropped the heaters from 6.4vrms to 5.95vrms so no over heating of the crt cathodes here.

I became aware of the below cutoff full screen glow a few months ago but since it only was annoying on very dark scenes during no light night viewing I tended to ignore it. From a cold start, the glow becomes barely noticeable in about 3 minutes and steadily gets brighter, reaching max in about 10 minutes. A relatively long time constant for the small masses of the crt gun assembly. Crt grid contamination from the cathode seems the most logical explanation for the glow, but I need more input from forum members that are running non reguned roundys…………Tom

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3 to 10 minutes (sometimes as much as 30) seems to be in the ballpark for the grid structure to heat up. Remember we are in a vacuum here, so there is NO convection, little conduction, because the cathode is mounted on an insulator, so the grid cup is heated mostly by thermal radiation from the hot cathode (about 750 degrees C). If it is grid emission from G1, then lowering the G2s (R,G,B screen controls) should decrease the "background" that you observe when the set is warm.

jr

Are the heaters of all the small tubes in the set also running at 5.95 vrms? could cause a warm-up time problem?

I have a few roundies with their original but strong CRTs, I'll check them out to see what they do and report back later.

Well its been almost a month since I first reported to this forum the "cut-off glow" displayed on my original 21FBP22A and I described a simple test to determine if other members had similar conditions. So far I have received 4 replies, hardly an overwhelming response: 2 recent rebuilds, no glow, 2 originals, no glow. Mine is an anomaly, possibly caused by a shop poltergeist?

I have assembled a new presentation of relative picture quality between my '54 21CT55 and a '92 Sony KV27TS27 with comb filter. All pics are 1024 X 768 and should fill the width of most computer monitors. Any differences in PQ is readily apparent on these larger displays. I use Outlook Express to produce an .....ENL file that permits comparisons by slewing between adjacent inserted pictures.

Anyone interested in viewing these latest Picture Quality comparisons can send me an email to this address: [email protected]

I will reply to you, using the BCC window, with a file attachment that will play in your Outlook.......Tom

Recently I questioned the reasons why my 1954 RCA 21CT55 with its first full NTSC spected CTC2B chassis and the last roundy 21FBP22A crt produced picture quality almost comparable with my solid-state, comb-filter 1984 and 1992 Sonys. I checked all the RCA schematics from the CTC4 up to the CTC38, tube types and also the all solid-state CTC40 of 1970. All of them have narrow bw chroma processing and hi level crt luminance/chroma combining. Did RCA ever go back to wb IQ video processing? The dramatic difference in picture quality between wb IQ and nb R-Y/B-Y was obvious to me in 1964 as related in my first AK 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 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 which 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 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 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…….

I have assembled a Flickr photo post: http://www.flickr.com/photos/tomcomm/

After selecting a thumbnail, click on “all sizes” above picture to enlarge to full screen. Two clicks of the Browser’s “Back “ returns to thumbnails.

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I believe RCA made a chassis in the early 80's with I Q processing. I think it was a CTC13X chassis, but I forget the exact chassis number.

RCA developed a clever way to drive the required I delay line single ended, thus saving a pin on the analog IC. However, when I measured the performance of this chassis for comparison with Zenith sets of the time, the I channel high frequency response was low, not much better than the residual high frequency chroma in the Zenith narrowband demods. The reason, I believe, is that it was too difficult to get the required flat and phase-distortion-free chroma response even in the Q channel, partly due to the difficulty of making an IF that was both sharp-cutoff at the sound carrier and phase-distortion free. So, I think RCA turned the I channel high frequencies down (or didn't peak them to normal level) to avoid annoying hue effects on edges. The other part of the problem was that the NTSC never specified the encoder Q filter closely enough. Some Q filters that would meet the NTSC/FCC spec would still leave visible Q sidebands beyond +/-0.5 MHz that would be unbalanced by the sound carrier trap in the receiver. By the time this RCA set was around, it was known how to make good encoder Q filters that would have a zero at 4.5 MHz and symmetrically at 2.7 MHz, but of course the specs would never be changed in the thousands of encoders out there.

Experiments I did with "ideal" I/Q pictures (using baseband filters and never going to RF) showed that the increased saturation on small bright details and increased sharpness of red roses, barns and rocks was noticeable in side by side comparisons, but also visible were things like the edges of typical yellow movie-title letters turning orange. With a 27 inch or larger set, you couldn't keep people from getting too close, the way a 12-inch console would. Zenith concluded that there was no way to get a good compromise between visibility of red details and visibility of artifacts, and that it would be hard to actually show any of this to customers. If you couldn't turn up the red detail, there was no point in going to I/Q demodulation.

Here's an example - look at the differnce between the vertical and horizontal strokes of the letter t in Beatles. Unfortunately, I can't turn off the dot crawl in this simulation, whihc would be less visible in reality due to alternating phase from frame to frame. The dot crawl (with a simple chroma trap in the luminance) will generally fall in the same area as the red-orangish discoloration of the yellow.

It should also be visible in the vertical vs. horizontal strokes of the B. I find I have to zoom out quite a bit, until the image is about 1.5 inches wide (at about 15 or 20 inches viewing distance), before the discoloration becomes really less noticeable. This shows that the ability to get away with less chroma bandwidth than luma and use narrower Q bandwidth than I, does not have a sharp dependance on viewing distance, but also depends on the viewer not having an original to refer to. When home computers came out however, the lack of chroma resolution on small text and artificial objects with edges but no texture and possibly little brightness contrast made the failings of composite video obvious.

The exact chassis number that uses I and Q is the CTC-121, mine's from '84 and has a beautiful picture.

I just ran some pictures of roses against dark green foliage through the simulation to show what the extra I bandwidth does in this case:


Original full bandwidth RGB:
http://farm3.static.flickr.com/2716/4279831511_3c6bb86fb2_o.jpg


Wideband I (and narrow Q, of course):
http://farm5.static.flickr.com/4013/4280576116_9a8e1af077_o.jpg

Narrowband I and Q (equivalent to R-Y/B-Y or X, Z or any other narrow equiband demodulation):
http://farm5.static.flickr.com/4046/4280576062_80e5c7b7d3_o.jpg

the wideband I:
http://farm5.static.flickr.com/4003/4280576028_d521d13bfb_o.jpg

the narrow band I:
http://farm3.static.flickr.com/2705/4280576000_889d23b529_o.jpg

the Q:
http://farm5.static.flickr.com/4046/4279831337_5a4d9ca17a_o.jpg

On my little Eee netbook, the loss of detail in the roses is subtle but real; neat simulation.

What you should do is save the images so you can use your favorite viewer, then zoom in until the image is the same size as on a 25 inch diagonal tube. The differences will be much more apparent, just as they would in real viewing.

Here's a try at posting an animated gif of the differences:

http://farm5.static.flickr.com/4027/4280697112_f94994592d_o.gif

Edit: It worked! Sometimes I amaze myself!

Great simulations Wayne! I know nothing regarding Photoshop Pro, but their filter capabilities must be awesome. My little Photo Impact’s custom filters only effect a 5 X 5 pixel zone, resulting in an overall softening or other distortions. No way can it filter color content of red, blue or green components. Obviously, Photoshop is capable of simulating the color separation of a dicroic filter into their primary colors. Developing I and Q components from the 32bit chroma of each pixel and combining them in quadrature and then bandpass filtering them to produce perfect NTSC baseband bit streams. Is this a canned program within Photoshop or did you develop this NTSC simulation on your own? Whatever, you certainly are an expert in TV system simulations.

When you conducted comparisons of the 1984 RCA solid state I, Q, WB receiver with the current Zenith R-Y, B-Y, NB receivers you noticed improvement in the RCA’s red detail, but also the presence of quad crossover distortion artifacts along color transition edges, The 1954 IRE Color TV issue had a 1953 paper by Hazeltine on the very subject of “Quadrature Cross Talk in NTSC Color TV”. Seems this problem was solved in the fully compliant NTSC WB, IQ implementation of RCA’s first production models., the CT 100 and 21CT55, using the CTC2/B chassis. That same IRE issue described a true laboratory standard color receiver built by Sylvania in 1953 which was fully NTSC compliant and very similar to the RCA CTC2/B WB IQ decoder. It had an additional NB R-Y, B-y decoder similar to the RCA CTC4 thru CTC38 at least. These decoders could be switched to the same 15in CRT display for picture quality comparisons. Regarding the NB R-Y, B-Y , their comment was "Although this method gives the desired result, much detail is lost due to narrow-band operation”. I have to assume if any cross-talk artifacts were present in the lab standatd WB, IQ receiver it would have been well reported.

The built-in filters in Photoshop are not up to this job. I had to write my own using an authoring program called "Filtermeister." The filters are phase-linear FIR filters designed for the proper I, Q, and chroma trap bandwidth. There is also a sharp cutoff lowpass to simulate the IF amplifier.

The modulation and demodulation is done by assuming that the pixels fall exactly on 57 degrees (I), 147 degrees (Q), 237 degrees (-I), and 327 degrees (-Q). This results in a 720x540 4x3 square-pixel image, close enought to the real NTSC sampled values for illustration.

The irony of this thread is that all things digital in 2010 are being used to recreate the missing information of the color analog world in 1954. And probably with more information than they had at hand.

Keep it up because we all become more informed and more educated...digital or analog.

Dave A

Here's a try at posting an animated gif of the differences:

...

Edit: It worked! Sometimes I amaze myself!

And us! :thmbsp:

Still pondering the relative picture quality of the NTSC spec’ed WB IQ chroma demodulation used in the RCA CTC2/B chassis and the simplified NB R-Y B-Y chroma demodulation used in all other RCA CTVs thru 1980 at least. When did any CTV return to WB IQ if ever! My two premium Diamond-view Mitsubishis of 1988 and 1996 both have comb filters but I can’t identify WB IQ in either. Admittedly I have very few detailed schematics of my Sonys but both 1982 and 1992 jungle chips identify R-Y, B-Y demodulators, no mention of IQ anything. So does anyone know for sure any modern CTVs that for sure use WB IQ processing? My 1988 13in Sony RVM 1344 Pro Monitor must surely use WB IQ demodulators along with it’s comb filter, the direct screen is awesome. We’re there ever fully digital implemented CTV, AD rf inputs thru all digital demods to LCDs before the end of NTSC? How about the high-end ATSC to NTSC converter boxes that outputted component analog video or the best DVD players, did they encode MPEG to NTSC in WB IQ? It seems that NTSC spec’ed WB IQ started and ended with the RCA CTC2/B chassis, or am I wrong……..Tom

AS stated above, the RCA CTC-121 was the only consumer set that revived IQ demodulation. DVD players, DTV converters, etc, all use equiband modulation, but it may be wider band than the standard Q channel. If you input this to your TV as baseband composite, or especially S-video, you may get some chroma bandwidth improvement. However, the best chroma bandwidth by far comes from using the component Y Pr Pb output of such devices if they have them, and skip the chroma mod/demod process altogether.

No idea if your 1988 13in Sony RVM 1344 Pro Monitor used IQ demods. Tektronix monitors did not. In fact, the smaller screen Tek monitors had a strictly limited luma bandwidth also to prevent moire patterns due to chroma dots beating with the relatively coarse screen stripes. TV station engineers loved them - the pictures looked CLEAN because they also hid any garbage in the upper end of the luma signal.

By the way, I know someone who worked on a super high-res sharp focus NTSC monitor for Tek. The project was dropped when they saw that it made NTSC pictures look awful when you had full-contrast resolution of all the luma artifacts and the scanning lines with black spaces in between.

I don't have the service notes at hand at the moment, but I believe my CTC-136B has WB IQ demod, using a chipset by NEC. I'll dig out the folder and take a look when I can.
Thanks for the comparison.
Kevin

So far only the CTC 121 and CTC136B were suspected to have used WB IQ chroma demodulators. Wayne states he evaluated the performance of a RCA CTC13X that had WB IQ demodulators but gave no details of its implementation; did it use a NEC IC? A whole bunch of guys say they have or had either CTC 136Bs or the CTC121s which also is claimed to have WB IQ processing:
CTC136B stromberg67 Kevin
CTC121 zenithfan1 Mark, waltchan, zenith2123, wa2ise, nrx37, blast
Surely at least one of these has a schematic or other documentation that definitely proves the CTC136B or CTC121 used WB IQ and how it was implemented. Since I have a CTC2B open on the bench I would appreciate any information why RCA tried WB IQ on only a couple of CTVs and quickly dropped it. Thanks, Tom

I don't know which chassis number I looked at. I only ever knew of one with IQ chroma, and I don't know who actually manufactured the IC, but I do recall that some very clever analog design was done by RCA to minimize the pin count.

I did my own test to see improvement in picture using the 3 seperate color outputs from a DVD fed into a digital widescreen projector. Compared single composite video and then three seperate colors, the three colrs image had slightly more depth in color, shading. The detail differance was minimal. High end Proxima PJ w/ full resolution capibilities of a DVD slightly displaying their differences displaying a 15 to 18 ft screen.

NTSC really shows it's full potential to be in the area somewhat near wideband color in quality. The only real way is for the Museum, OR one of the old color TV gurus who can compare a wide band color to narrow band sets side by side from the same vintage.

Waiting for Stromberg67 to come up with a schematic. The only references to NEC IQ demods on the web are for their digital demodulator chip (NOT a chroma demodulator), but it could have been.

I just did a comparison of component to S-video using one of the excellent Disney DVDs extra feature gallery of artwork stills, and find the differences are quite small. They probably are greater going in composite and still greater going in RF, but I don't have time to do all that right now.

The Kloss Videobeam 1000 projector from the early 1970s had full I&Q demod. I guess Henry thought it would be necessary with a 54 inch diaginal screen. A friend has one of these and a manual. I don't know if it was done with ICs or discrete transistors. Cliff

Stromberg67 of Rectangle and Solid State posted this, check it out:
[QUOTE]Hi Folks: I have the SAMS for my CTC-133B open in front of me, and the chip designated "U 700" , a 42-pin DIP, shows I and Q demodulators and amps, and the integration of luma and chroma signals on the chip.[QUOTE

Kevin.........That CTC133B schematic is a great find! The RCA number 176225 crosses with Hitachi, maybe its the same chip? The fact that it combines luma and chroma at low levels instead of at the CRT is great. It's probably why you get such great color detail. I bet there's a lot of inductors and caps around the chip to do all the required filtering in analog. Is there any way you can scan or photo the small schematic portion around the chroma demod chip? Can you PM me for my email address. If the chip is available ($5.00), it would be fun to attempt to build up the circuitry and try it out. Thanks, Tom

Perhaps WB IQ didn't work so well after the CTC2/B was due to the fact the later CTV had fewer IF stages than the original six! When they got down to three stages they couldn't get the flat response and precise uniform phase delay required for WB IQ without artifacts, so they stuck with NB R-Y B-Y? Rediscovering WB IQ really fascinates me and others. Sort of cultish,eh?......Tom

I checked all the RCAs from CTC4 to CTC20. the CTC4 had a tuner IF plus three chassis IF amps. the CTC5 had same 4 IFs. The CTC7 had no tuner IF and 3 chassis IF, 3 total. All the rest to CTC20 remained at 3 total IF amps verses 6 IF amps of the CTC2/Bs!. No wonder WB IQ was wasted on these last tube CTVs.......Tom

So, let me see if I'm following this correctly. Y'all are saying that the CTC2 (CT-100) and CTC2B (21CT55) were the only early sets that used wide-band I and Q demodulation?

Was the change to R-Y/B-Y done just for cost savings? Or possibly the average viewer wouldn't appreciate the difference, anyway . . . ?

Just curious.

Phil Nelson

RCA was not the only manufacturer to field a wideband 15" color TV in 1954. The Admiral, sylvania and CBS 15" sets are wideband I/O sets. There may be others, but I cannot recall for certain. The Westinghouse, Sears, Hoffman, GE, Motorola, and Zenith are narrowband.

the changes in circuit design were definitely aimed at cost savings. The CTC-5 came in two versions, with the Deluxe being cost reduced from the CTC-2B, and the Super being even more cost reduced. They apparently found that some of the shortcuts in the Super were going too far, as later chassis used a number of circuits first tried in the Deluxe.

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.

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

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.

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?

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........TomActually, 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

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.

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.

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.

I believe RCA made a chassis in the early 80's with I Q processing. I think it was a CTC13X chassis, but I forget the exact chassis number.

My CTC-136B is wide-band, manufactured in 1986, and has the I-Q chipset. I'll look at the SAMS to see about the single-ended I delay line. I'm getting much from the topic of the "glow" that may be due to grid contamination. I'll see if I can find an hour or more later tonight to fire up my 4, and look for the glow. Thanks for all the info!
Kevin

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!

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.

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.

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,

Tom-

That is a very interesting test. Are you able to set the camera into a completely "manual" mode, so it doesn't do any type of color balancing on its own? If so, do you also need to pick a starting color-balance mode? I know mine has several settings for modes but I have not studied its operation very much.

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.

This is still a little suspicious. Getting purer colors when the drive is turned up could indicate that the black level is a little high or there are reflections of room light. This would be a valid test of how the tube is set up and viewed, but not necessarily the characteristics of the red phosphor color alone. To get the comparison of the pure phosphor colors you need to do two things:
1) take the picture in a completely dark room, making sure there are no reflections (like from your shirt)
2) turn up the color control and adjust the tint if necessary to make sure only the red beam is on and the other two beams are completely cut off.
2b) Since the color demodulator may include color corrections that deliberately make the primary bars impure, you may need to readjust the tint individually for each primary color if you want to measure the green and blue also.

Why not use one of the TV tools with 'gun killers'? They include a feature which shunts the guns grids through a 100k resistor at the flip of a switch, though you could do it with clips as well.

Some misconceptions regarding this phosphor spectral analysis procedure seems to exist. My objective was to evaluate its potential to determine the relative spectral purity of the original NTSC spec’d dim CRTs versus the later, brighter CRTs e.g. 21FBP22A:
1) Only previous informal archive screenshot JPGs were used. No rigorous colorbar setup was used regarding black level, chroma level or luminance (contrast) level. All screenshots were taken in total darkness. Purity and focus were always good.
2) The playback LCD monitor is used only to direct the location of the virtual pointer over the JPG image. It’s chroma characteristics contributes nothing to the JPG phosphor contamination determination. Only the Canon S40 sensor can influence the results.
What is needed now is member postings to this thread their quality colorbar screenshots of their 15GP22, 21CYP22, gray 21AXP22A , green 21AXP22 , green 21FBP22 and gray 21FBP22A all taken in total darkness. Thanks for your interest and cooperation

My CTC-136B is wide-band, manufactured in 1986, and has the I-Q chipset. I'll look at the SAMS to see about the single-ended I delay line. I'm getting much from the topic of the "glow" that may be due to grid contamination. I'll see if I can find an hour or more later tonight to fire up my 4, and look for the glow. Thanks for all the info!
Kevin

Just poking around and saw this thread. I was designing televisions at RCA in Indianapolis when the CTC-136 was made. While the Sanyo IC has I/Q demodulation it did not have the wide I channel that was only used in the CTC-131 and CTC-132. I seem to remember the short lived CTC-133 used the same RCA designed chip but the wide I feature was not incorporated. The CTC-121 was the first 25" in the space of a 19" but did not have the Wide I processing..

In those days RCA designed all the IC's in their receivers. I designed the deflection processor in the CTC-146. RCA in Sommerville was the first source and Hitachi was the second source. I remember having to tweak some resistors in the 32 h input circuit as hitachi's transistors behaved a little
different than RCA's.

The CTC-131 chip set included a wide I demodulator and a kine drive IC with auto kine bias. Those were the days....

The CTC-135/136 was a low end chassis designed by RCA Taiwan and overseen by Indianapolis. It used a Sanyo chip that was modified to meet RCA's specs.

I wish i could remember why the Wide I was removed from the CTC-133. Seems there was some reason.. I may have some of those IC's around if I can find them!

JBL-1, my previous post stated that I had a CTC-136B, but it's a 133B. There's a 135 in my daughter's bedroom, and it's not bad for a little Taiwan TV.:yes:
I wasn't aware that the I wasn't wide-band in the 133. The color resolution on my set is really good when compared to the narrow band TV's in the house, and it will reproduce small detail in color, oranges and cyans, etc, but a really good picture. Interesting information, and I thank you for it. I'll look for more info on this and similar chassis where ever I can find it.
Kevin

JBL_1, it's great to hear from someone involved with those sets.

The wideband IC demods were discussed in at least a couple a couple of threads here:

http://www.videokarma.org/showthread.php?t=247011&highlight=wideband&page=2
See post #19 where I gave a quick explanation the single ended delay line, which, IMO, is one of the cleverest inventions in analog video IC design I have ever seen.

http://www.videokarma.org/showthread.php?p=2434742&highlight=wideband#post2434742
See post #132, where I talked about my analysis of a sample RCA set with the wideband circuit while I was working at Zenith. Basically, it looked like the IF couldn't support the increased bandwidth without quadrature distortion, and the high-frequency I gain seemed to be turned down to prevent visible edge effects.

Hi Members...........I have returned back to my 21TC55 "lab test bed" after about six months of doing other techi stuff. When I turned it on
about two weeks ago it came right up but was totally out focus due to CRT blooming. I checked all the standard operational readings I use
for setup: Room Temp=60deg, AC input=115vac, B++=424V, FBI=200ma, boost=770V, ultor=30KV, focus=5.4kv, all normal for this
"experimental" setup. After one hour running, RT was 70deg, AC=115, B++=415V, FBI=199ma, boost=800V, ultor=32KV, focus=5.8KV.
No CRT blooming, fine picture. I measured the CRT heater voltage direct at socket with a true RMS Fluke DMM. It read 6.16vac. I installed
an old CRT booster that raised the heater to 7.64vac. The neck was much brighter of course, so I left the TV on for only a couple of hours.
The set was running at 2% under spec heater all these years and now it was running 20% over spec for two hours. I turned the set off.

Nest morning at 7am, RT was 54. I powered up with booster off, the 21CT55 came up with no bloom in perfect focus! Readings were AC, 115V, B++, 420V, FBI, 200ma, boost, 860v, ultor, 33KV, focus, 5.6KV, heater read 6.01vac. After about 4 hours running with fans off, RT, 74deg, Ac, 115vac, B++, 422, FBI, 190ma, boost, 780v, ultor adjusted to 30KV, focus, 5.7KV, heater, 5.93vac. No blooming, good picture so I measured the FBX temp with digital thermo meter applied direct to primary and EHV secondary. Max temp was 112deg, barely warm!

Pleasant surprise, the CRT shutoff uniform glow problem was greatly reduced, almost unnoticeable! Could it be the 21FBP22 running low heater all these years allowed contamination to build-up on the cathodes causing loss of emission and/or causing grid emission that produced the glow? In-the-day the CRT boosters were quite poplar for restoring brightness and were left in place running at close to 8vac which shortened CRT life considerably. I always took them off after a few days/weeks, often with no noticeable decrease in brightness or increase in blooming.

I still have this problem with the hybrid combination of original CTC2B horizontal oscillator and 6CB5 HOT driving a CTC16 flyback xformer and
associated components, driving the original CTC2B yoke. This mismatch works fine but since it has no width control and only limited centering control, the screen is over scanned about 2 inches and is off center about 1 inch. This is unnoticeable except on test patterns.The BIG problem is the very noticeable horizontal video "fold-over" on the left screen presumably due to the horizontal sweep flyback starting up before the previous field's
video is blanked? The magnetic horizontal deflection of color CRTs is probably the most heavily engineered, most critical component matching
requirement, highest efficiency consumer electronic system of the 1950s. It obviously does not permit the "hacker" approach to customizing I usually pursue. I've tried all the usual modifications using all combinations of resistance, capacitance and inductance to reduce the horizontal width
and enable horizontal centering with no success and almost tragic results. Soooo, I am now designing a video blanking circuit that cuts off the foldover contaminated video for the first portion of every video line. It starts immediately after the chroma burst and extends three microseconds which
completely removes all visible traces of video foldover from the screen. Once I get this circuitry installed into the CTC2B under-chassis I will do a painful optimal convergence and be ready to take a batch of screen shots with Judy's new Sony DSC-HX9V 16.2 mega pixel pocket camera.

The CTC2B with "gray screen" 21FBP22A CRT combination has an extreme dynamic range that displays to the human eye details into deep shadows that our other cameras failed to capture. Hopefully, the Sony camera has a greater low-light dynamic range?

The video gate module is now installed, works perfectly! I'll probably do a convergence tomorrow and if I survive I'll take some screen shots with the Sony..........Tom

Sounds like your CRT is going soft. A strong tube will not lose emission, even at 5.5 volts on the heaters.

I have seen this phenomenon on black and white and color tubes over the years. I suspect the tube is going a bit gassy and the cathodes do contaminate. The higher temperature cleans off the cathodes. That's my guess.

I suspect that over time the emission will diminish somewhat and you will have to burn the cathodes again.

Thanks for the update! Always looking for your posts on the test bed, as they really help others, even those who don't have a CTC-2B.
Going to start on two 7's this winter. Should be fun!:yes:

Thanks for your renewed interest in the "21CT55 Test-Bed". Today I turned it on and still got immediate full brightness with perfect focus and boostless CRT heaters at 5.94vac! I agree with Pentode that running the 21FBP22A at 7.64VAC for 2 hours seems to have accomplish a very gentle CRT rejuvenation. It probably cleaned the cathodes and possibly burned-off any control grid contamination. The cut-off glow is virtually gone!


Hey, if all I have to do is occasionally run the Big Sucker at 7-8vac for a couple of hours to restore performance, I think I'll keep it....Tom

Tom, IMO you are asking for another flyback failure running at 30-32KV. That flyback was not designed to run with that much HV. The 21FBP22 has a maximum limit of 27.5KV anode voltage.

He won't listen, I've already told him. Nevermind the fact that if the max ratings are exceeded, x-ray production goes beyond limits deemed acceptable.

John.....I appreciate your concern for my old 21FBP22A and my new Flyback that's used on at least CT16 thru CT20s. I consider my 21CT55 a bench-top test-bed rather than a candidate for the usual chassis restoration including the mandatory complete recap. My stated long term goal for this test-bed is to demonstrate thru screen-shots the picture quality potential of the wide bandwidth I Q demodulation and low-level matrix processes of the CTC2B chassis teamed with what I consider the best roundy CRT, the grey screen 21FBP22A rare earth. Since I don't consider my 21CT55 a sacred icon of early color TV technology, I am at liberty to take reasonable design risks in the crucial horizontal deflection and EHV ultor system. The original 58 year old FBX that failed developed a short in its primary as the result of rotted insulation due to simple old age rather than over voltage in its secondary.

That said, the replacement FBX's secondary is not the universal winding of the original but a uniform wound solenoid stack of at least 30 to 50 layers! It was completely encapsulated in a multi layered rubbery boot to keep moisture out.

RCA used this FBX in the last 6 or 7 CTCs of the roundy series. I've been using it in my 21CT55 since December 2010 at EHV of 25kv to 35kv with HOT currents of 195ma to 205ma. In all cases it's coil temp has never exceeded 120degF with no fan at room temps of up to 70degF and 112degF at room temps of 95degF with a small fan directed at the FBX. The 21FBP22A is rated at 27.5kv max.This was probably dictated by barely detectable X-ray emissions rather then electrical breakdown within the CRT. It too was subjected to the same sustained 35kv as the FBX secondary. Standard high production engineering practices at RCA would not permit fielding of a consumer product without a proven safety factor of at least 20% to 30%. So 27.5KV times 120% says this FBX CRT combo should run all day with an ultor of 33kv! My performance ultor is now 30kv. The 21CT55 produces this ultor voltage with only 200ma current at the B++ fuze location which is the same current as the HOT cathode current.

Since I feel obligated to push the envelope of the 21CT55 I employ continuous monitoring of all critical parameters during all running of the TV. These include mains input held at 115vac, measure of B++ voltage, HOT current, Boost voltage, Ultor voltage, focus voltage and even CRT heater voltage at the tube socket.

Most importantly, I never allow the TV to run with screen display when I leave the room. I have a switch on the chassis that disconnects the B++ into the horizontal section but leaves all other sections active with tubes on. I hope this drone leaves you and miniman somewhat more comfortable that I'm not unnecessarily destroying a 21CT55 I've had since 1964.

John,


Told ya so. :smoke:

Ah well...concern expressed, now not my problem. :-)

Dosimeter, anyone?

Hello Mr. Tomcomm,

Have you ever done any bench testing / experimenting with broadcast monitors such as Conrac or Sony CVM PVM series? Or are you only interested in the ctc2b/grey screen combination?

After three garbled one-liner negative responses to my lengthy rationalization of my CTC2B test-bed effort, one reasonable response was finally posted. Yes, RobtWB I have a Sony PVM-1344Q composite / component pro monitor. I use it as a lab standard when comparing the picture quality of the CTC2B with a perfect comb-filtered pro monitor standard. I will use it after I converge the CTC2B and take screen shots with the new Sony DSR-HX9V camera, soon. Perhaps the three first-responders would care to elaborate on their vehement, specific objections with my present CTC2B operation at 30KV ultor, which is only 9% over max and runs only 200ma HOT current?

Perhaps the three first-responders would care to elaborate on their vehement, specific objections with my present CTC2B operation at 30KV ultor, which is only 9% over max and runs only 200ma HOT current?


I for one already have, in your meltdown thread:

http://videokarma.org/showthread.php?t=249148&highlight=tomcomm

John Folsom has much more knowledge on these old sets than I ever will, if you won't listen to him why would you listen to me (again)? Let me reiterate that your experiements are worthy, I simply fail to see what you hope to obatin by operating these parts beyond their rated limits. My 21-CT-55 makes a fine picture indeed when operated at normal current and voltages (when the tuner isn't acting up), just ask anyone who's see it. My intuition tells me that you're more likely to find improvements in picture quality by providing a better signal to the CRT, like gutting the decoder entirely and going with something more modern. I don't think anything you're doing with respect to HV production has anything to do with your results, or any improvement in picture quality. Just my opinion.

I will simply add that operating the flyback at elevated voltage levels increases the chances of flyback failure. I have no science to quantify the risk, so if you are happy so be it. I expect there is a very modest radiation risk, you should at least keep the HV cover on (shielding the 6BK4). There is probably some potential risk for a CRT internal arc over, but once again, if you are happy with the risk, so am I. As I said, I just wanted to express my concerns, and after that, it is not my problem to worry about. Have fun!

Hello- I've watched this thread with great enjoyment and also admiration for your skilled work... I have no idea how much of a risk you run with a nominal hv of 30kv but I doubt it's emitting significant x-radiation. It goes without saying that the shields around the rectifier should remain in place at all times. Remember the 70s sets like Zenith that would knock the necks off the tube bell, they were supposedly spiking to about 40kV for that to happen. And of course G-E in the later 60s.
If all seems well, it probably is. Smart to check HO current to make sure.

Nice piece of TV history!:yes:

Much of your video drive experiments I find facinating, and would like to learn more about.

However like Nick and John I would not try to elevate the HV. These sets are plenty bright at 25KV, and any gain from running it high does not sound remotely worth the risk to me.
I reciently revived a CTC4 and on the first run in which I had good video I let it run about an hour, and even though no damage was done, by not preforming the sam's horizontal adjustments, I was kicking my self when after powering down I found the flyback to be warm. If I can't get a fly to run cool and or within factory specs it prevents me from being able to fully enjoy a set as I become paranoid over the possibility that I may be ruining an IMPORTANT piece of a prized possession which I can't readily get a replacement for.

A flyback is like a good car if you treat it gently, and give it the proper care it will out last you, but if you ride it hard and push the limits enough it will eventually fail catistrophicaly.

I guess you are not subjecting it to the worst conditions a fly has endured, but you are still rideing it kinda hard. What you do with it is your business, but if you don't want to be looking for another flyback please make sure to carefully monitor it, and be prepared to pull the plug at the first warning sign of failure.

Good luck! Here is hoping you don't toast another rare fly.

Seems I need to reiterate a few items that continue to provoke Member comment.
#1 Why do I insist on running the new FBX and the old CRT at “extreme” ultor voltages? Well RCA and GE 21FBP22 spec sheets specify max operation at 27.5KV. This level is undoubtedly driven by fussy Government X-ray mandate. The specs also notes: “Brilliance and definition decrease with decreasing ultor voltage.” Enough said?
Since brilliance and definition increase is what I’m after why shouldn’t I run at 30Kv (109%max) on a new “modern” FBX that requires only 200ma HOT current, at a winding temp of only 112degF! This new FBX is like a brick compared to the fragile original CTC2B FBX that ran 28KV at 264ma HOT.
#2 miniman has stated that I could ”find improvements in picture quality by providing a better signal to the CRT, like gutting the decoder entirely and going with something more modern”. Apparently he has missed the point of my entire effort to demonstrate the superior picture quality of the original full BW I/Q demodulation and low level matrixing of the CTC2B chassis. Was he serious or just being facetious ?
#3 My CTC2B is not in a cabinet in the living room or bedroom used as a daily watcher. It will always reside in the garage lab and most often not operating when I’m not there. If I’m “experimenting” with it, it will be fully instrumented as I described. Besides I have two spare, exactly the same FBXs in new RCA OEM boxes in a safe place in case of a highly unlikely FBX meltdown.
#4 My grey screen 21FBP22 may not be a 21FBP22 after all. Has any member ever seen a light grey screened FB, most are olive green? Bought mine from a rebuilder for $45 who said it was an FB but it doesn’t have any markings on neck or bulb. Doesn’t all CRT rebuilds have an obvious glass weld on its neck, mine doesn’t? On close screen inspection with mag-glass there are 3dot clusters of identical light grey with single darker grey or black dots between the 3dot clusters. Could my CRT be a replacement 21GUP22 or a 21GVP22? Electronic M posted a full screen color bar off his Silvertone that looked identical to one pic I took off mine, it looked great! He stated someone at ETF said it was a 21GUP22. How about it Tom, does your 21GUP22 have a light grey non-energized screen? Please reply...Tom

Does you tube have a bonded safety glass?

John, not bonded. My CRT had a screen safety glass held in place with a foam rubber ring.

If it is not clear, then it is a grey filter glass, which may explain your phosphor color. I have a 21FBP22 which has had its safety glass removed, and the screen is a slightly greenish tint.

I don't know how to identify you CRT type by looking at the face, but someone else may.

FJP=bonded
FBP=non-bonded

Either one with the safety glass removed will look identical, the tint of the screen will let you know which phosphors are in it. Green=sulphide, paper white=rare earth. That's the way I understand it. The RCA sheet I am reading says the 21FBP22 is an all sulphide tube, but I had a rebuilt one that said right on the side of the box 'rare earth' with a grey screen... So perhaps the FBP's came in both flavors, or it could be that a rare earth tube that was bonded in effect becomes an FBP once the lens is removed.


#1 Why do I insist on running the new FBX and the old CRT at “extreme” ultor voltages? Well RCA and GE 21FBP22 spec sheets specify max operation at 27.5KV. This level is undoubtedly driven by fussy Government X-ray mandate. The specs also notes: “Brilliance and definition decrease with decreasing ultor voltage.” Enough said?
Since brilliance and definition increase is what I’m after why shouldn’t I run at 30Kv (109%max) on a new “modern” FBX that requires only 200ma HOT current, at a winding temp of only 112degF! This new FBX is like a brick compared to the fragile original CTC2B FBX that ran 28KV at 264ma HOT.

RE: x-rays

The spec sheet carries a specific warning for shielding, even when operated at it's max ultor voltage of 'only' 27.5kv. Going over that limit implies additional risk of increased production of x-rays, so you're taking your chances. The other very good reason not to push too much voltage is not to protect the chassis, but to protect the tube itself. When the HV is increased, so does risk of internal arc within the tube. If you don't much care about the chassis or tube (or your testicles), I don't suppose it matters. :D Also the 6BK4C shunt regulator sheet rates 'absolute max' plate voltage at 27kv, for the same reasons as the CRT.

RE: brilliance

This is what the spec sheet says:

"Brilliance and definition decrease with decreasing ultor voltage. In general, the ultor voltage should not be less than 20,000 volts."

(the part you left out is in bold, because context matters)

Since the tube is specified to be run between 20-27.5kv, I interpret this to mean that when run at voltages lower than 20kv brightness will decrease. RCA themselves only applied 19.5kv to the early picture tubes with the CTC-5 chassis, so there's some wiggle room on the low end when you are hoping to preserve some level of performance. Where your logic runs amok is assuming that it's all good to use the same wiggle room rule at the upper end, when the reality is that maximum ratings should never be exceeded for safety reasons. I am also a mechanic, I can tell you that the same logic will not fly in engines. "it's good at 10 lbs of boost, there is no problem running 15 lbs through it." I promise you this is not the case, many people have melted expensive parts with that kind of thinking. With high voltage and vintage electronics in close proximity to your body, the chances of walking away from a 'wreck' are not as good as with a car that has air bags. Hope my analogy makes sense, it's about safety more than anything else. I fear for your safety, guess that makes me the 'attack dog' as you put it in your other thread. So be it, at least I said something. I have washed my hands of this.

My goodness. The man has been experimenting with this set for almost fifty years. Experimenting. It hasn't burst into flames so far - do we really need all this bickering back and forth?

#4 My grey screen 21FBP22 may not be a 21FBP22 after all. Has any member ever seen a light grey screened FB, most are olive green? Bought mine from a rebuilder for $45 who said it was an FB but it doesn’t have any markings on neck or bulb. Doesn’t all CRT rebuilds have an obvious glass weld on its neck, mine doesn’t? On close screen inspection with mag-glass there are 3dot clusters of identical light grey with single darker grey or black dots between the 3dot clusters. Could my CRT be a replacement 21GUP22 or a 21GVP22? Electronic M posted a full screen color bar off his Silvertone that looked identical to one pic I took off mine, it looked great! He stated someone at ETF said it was a 21GUP22. How about it Tom, does your 21GUP22 have a light grey non-energized screen? Please reply...Tom

It is ironic that somebody would bring the set up only a few hours before it had a major breakdown.....
First off it's screen is not a light gray, but rather a dark gray that matches the mask. It almost looks like a modern dark face CRT with the safety glass on (it has been too long since I have removed the glass to remember the color, and I didn't snap a picture).
http://i1095.photobucket.com/albums/i469/ElectronicMemory/DSCN0433.jpg
It is the (I believe) factory original CRT and is a type 21GUP22.
http://i1095.photobucket.com/albums/i469/ElectronicMemory/DSCN0447.jpg
I believe that this is the color bar pic you mentioned.
http://i1095.photobucket.com/albums/i469/ElectronicMemory/DSCN0432.jpg
I believe that it may have been Mark who said to me at the 2010 ETF meet when I got it that he thought it may be a black matrix type. Which is quite possible. I did some cateracting this summer and was able to compare a genuine black matrix rectangular delta-gun CRT to a regular type of the same size, so if I take the tube out of the Silvertone during trouble shooting (I have to readjust the mountings anyway so why not take it a step farther) I'll get a shot of the phosphor and try to determine if it is a black matrix type.
My set is a clone of an RCA CTC-15 or CTC-16 and lacks the benifit of an IQ demod scheme. I suspect that the alignment is lousy on mine. The colorimetry heretofore has been outstanding (ignoring that the screen adjustment balance tends to vary over the course of warmup and extended viewing), but the picture detail both color and mono can't hold a candle to my 71' Zenith Chromacolor hybrid (when the Zenith's focus and color circuits feel like warming up and doing their jobs that is).

Tom, sorry my innocent inquire broke your Silvertone! I must be more careful in my future posts. Thanks again for your interest in my inquiry and your great screen shot postings. Anyway, I now believe my 21FBP22 can't possibly be a 21GUP22 since I bought it in '64 and its " nonactive screen color" is definitely "paper-white" indicating rare-earth as miniman posted. Its most likely a "rare-earth" 21FBP22A as I always suspected and stated in my posts. So is that good or bad from a Picture Quality standpoint? Are the saturated reds of the rare-earth 21FBP22s more like the 15GP22s and 21AXP22s then the more numerous olive-green screen sulfide 21FBP22s? The last time I saw a 21AXP22 was my Dad's CTC4 when I replaced it with my present 21FBP22A 48 years ago. In fact, I haven't seen another roundy of any kind besides mine ever since. All I know is my 21FBP22A reds are obviously more "RED" then my 13in Sony Pro monitor which has SMPTE-C phosphor and my 27in Sony comb-filtered monitor. Both Sonys are orangeish-red in comparison. I was told the SMPTE-C reds make the reproduction of flesh-tones more natural? I would like to see a rare-earth, paper-white screen 21FBP22 included in any serious comparisons with other 21in roundy including Tom's 21GUP22 and the original 15GP22s.

Its most likely a "rare-earth" 21FBP22A as I always suspected and stated in my posts. So is that good or bad from a Picture Quality standpoint? Are the saturated reds of the rare-earth 21FBP22s more like the 15GP22s and 21AXP22s then the more numerous olive-green screen sulfide 21FBP22s? All I know is my 21FBP22A reds are obviously more "RED" then my 13in Sony Pro monitor which has SMPTE-C phosphor and my 27in Sony comb-filtered monitor. Both Sonys are orangeish-red in comparison. I was told the SMPTE-C reds make the reproduction of flesh-tones more natural?

All rare-earth reds are less orange than the zinc cadmium/sulfide red, especially as the sulfide red shifts even more orange at high beam current. Rare earth reds can vary somewhat among them, but not as orange as the sulfide. The big difference in all tubes after the 21AXP22 is the sulfide green, which is much more yellow than P1; and to some extent the sulfide blue, which is a deeper blue (less cyan) than the 15GP22. Other differences you see in your Sony and other sets can be due to the color matrixing, which was adjusted to get reasonably natural flesh tones. Depending on how much matrix redesign was done, you could also get a sort of auto tint action that reduced the variation in flesh tones to some degree.

You may recall that in some cases when an earlier CRT was replaced with one with more efficient red, there was a change made to the cathode drive to reduce the red Y drive. But the R-Y gain was not reduced. The reason is that the new tube also had a yellower sulfide green. This was like adding some red into every green color, so the high R-Y amplitude tended to compensate by turning off red harder on greenish colors. This corrected the range of hues from red to orange to yellow to green, but also lit up reds too brightly. This compromise was subsequently built into all consumer NTSC sets to some degree, and a SMPTE-agreed amount was built into professional monitors, but with a matrix on/off switch.

Some of the impression of "redder" reds with the older tube comes from the contrast with the P1 green but also is due to the not-overly bright reds (even if they are slightly orange) and/or due to not having a matrix that was fudged to reduce flesh tone variations.

By the way, if you want an example of "how red" NTSC reds should be, note that red traffic signals are outside the NTSC gamut, but incandescent car taillights are not. Most rare-earth tubes are actually close to NTSC red - it's the greens that are way off.

I believe that my setting the Silvertone on the carpet (thus causing the bottom vents to be blocked) because I needed to remove the set it was sitting on to make room for the CTC4 was the reason it quit. I'll have to pull the back to find the scientiffic cause of the failure.

I can't compare the 21GUP side by side to the white face 21FBP until I get the CTC4 (which is using a white face 21FBP) working right, but I can give a qualitative, across-the-Midwest comparison of the 15GP (in the CT-100 at the ETF) and the 21GUP in my set.....The 15GP has deeper greens and better saturated colors overall than any other set I've seen in operation (except maybe Nicks 21-CT-55), but my 21GUP comes closer than any other CRT I own ( and have used in a properly adjusted set) to the stunning colorimetry of the 15GP.

Wayne. I understand the original RCA CTC2 chassis was a true I-Y/Q-Y axis chroma 90 degree quadrature demodulator system to precisely recover the two chroma components in quadrature sent by the transmitter.. However the CTC2B chassis is a R-Y/Q-Y chroma non-90 degree axis quadrature demodulator system. Seems "The General" ordered RCA engineers to adopt this "buggered" quadrature demodulation system on the CTC2B to avoid paying a license fee to I believe Philco. The R-Y axis is 90 degrees from the reference burst and 33 degrees from the proper I-Y axis, any inherent R-Y demodulator component errors could be "mostly" removed by resistor changes in the chassis's low level matrix system. My Sept 11,2007 21CT55 reactivation project notebook indicates I considered the modification of the CTC2B's irrational R-Y/Q-Y matrix to the CTC2's proper I-Y/Q-Y configuration a no-brainer, accomplished with the addition of 2 resistors as shown in Oct 13,2007. This was the first of many "experimental" modifications I would make to this chassis. I had already exchanged the original 21AXP22 for the much brighter 21FBP22A rare earth in 1965 and made no suggested chassis changes to compensate for differences in CRT brightness. The picture quality of the present 21CT55 is quite acceptable but could possibly be better with a rigorous colometry alignment in the near future.....Tom

...I can't compare the 21GUP side by side to the white face 21FBP until I get the CTC4 (which is using a white face 21FBP) working right...

Actually, it should be possible to determine with the sets not operating. With a strong magnifier, you should be able to see if the phosphor dots are separated by black matrix material.

That quote of mine had NOTHING to do with checking for black matrix. I was talking about operational colorimetry.

It is difficult to get a good look at the phosphor dots of the 21GUP with the safety glass on...So I was planning to pull the tube and remove the safety glass and look at it up close with it not running (my eyes are young, and considering I've seen a delta gun black matrix CRT up close before I should be able to tell if it is one by naked eye).

Tom C., sorry I misread that you intended not to look for the black matrix in the non-operating condition.

If a tube is black-matrix, it definitely will not have NTSC green. The chroma electrical matrix (or equivalently, the demodulator gains and angles) can provide some correction and can give very pleasing color, but cannot make the green phosphor less yellow or improve the cyan saturation to the same level as a 15GP22. Also, the corrections that fix the hue range between red and green always result in making the reds brighter and the cyans darker than a tube with NTSC phosphors, as a result of the tube gamma characteristic.

This is a 900X600 JPG composite containing 54 100x60 JPG 21CT55 screen-shots. No particular significance implied, since each was originally shot at 1024X768 JPG. Picture Quality screen capture has always been the main object of this RCA CTC2B monitor-only project. More full size screen shots will follow.

http://i677.photobucket.com/albums/vv134/tomcomm/PV%20Before%20Trim/CopyofFlicker2010.jpg

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.

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.

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

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.

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?

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-100TelevisionDesign.htm#Whats_Your_Color_IQ

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?

Also does digital tv still process color the same way?

Not even close...

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.

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.

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

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...

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.

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.

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


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

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?


The luminance of bright saturated reds is nominally 30% of white, but due to CRT gamma and gamma correction, while the luma SIGNAL is 30% of max, the luminance of the resulting gray is about 0.3 squared or 0.09. The luminance is restored to 0.30 when the chroma signal is turned on and sets the red to 100% (green and blue reduced to zero %). This means that the chroma signal provides 2/3 of the red contrast. When the chroma bandwidth is reduced, it means that details in a red rose, for example, have only 1/3 of the original contrast. Hence, such red objects appear to have reduced sharpness. [Edit - the wideband I channel restores most of this detail contrast.]

Saturated blue objects (with details varying from full blue to black) will have the same type of loss of contrast, with the original 11% of the full black-to-white range changing to only 1%. This may be less or more noticeable than the red problem depending on the over-all content of the scene. If the scene is entirely blue, it will be much more noticeable than if the scene contains full black to white contrast and some blue objects.

If the blue is deep violet-blue or purple, it will be carried in the narrow Q channel, so will not be improved by the wider I bandwidth.

It really doesn't matter, in the long run. The MOST IMPORTANT thing is that ANOTHER veteran has been saved, & looks GREAT !

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

This statement suggests the CRT is dot-limited in its ability to display the picture quality improvement of the CTC2B’s wide-band IQ demodulation chassis. The 21FBP22 spec places the distance of adjacent RGB dot clusters at .029 inches. Since the horizontal screen width is 19.25 inches, a maximum TV line without overscan is composed of 664 clusters which will produce 332 line-pairs of resolution. At the accepted TV value of 80 line-pairs per mhz of video bandwidth, the 21FBP22 will support up to 4.15 mhz video bandwidth! This is sufficient for 4.10mhz video of high quality B&W TV and way sufficient for the limited 3.2mhz Color TV luminance video. This CRT easily supports the CTC2B I chroma channel’s 1.3mhz video bandwidth to produce 104 line-pairs of I chroma resolution. This resolution is far greater then the 40 line-pair resolution produced by the .5mhz R-Y, B-Y chroma bandwidths of the CTC4 and later RCA roundys.

Obviously, the quanity of phospher dots can’t possibly limit the ability of a knowable observer viewing a 20in CRT at a distance of less than 40in to determine relative picture quality. The CTC2B’s wide bandwidth I chroma resolution is 260% higher then the CTC4’s and later equi-chroma bw CTV’s resolution. Of course, this difference is most apparent on chroma resolution charts but will certainly be noticeable in any high quality natural scene and will be manifested by obvious reduction in picture quality.

Tomcomm, you are correct that the triad spacing does not limit the I channel resolution, but your arithmetic and nomenclature are confused.

TV resolution is not specified in line pairs, but in lines (film resolution is specified in line pairs). Furthermore, TV resolution is specified in TV lines per picture height, that is, a distance of 3/4 picture width. So, the correct number is (as you said) approx 80 lines (not pairs) per picture height per MHz, or 80x4/3=107 lines per picture width per MHz. Another way to calculate is the number of half cycles of 4.2 MHz per active scan line (~55 microseconds), or 462 lines of luma resolution. (This is a bit of an overestimate; a good rule of thumb is 440 lines per width or 330 per height.) The spacing of 664 triads per width means that the ratio of spacing to maximum luma frequency (if those sets had comb filters) would be 664/440 = 1.5. Thus, there is little chance of moire' caused by fine detail. In the actual sets with limited luma bandwidth, the ratio is a very generous 2:1. The I bandwidth is 1/2 the limited luma bandwidth, so it clearly can be carried by the screen structure without limitation.

The more important ratio in the 21 inch and later color tubes is the vertical spacing of triads compared to the line spacing, because there is always the possibility of a moire' pattern caused by the scan lines interacting with the triads.

Later smaller tubes, particularly the Portacolors, had insufficient numbers of triads to support full resolution.

I have an RE21FBP22A that was found in a relative's garage. He used to be a Sears repairman back in the 60s & 70s. Still in the tattered box and unbroken.

Where are you located? I might be interested. Welcome to the forum.

Long Island, Ny

Oh, that's a bit far as I'm in the Kenosha, WI area. I've had bad luck with shipping things like that. Thanks for letting me know.

IF you build a good double wall cardboard box with proper baffles and supports, and ship using Greyhound, you can keep the costs reasonable. I have shipped numerous 15GP22s and 21AXP22s ans 21CYP22s using Greyhound, with NO PROBLEMS!

I have gotten my fair share of Roundie CRT, recording consoles, tape machines, etc safely and in one piece by Greyhound. The best way to haul such gear. :tresbon: