Restoring a RCA 21CT55
 

https://visions4netjournal.files.wor...2/img_2449.jpg

Well over a year ago, we purchased a 21CT55 from the Early Television Foundation. It has been a long haul, 470 days and the restoration is completed.

Steve McVoy, Dave May, Bob Galanter, Kevin and Mike Doyle (edit: I left out Walter) all members of this forum helped with the restoration. I want to thank them very much. It could not be done without your help.

You can see screenshots along with a chronological accounting of the restoration from day one at this link:

https://visions4netjournal.com/vinta...p-carousel-967

Moderators, apologies for the large screenshot. Can you reduce the size?

Very good job. Looked at the pictures on the visions link, and the color is great. I have a 21CT55 also that I restored, and is working as well.

Thanks Walter. I forgot to acknowledge you. You also helped me isolate the power switch problem.

I followed your 21CT55 restoration thread. Was inspired.

Wow! Wonderful restoration and documentation of the restoration of one of the very most desirable of the milestone color sets!

jr

Out of curiosity what was the problem with the power switch. If I remember right we chatted online and you said it was dead completely. I suggested the power switch and some of the places you could check it out without pulling the chassis. Was it the switch itself as I suspected? If so did you find a replacement switch with volume control? Also is your cabinet the original finish? Looks really good in your first photo. Mine was really sun faded, (especially the top and one side), so I finished it with Minwax stain. I really should have had the cabinet professionally refinished, but was afraid to remove the 21AXP22 as I didn't want it to go to air. Sanding and stripping the cabinet (with the CRT in place) also felt very risky because of the vibration if I had left the CRT in the cabinet. Maybe someday I'l be brave enough to remove the CRT and take the cabinet to a pro refinisher.

Welcome to the 21CT55 club. I would like to see some full screen size, screen capture shots. I assume your included screen shots were thru the full RF/IF systems, right? It would be interesting if you could compare them with your computer monitor screen shots. Seems you have some color aliasing contamination in the small detail. Looking forward to your further screen shots.

Walter,

You were right, it was the power switch that failed. We found out the switch was a replacement sometime in the set's history. It was incapable of handeliing the high current on power up. The switch had a 3 amp rating but the transformer was drawing higher current. Mike suggested we install a relay to draw the current and lessen the load on the switch which was replaced to the correct value. This was done to preserve the switch for long life. I'm so glad we did because the room light dims briefly on power up. The brightness control and volume control which were integrated with the power switch were retained.

The cabinet was in good shape. There was one scratch on the side which was touched up without refinishing the entire cabinet. The safety glass was removed and the CRT and glass were cleaned. I share your concern and the CRT was never removed during the restoration.

I need to refinish the brass around the safety glass. I don't want to remove the glass if possible. Do you know of a good product I can use to remove the patina? I tried Brasso and it had no effect.

Tom,

In the link I provided, (within the image carasel) you can click on a tab to see the full resolution shots. I used a non-pro camera, an iPhone 6 Plus to capture the shots. The signal was OTA converted to analogue with a converter box. I'm still planning to adjust a bit more and create a video. I followed your treads on the 21CT55 and that CRT produces about the best color CRT screenshots I've seen from an old "roundie". The original CRT (21CT55) was replaced with a newer tube, right?

Thank you very much JR. :-)

That is odd...The same trim was used on the CTC-4, and I polished that trim on my CTC-4 with brasso. Did you forget to shake the bottle before using or forget to scrub?...I had to scrub mine vigorously with a discarded toothbrush to polish the tarnish off.

I tried with a soft cloth. I good try your meathod or maybe a Dremel tool with fine sandpaper, then seal with varnish?

The only way to get good results refinishing the brass is to remove the trim and work at it with successively finer grades of steel wool or scotch bright. The brass has a lacquer coating, that was sprayed on at the factory. Brasso will not do anything unless the brass is bare naked. Then Brasso can remove the tarnish. If you try to remove the lacquer coating using Brasso and a soft cloth, you will be expending many needless hours of labor

Removing the brass trim is easy. Behind the crt bezel you will find tensioning clips that hold the trim in place. Remove all the clips that hold the trim tabs in place. Then you can push the trim tabs forward, through the crt bezel and the trim frame can be easily removed.

If you try and clean the trim with Brasso with the trim in place, you will end up with Brasso in all the crevasses, and then there is still the problem of having to apply a new coat of clear lacquer to prevent future tarnish. No, varnish is not the correct product to use.

Click on the "Brass Refinishing" link under "MY Methods" section at my web site or click below

http://antiquetvguy.com/WebPages/MyM...finishing.html

Bob,
I found out quickly about the Brasso getting in crevices as well as a soft cloth not working. Thank you for the suggestions.

Great Job! Went to your website and saw the pictures....I just started working on my 21CT55 again....you cant beat seeing Spock on a 21AX!

etype2,
You might consider Bob's method of removing the old lacquer, but instead of using Brasso to polish the brass, use MAAS polish. I do brass instrument repair and restoration (I specialize in higher end pre-war Conns) and MAAS is the polish I always use before either silver plating or hitting the horn with new nitrocellulose lacquer.

Kirk: Thank you.

Ben: Thanks for the tip. Never heard of it, checked their website, looks like an excellent product. I will give it a try.

Brasso tends to leave a mottled appearance to the brass, only visible once the lacquer is on it. If you use Brasso before silver plating, sometimes the plating process will fail; you'll get a blotchy uneven finish no matter how you try to clean the Brasso residue. I've never had either problem with the MAAS. You're mileage may vary of course.

Would that be good for bronze as well? The handle on my Heathkit GR-370 had the most crap I've ever seen on decorative hardware, bar none. It's mostly gone now, but the hardware is still badly tarnished.

Yes. I've used MAAS on bronze with great success, and even on pure copper (a Conn 12B with the "Coprion" type bell). It works great on silver too, but electrolytic cleaning is always a better first line of attack with silver. At least with electrolytic cleaning you aren't removing any of the underlying plating.

Here is one more screenshot from my restored RCA 21CT55, captured from last nights tribute program to Mary Tyler Moore who passed away on January 25, 2017. Her show was a favorite of mine which ran from 1970 to 1977.

https://visions4netjournal.files.wor...2/img_5495.jpg

beautiful image and such a lovely smile... vale MTM ....

couldnt have found a better face to look at.beautiful lady and i very nice image on that set.

Thanks, Mary Tyler Moore will be missed.

Tomcomm: you asked for larger screenshots and a comparison to a computer screenshot. I'm not currently using a computer, just an iPad Air first generation. I have a 2012 Sharp Quatron 70 inch LCD TV/Monitor with full array LED backlighting. One notable feature is that it has 25% more pixels because of the yellow pixel. We had the set calibrated to ISF (Image Science Foundation) Rec. 709 standard three months after purchase in March, 2012. You can see the calibration charts on the "4K" page of my website. I estimate the set has over 29K hours on it. The first photo was captured with an iPhone 6 Plus of the Miss Universe contestant representing France and won the competition on this Sharp monitor. Fox broadcasts 720P not 1080i

1. https://visions4netjournal.files.wor...2/img_2822.jpg

2. The second photo is the same frame captured with the same phone off my RCA 21CT55. This photo was cropped to remove excess boarders.

https://visions4netjournal.files.wor...2/img_2799.jpg

3. The third photo is the same image as photo 2, but captured with the iPhone 6 Plus off the Sharp monitor by Apple mirroring.

https://visions4netjournal.files.wor...2/img_2825.jpg

4. The fourth photo is the same image as numbers 2 and 3 captured as a screenshot from my iPad Air formatted to it's 9.7 inch Retina display. When the iPad Air first came out, Display Mate website ran a test and declared it "the most accurate mobile display" at that time.

https://visions4netjournal.files.wor...2/img_2823.png

I don't know how "scientific this test is, but one thing for sure is you can see how much of the image is lost on a roundie CRT. I'm still not satisfied with the color on my 21CT55 and further "tweaking" is required.

It appears that the mirrored image lost image detail, etc. but I can tell you the Sharp monitor is very accurate. (See the calibration charts on my "4K" page.) https://visions4netjournal.com/4k/

Continuing .....

I'm not sure if it's an artifact of the camera, my vision, or both, but I see very little color in the lips on Ms. France.
I also don't see much green in the previous screenshots, but that could be an artifact between the camera, my display, and my eyes.

Ben,

Yes, that bothers me. On all the screenshots so far, women's lipstick just will not display well. The red is there though. You see it in her hair. I have a screenshot of JoAnne Worley from the Laugh In show in 1969 and her bright red feather boa displays with good red, but it doesn't pop.

On the pattern generator, all three colors look good. More adjusrtment with the color gain controls? Mike said the all three guns tested strong, just not new.

Don't expect lipstick or other really bright red things to look right in
real scenes.

Several things to check:

1) is your modulator being overdriven? That will do it. Step 2) checks this.

2) check B&W step patterns on all three guns ... be sure the red
one is not seriously overdriven. This will also check 1). I suggest lots
(like 30) of steps.

3) check the fine tuning and IF response with a full-screen horizontal
chirp test (e.g. Digital Video Essentials), with the color control all the way down.
There should not be a dark area where the chirp goes into
the color region (starting at say 2.2 MHz) . If adjustment of fine tuning does not get
a sharp picture (i.e. down more more than 25% at 3 MHz) , good amount of color
(on a color picture), and lack of the dark area, you probably need a full RF-IF alignment.

4) check the setting of the R-Y drive pot by examining the
R-G-B CRT grid waveforms with a scope, at low contrast settings, using
normal color bars. The should show all the bars at only two levels.
Adjust the R-Y pot, color level, and hue until its as good as possible on all three.

5) check adjust contrast and brightness for proper bar appearance
being sure that the red gun is just barely clipping.

6) recheck the gray step pattern to be sure it is uniform color. If
not, readjust screen and video gains. Be sure to check the red screen pot ...
all the way CW may not be best, run through the whole range. Then recheck 5).

I just did this yesterday on my CT-100 and found 6 to be a problem.
The gamma is too high on these CRTs and you may be unable to get
good bright reds and good scene visibility in dark scenes at the same time.

4) can't be reliably done by eye ... you may be setting with too much red clip.
You need a scope.

Repeat until you understand what is going on.

Doug McDonald

Doug,

1. Not using a modulator, but I plan on purchasing a very good quality modulator, maybe even a pro model. I suspect that my $50. digital converter is degrading the image. I say this because when we were testing on Mike's setup with modulator and DVD the images looked cleaner. I see "video noise" for lack of understanding of what I'm seeing. Also there is a faint vertical band in the center of the screen only visable in dark scenes. The band was not present with the DVD/modulator.

3. We did do a full IF alignment. I think that is why the this 21CT55 displays very good detail. I have a copy of the Video Essentials disk.

I suspect the red gun is being driven to high.

In the end, based on what we saw with the modulator/DVD setup on the bench and what we see with the digital converter now, our next step will be to purchase a high quality modulator so I can view DVD's on this set and go from there. I'm very happy with the image detail though.

Thank you for the excellent testing recommendations. We will follow through.

The Blonder-Tongue BAVM single-channel models are just fine. Yes,
the -SAW ones are better than the -z ones but I can't tell the difference
on any of my TVs. They are very cheap on ebay .. you can buy two or three.

And ... compared to the "agile" ones they run cool as watermelons.
The agile ones run very hot.

My Miniature 3 inch TV
 

etype 2 I’m very much impressed with your Miniature TV write-up. I was
repairing TVs starting in the seventh grade and bought a 3 inch Pilot TV-37
in 1951 for use as a portable test set on service calls, which my Mom drove
me to. For a junior high school science fair in 1952 I cut the chassis width
almost in half and folded it over to make the “Worlds Smallest TV”, or so
I thought! I still have it in it's crude cabinet and it still works, maybe?

The cabinet modifications of my 21CT55 to make it fit into my new tiny lab
was no big challenge. I replaced the weak 21AXP22 with a 21FBP22A
and made it a composite baseband video only monitor only.

Doug: Sounds like you see no difference in video quality between the two modulators. Can the Saw models be adjusted for over modulation?

Tom: Got it, you went for the purest signal to the television.

I got started with crystal radios in 1956, 9 years old, then with some help from my genius neighbor 3 years older then myself and already had a radio operators license, we got an old junker vertical console working. It was dumped in the back of a neighborhood TV repair shop. I asked if I could have it and he said it was junk but go ahead and take it. He helped me lift into my coaster wagon.

About the micros, thanks. A lot of them were bought new back in the day. I envite you to send me your favorite television's/projects. I will post photos and your information on my "Viewers Television's" page. The envitation is open to all who reads this.

The 21CT55 in action in this video.

https://m.youtube.com/watch?feature=...&v=weuaTgZuIPQ

After adjusting the color controls on the RCA 21CT55 the past view days, I think we have better color images. I took a slew of screenshots and the full size images can be seen here: https://visions4netjournal.com/vinta...e_preview=true

https://visions4netjournal.files.wor...2/img_7768.jpg

https://visions4netjournal.files.wor...2/img_3090.jpg

https://visions4netjournal.files.wor...2/img_3089.jpg

https://visions4netjournal.files.wor...2/img_7771.jpg

https://visions4netjournal.files.wor...2/img_7766.jpg

https://visions4netjournal.files.wor...2/img_7767.jpg

Your screen shots look great! Too bad you included some screen shots of Trump. This is not a political forum.

Thank you for the compliment. Never intended the post to be political. If it makes any difference, we posted a screenshot of President Obama on the 21CT55 on my website. Equal time.:thmbsp: No affiliation either way.

equal time is right.i wasnt offended by a screen shot of our president.that set looks fantastic!i remember seeing these sets when they were on display back then.the colors were vibrant and alive!thrilling to see.beautiful set and thanks for posting thoise pictures

Many who had a hard time putting up with the last guy, can't help but smile and laugh at those that can't manage to put up with the current guy. :D Reversals can be refreshing, and enlightening!

I didn't vote for either of those idiots. Clinton and Trump are both terrible people; you have to be in order to get involved in politics. That said, he is our president and I don't see how posting a screenshot of the inaugural is political. We're going to be seeing too damn much of the man, better buckle up and get used to it now.
Also, from the interaction I've had with etype2, I doubt very much this was a political statement one way or another.

I apparently offended at least one member so I removed the photos in question. I really never thought of the photos as being political, but I can see how someone might think that. To me it was an historical moment and for my own use, I wanted to preserve that moment, live as it happened.

I would very much prefer comments on the screenshots as captured from a 62 year old color television.

The set appears to be working wonderfully, and your excellent photography skills have captured it in all it's splendor. :thmbsp:

The WORST political posts are the False Equivalence ones where everyone is viewed as the same. Never thought we'd have to bear such here.