Welcome, this page continues the chronology of our 1954/55 RCA 21CT55 restoration. You have just “powered up” (metaphorically) the 21CT55 and can view our slide show program in the viewer below. Remember, these old tube color sets took up to a minute for the high voltage to come up to illuminate the screen. Should you not see images in the viewer, just refresh to “power” the set up. 😀
RCA 21CT55 COLOR TELEVISION VIEWER
Read about the restoration completion below, or go back to the first page to see the start of our project.
UPDATE, DAY 359, September 26, 2016.
Mike stopped by to pick up the 21CT55. We are going to address the remaining issues talked about on the previous page. We wrestled the 198 pound set out the house with a furniture dolly into his vehicle. We layed the set on its side because it would not fit vertically even with the legs removed. The below photo shows the set wrapped in furniture moving blankets and cushions. We also strapped the set down to prevent movement. The 2 1/2 hour drive to Mike’s home should be much smoother then the truck delivery.
UPDATE, DAY 363, September 30, 2016.
From Mike: I have begun the teardown. Please find attachments. I have removed the convergence yoke, purity ring, blue lateral magnet and “remnants” of the deflection yoke cover. The cover for the yoke will be replaced with some later model of which I am not sure yet. Some good news is that the convergence yoke “electrically” checks out fine Ohmically with a meter. That is a good thing. There is a picture of the crt socket which shows need for replacement. In particular, the wire going in to it for the focus voltage is suffering from insulation breakdown. I have that one covered! I did a check on the CRT with my B+K 467 and it checks out OK but not like a new tube. Not much of a surprise there. More on that later after I do some work on the set. I should be “jigging” this up within the next week or so and then I will know more about the power problem. I do not expect that to be any negative surprise but time will tell.
UPDATE, DAY 365, October 2, 2016.
Mike continues: OK, I have successfully mounted a good working RE21FBP22 to the workbench so I am ready to “jig” the chassis. I have removed the deflection yoke and cleaned up the plastic debris from the plastic yoke cover. I scraped the old tape (or whatever it was) from the yoke housing and did a test fit for a cover from a later model and it FITS!. I will have to do a little “body and fender” work to make the magnetic shield go back in to place but it is very doable. I will be doing some cleaning where the yoke was riding on the neck of the crt for 60 + years. I may even be removing the crt before all is over but time will tell on that. I will be jigging this chassis within the next few days and my first priority will be to learn whatever the power problem is. Please find attachments.
DAY 368, OCTOBER 5, 2016.
From Mike: Well, it’s on the bench but not jigged yet. Getting close on that one. I have however determined that the power problem is in fact the switch. YAY! The bad news is that it is a real bear to replace. I will send pictures later. Also, the switch shares functionality with the volume control and the brightness control. I found an unsoldered joint on the brightness control as if it had been disconnected for some kind of troubleshooting measurement and then forgotten. It raises the question to me, did the set show erratic brightness changes when you had it going? Just curious. The brightness, volume control and switch assembly will have to be removed completely in order to replace the switch section and it is a fair piece of surgery. I will have to be very careful not to damage the controls with excessive heat from the soldering iron. Another point of concern is the fine tuning knob is in dreadful condition. Most of the plastic that contacts the tuner part for fine tuning control is totally missing and that knob will have to be rebuilt somehow. I will put on my special “creative” hat for that one. Not sure yet how I will fix that. The only thing left for me to be able to “jig” it is to find a way to hook up the convergence chassis which requires a 9 pin type socket extension cable similar to a standard vacuum tube “octal” type but has nine pins instead of 8. The interesting part about that socket to me is that they only use 4 out of the 9 pins so why did they find the need to use a 9 pin socket. ???
Anyway, that is the progress for now. I will have more news in a couple of days if all goes well.
I removed the control assembly tonight. The pictures attached show the broken fine tuning knob, the removal of the switch/brightness/volume control assembly and the repaired unit with a new switch attached. I will install it within the next couple of days and then finish the jigging process. The convergence chassis with its 9 pin plug is really not a big deal since only 4 wires are used. I will be able to patch them in without a lot of trouble. So, next is the troubleshooting of the color problem, the tuner intermittent and convergence problem.
I will be thinking about how to fix the fine tuning knob. Also, there is an issue with the channel selector gear drive group. A plastic tab part of the drive system is missing/broken/gone and I should probably address that as well. I really want to make this set as robust as possible during this time in my shop.
Author’s thought. We may be able to replicate the fine tuning assembly with a 3-D printer. Mike’s son works for HP as a printer diagnostics engineer and is exploring the idea.
DAY 372, OCTOBER 9, 2016
From Mike: OK, now that we have talked about the knob, there is something that I noticed that we need to agree on for the fix. The switch that failed in your set is the second one (at least) that it has seen in its lifetime. This control assembly has been replaced and/or repaired by someone before me. The brightness control has been retro-fitted from some other control. This is a traditional practice when a manufactured assembly is no longer available. I have done this very thing myself during restoration procedures. I have several boxes full of old pots and controls that I pull from for such procedures. Long story short, is that this control has been replaced as an assembly, and also repaired before. The brightness pot unit is a 10K and the schematic calls for a 5 K. That explains why it had a 10K resistor across it in order to bring it in to proper range for good operation. OK, now let’s talk about the history of the switch. This set’s power transformer is very HUNGRY for current and the switch is rated at 5 amps. The problem I have is that the switches that are identical to this one that I have also seen a lot of, especially internal construction, are also rated at 3 amps. It makes me wonder if the 5 amp switches are any different than the ones labeled 3 amp. They appear to be identical. Furthermore, I conclude that these switches are OVERLOADED under normal operation even when rated at 5 amps!!
Now for my proposal.
I feel that for safety and for longivity of the switch, I install a 10 amp relay somewhere under the chassis which will serve as the “current” carrier and be controlled by the main switch at a much lower current level than the switch is trying to handle under the present conditions. This will actually take about a half an amp to actuate the relay by operation of the switch and let the relay contacts take the “hit” of the current. This is something that I would do if the set were mine, and I would do it without even thinking about why not. Let me know what you think, and I will proceed accordingly.
Author: We approved the modification. We feel this is an excellent precaution against future failure.
Mike: I finished the relay mod tonight and it works great! I will send a pix sometime later along with others. I have been looking over the chassis in general and I question (with all due respect) the peaking coils that were chosen to replace the failed ones. They appear to me as being low frequency type with heavy copper and I would expect them to be of much finer wire. I will be looking in to the specs on that from the RCA manuals and the Photofact parts list. I have also been investigating the issue with the tuner. I think I am going to have to “pull” it in order to polish the contacts and it is going to be a bit of a project. So far, nothing I can’t handle. I have not jigged the chassis yet but I am getting close. Lots of things getting in the way right now but I see a light at the end of the tunnel. I also noticed when I was wiring the relay mod that there were solid hookup wire remnants on the terminal strips where the switch wires hook up. This proves to me that this set was operated at one point in its history without the use of the on/off switch. In other words, it was bypassed so it could be used by the customer probably while the new part was being ordered etc. Just a hunch but it makes sense.
DAY 374, OCTOBER 11, 2016
Mike continues: I finished making the interface cable for the convergence chassis so the jigging up process is complete. I did an inspection of the tuner contacts and there is a whole new issue there. I see corrosion on some of the contacts which is probably a remnant from some cleaning agent in the past history of the service of the set. I will evaluate that issue more before I declare a proposal on it but it may involve removal of the tuner assembly and disassembly of the drum in order to correct this. I will let you know. My “gut” feeling on it is that the sooner we remove the corrosion, the better. Anyway, please find the pictures. One is of the tuner but it is hard to see what I am seeing from here. Look for the “green” on the contacts. Picture #1 is the convergence cable I made up for the jigging process. Pic#2 is the tuner. Pic#3 is the relay mod and pict #4 is the set running on the jig and showing the convergence problem “re-produced” and ready for troubleshooting. FYI, I may not have any more updates for a few days since we are heading to CA for a few days to attend a wedding. I will however still have internet contact during that time so we can still communicate if necessary. We go on the road on Saturday the 15th and return on Tuesday the 18th. I had a discussion with my son today and he agreed that the rebuild process that you found is the best way to go. So that is settled. I will await instructions from you as that unfolds.
DAY 375, OCTOBER 12, 2016
Author: I am a member of the Videokarma forum. I asked if anyone could help with a solution for the broken fine tuning knob. Bob Galanter offered to repair the knob. Bob is a vintage television collector and restorer from my old home town, Milwaukee. He ownes and restored a RCA 21CT55 which had the same problem. He maintains a website, “Bob’s Antique Televisions’s“. When you view his collection of vintage televisions, you can see he is very knowledgeable and meticulous. He is going to custom rebuild a collar for my broken fine tuning knob and there is a page on his website showing how he will do this. Have a look. Thank you Bob.
More from Mike: I will be sending the knob off to Bob by Friday sometime as I indicated in the recent email. I have an update on issues with convergence. The green static magnet would not bring the green picture into convergence with the red and blue. It just barely does not make the converge. I decided to take a closer look at the pole pieces so I removed the assembly from the jig and took apart the green pole piece magnet assembly only to find that the 1/8 inch diameter magnet that rotates inside the assembly is broken off about a quarter of the way up its length. This explains why it would not quite go the distance to converge. This is clearly step number one in working on the problem. I have removed the magnet from the assembly which you will see in the photos. I then cemented the pieces together with JB weld and used shrink tubing over the repair in an effort to maintain the cylindrical properties of the magnet. I hope it works. After the cement cured, I removed the shrink tubing and then added more JB Weld. I think after a little sand paper on the weld, it may be just fine. Plan B is to purchase 1/8 inch Alnico rod magnet stock and use that for the repair.
DAY 376, OCTOBER 13, 2016
I re-assembled the convergence yoke and mounted it to the test tube and the fix worked for the center convergence. I can now drive the green picture completely through the red picture. A good step forward for the convergence. I now will be able to learn why several of the other controls are either non responsive or out of range. I may not make any more headway on this until next week when I return from CA.
DAY 384, October 21, 2016
Mike resumes restoration: Lots of progress on the old set. The convergence problem is fixed. Now we continue to disassemble the tuner and clean the corrosion from the contacts, then go on to the problem with the hue control and ultimately removing the CRT to clean the safety glass and screen. The hue control problem may be part of the tuner problem so we need to start there. The schematics call this a “5 I.F. ” set but it is really a “4 I.F” set. The 1rst I.F. (at least in my opinion), is really the Tuner Mixer stage. I say that the hue problem may be a tuner problem because it may in fact be a RF.I.F. alignment problem. Let’s only go there if we really have to.
Pix 1 Convergence chassis showing capacitor C21 needed to be replaced. It showed low internal resistance even though it was newly replaced by Dave. I also found qty 5 resistors out of range in the convergence chassis which were replaced.
Pix 2 A shot of the screen of the jigged chassis to an RE21FBP22 CRT with corrected convergence.
Pix 3 A shot of the color bar pattern even though it is not yet the correct spectrum of color.
Pix 4 Disconnecting the wires to the tuner assembly
Pix 5 Removing the tuner assembly
Pix 6 Removing the tuner assembly
Pix 7 Tuner before dismantling
Pix 8 Nut/bolts/screws from removing/dismantling of tuner
Pix9 Fine Tuning slug removal process
Pix 10 Fine Tuning slug removed
Pix 11 Unloading the “detent” on the tuner
Pix 12 Unloading the “detent” on the tuner
Pix 13 Detent removal
Pix 14 Electronic/Contact assembly removed
Pix 15 Corrosion on contacts
Pix 16 Corrosion on contacts
Author: So glad to see the convergence fixed. On the left, the first three vertical lines have a green tint, maybe just a camera aberration. Thanks Mike.
DAY 387, OCTOBER 24, 2016
Greetings Marshall. I finished the tuner assembly and installation this evening. It turned out fine. All the contacts have been polished and lubed and the bearings and detent have been cleaned and lubed as well. I have pictures but I will send them tomorrow. Now on to the color problem. I have not been to the post office in a few days but I anticipate the fine tuning knob is awaiting pickup. I did not get a tracking number from Bob so I don’t know for sure. I may get there by Tuesday or so.
Good evening Marshall. Here are the pictures from the tuner re-assembly. The tuner has actually been re-installed in the set as I stated earlier but here are the pictures of the cleaning and lubing process. I made some slight adjustments on the contacts and I adjusted the detent for proper surface contact of all the strips. Rotating the tuner shaft is now very smooth and positive. Please find picture attachments.
1,2,3,4) Disassembly of gear train and fine tuning control mechanism.
5) Clean and lube main bearings.
6,7) Drum before cleaning and polishing.
8) Drum after polishing.
9) Main contact assembly after polishing.
10) Main contact assembly after lube.
11) Assembly complete.
DAY 389, OCTOBER 26, 2016
Hi Marshall. The color problem is an interesting one. The color bands exhibit changes in color in the color bars from the top to the bottom of the raster. This implies to me that there is some kind of chroma oscillator sync issue but I have not had any time to dig in to it the last few days. I have however found the parts I need (within all my junque’) to replace the peaking coils that I feel are not the correct ones that are in the set now. The ones that are in the set are low frequency, high current and what we want is High frequency and low current for the peaking process to be achieved at the 6 MHZ level for the picture detail. I will start by replacing the peaking coils with the correct values and then take it from there. Also, the fine tuning knob arrived and it looks very good. It fits and will do the job nicely. Thank you Bob Galanter for a nice job on that. Regards, Mike
Author: Here are a few photos of the rebuilt fine tuning knob by Bob Galanter. He epoxy glued a machined piece of aluminum to precise dimensions onto the remaining plastic collar. From this point forward, we will have a strong reliable knob and the three plastic extensions prone to breakage are gone. Good job Bob Galanter.
DAY 397, NOVEMBER 3, 2016
From Mike: Well I took a stab at the color problem this evening and 2 things are glaring at me. One is that the chroma oscillator is “weak”. And the other is that the green image does not shift from the right side of the color pattern to the left as the hue control is rotated. I did some very careful “tweeking” of the tuned chroma circuits and I do not get the expected result out of the burst amplifier stage. I should be able to drive the green portion of the picture from the right side of the screen to the left thus providing a center for the hue control. This does not happen and I’m not sure just why as yet. We are leaving tomorrow (Friday) for CA again. We have some business at the observatory to take care of so I will be away until Tuesday. My time on the road will no doubt give me some time to “chew on this one”. This might be as simple as a failed/poor oscillator crystal or possibly something else in the set that is mis-tuned. The “hunt” is on.
DAY 402, NOVEMBER 8, 2016
From Mike: Greetings Marshall. I have good news. I have found a failed component in the chroma circuits. I found that there was no evidence of the burst amplifier signal at the input of the 3.58MHZ oscillator. I traced the problem to a peaking coil (L41) in the Sams Photofact schematic. The coil was OPEN with infinite resistance!!. YAY. After I replaced it I found (without surprise) that all of my tuning that I had done was way off!!! This is a very positive thing in the progress of the chroma problems. I am not out of the woods yet, but this is obviously a very good find. With a few minor adjustments of my tuning of the coils I am now able to change the HUE. It does not go the full way that I would like yet, but this is very promising. I think that the next step for me is to connect the set to a real NTSC signal from a modulator and display a picture from a DVD player. This will give me the precise position of the fine tuning control and also give me a good idea as to what the real picture looks like with color.
Yet to do after this is totally resolved:
1) Replace the remaining peaking coils that are the incorrect values.
2) Replace ALL other peaking coils that may give future failures even though they have not failed.
3) Replace the CRT socket that I previously declared to be failing.
4) Do a detailed chassis clean.
5) Remove and re-install the CRT and clean the face and faceplate.
6) Re-install the chassis and do a full purity/convergence/focus/greyscale setup.
We will leave item #7 for future declaration, if there is one.
Regards and cheers, Mike
DAY 408, NOVEMBER 14, 2016
From Mike: Greetings. Some progress on the color problem. First of all, I replaced 2 tubes which checked perfectly good but had issues. The 3.58MHZ oscillator and control tube had some kind of problem, probably capacitance issues within the tube which is not normally detected on tube testers. The other was the burst amp keying tube. Both changed the tuning of the circuits significantly. BUT, the final thing that made things come together was L31 in the output of the Video Amp circuit. It is the coil that tunes the resonance of the HUE control variable capacitor. Now I have a LOT of control of the HUE whereas before, I had SOME of the control. A very significant breakthrough. The Burst signal at the input of the 3.58 oscillator got a lot stronger when I tuned L31. This made the difference with the oscillator being stable with different signal sources. I have attached a video of me turning the HUE control as the spectrum of the screen changes. It is very positive control now. I feel as though there are still issues with the R.F.I.F. alignment. I do not like the way the fine tuning moves in to where the color signal should be, that is to say, on the “high” side of the oscillator. There is a lot of color rainbow and other things like oscillations that I do not like. So, off to the alignment workbench next. It will be interesting to see what the alignment curve looks like. I suspect that a 41.25 MHZ or 47.25 MHZ traps have drifted or are mis-adjusted. My goal is to be delivering this set back to you by mid December if all goes well. I am very happy with the progress so far.
As I was trying to attach the file I was told that it exceeds the 25 MB size limit. I will try to send it from my other email account. Watch the video.
Good evening Marshall. I’m glad that the video came through OK. I should clarify some things. The Hue control that I had working a few days ago was in indeed “working”. This came to be after I found the open peaking coil ( L41) at the input of the 3.58 MHZ oscillator and that led to me re-tuning some of the chroma circuits to make the spectrum “somewhat” correct. When doing so, the technician is trying to accomplish two things. 1) proper spectrum and 2) proper Hue shift of the spectrum. At that time I had achieved spectrum that was “close” and hue control that was “there” but it did not have enough “shift” of the spectrum to satisfy me. When we ( I ) take on these vintage restorations we cannot assume that any of the guys before us knew what they were doing so at times it becomes a real “witch hunt”. That is what I am faced with on this set. The Hue control resonance coil that I “tweeked” to give the Hue its range yesterday was off by about 6 turns. That means that someone ahead of me was trying to get the circuits tuned with a failed component ( L41 ). I took a shot in the dark when I decided to try moving L31 by so many turns to make the Hue control do the proper shift of the spectrum. When I did, the chroma sync got stronger at the oscillator which solved the problem that I described about poor color sync with the modulator hooked up using a DVD player. I think I used the term HHM.. HHmm because I was puzzled about those results at the time it happened to me. Now I understand what was going on and it leads me down another “road”. That road is one of anticipation that there are other tuned circuits that have been “tweeked” by people that did not know what they were doing. Hence, my statement about questions of R.F.I.F. alignment. Things like the “color rainbow” patterns superimposed over the actual color picture can only mean issues with alignment of some kind somewhere. This is not a “course” rainbow pattern but a “fine” rainbow pattern as if it is a “harmonic” of the 3.58MHZ fundamental frequency used by the chroma circuits.
I feel as though I am in the home stretch with the repairs. The last couple of days have been very productive with the Hue control working over its wide range the way it should and the spectrum being very close to what I expect. The first stage of doing an R.F.I.F alignment is always to look at the alignment curve first before making any adjustments. Often times, this will tell you immediately where the problems are and you can correct a serious problem with only a couple of adjustments.This is where a lot of technicians fail with their habits on adjusting things. The video curve is 6 MHZ wide and the center frequency is 44 MHZ. The video carrier of 45.75 should be at 50 % up from the bottom of the curve on the upper sideband and the Chroma carrier of 42.17 MHZ is (typically) at 50 % on the lower sideband of the curve. The traps for adjacent channels are at 47.25 MHZ and 41.25 MHZ. This curve repeats for every channel on the dial and the mixing of the necessary frequencies to make it all happen takes place in the tuner mixer circuits.
R.F.I.F.. alignment is an art. BUT, it is not rocket science! It takes a lot of practice and I have done a lot of it. I have probably done more than 500 of them in my experience working on television sets both B/W and Color. Color is definitely more critical. There are many methods and they all require the same equipment and the end results are the picture quality improvements. The first 10 or 15 alignments that a person does when they are learning the art are very scary. I remember mine very well. (you can laugh out loud now) I was very fortunate to have a good instructor who knew how to explain things and answer questions very well.
I will be thinking about the fan idea and the castors idea. Voltage regulation in my opinion is not an issue.
Best regards, and back to the work bench, Mike
DAY 415, NOVEMBER 21, 2016
Hi Marshall. I have been looking over all circuits of the chassis in a HUNT for peaking coils that “look” like they could fail. The clue is a small part of corrosion where the wires meet the potting. The corrosion looks a lot like what I found on the tuner contacts (for whatever that may be worth). Anyway, I found 3 more possible future failures tonight. So far I have spares for all of these. The ironic part of this process is that changing the parts has no affect on performance because the parts have not failed yet. This is the “preventative maintenance” part of the repairs. I will finish replacing these peaking coils over the next couple of days. I have cleaned off the bench where the alignment equipment is so that part of the shop is ready to go. The CRT socket still needs to be replaced and I have a good used one here all ready to install. When I get the chassis hooked up to the alignment equipment I will try to get some good shots of the curve as it is displayed on the oscilloscope (if I can) It would be a good thing for you to see especially if I have to do the alignment because you will get a “before” and “after” picture of the results.
DAY 416, NOVEMBER 22, 2016
Greetings Marshall. I finished the peaking coils tonight. Yay! I think I got them all. It was both visual in to the chassis and also data taken from what the parts list calls out as peaking coils. A couple of them had the usual corrosion at the point where the wire meets the potting. This is very typical for sets of any brand at this age. We nabbed it. I also replaced the coils that I previously called out as “in my opinion” were not really the right ones. They were high current, low frequency coils and they really should have been low current high frequency. The difference between the two is the size of the wire with which they are wound. Fine wire for high frequency equals peaking effect for the signals. These were heavy wire which would be for noise suppression at low frequencies. They have been replaced. I hope to take a look at the I.F. curve tomorrow evening.
DAY 417, NOVEMBER 23, 2016
SWEEPING THE I.F. ON A CTC2B
Greetings Marshall. The I.F. curve is a real mess, just as I suspected. It is amazing that we are getting any color signal through it at all! I have not “tweeked” anything yet but I will be doing so soon. I want to absorb what I see for a couple of days and look at the curve a couple of more times just to make sure that it “repeats” with the equipment. I am very sure that it will based on how easy the set hooked up to the alignment equipment. I connected the output of the sweep generator “loosely” with a loop of wire into the Mixer stage of the tuner. This is the 1rst I.F. according to the schematics but it is really the Mixer stage of the tuner. Then I connected the video output of the set to the equipment. The final step was to control the gain of the I.F. strip with bias on the grids. Then I had my curve.
Picture #1 The alignment “bench”
Picture #2 The “hookup”
Picture #3 The sweep alignment curve
Picture #4 A closeup of the curve.
Picture #4 tells a detailed story. The 47.25 MHZ trap on the right side at the bottom of the sideband looks good. but I will check it anyway during the process.
The 45.75 picture carrier on the right side of the sideband is not perfect but it is close.
The 44.0 MHZ marker shows up half way down on the lower sideband which is absolutely terrible. It should be in the center of the curve at the top.
The 42.17 MHZ CHROMA carrier is OFF the BAND on the LEFT and is difficult to see because I think the 41.25 MHZ trap is shown as the sharp “dip” on the left, which is essentially “trapping” the chroma signal.
This is actually all very good news because it does further explain why the fine tuning control responds the way it does. Please find attachments.
DAY 419, NOVEMBER 25, 2016
Greetings Marshall. I have found a problem with the first stage of the I.F. strip. The 1rst I.F. grid transformer (T106) does not tune properly. There are 2 cores in it, one for the top and one for the bottom part of the transformer. The one on the top does not tune. Ironically, it is one of the 41.25 MHZ traps that I mentioned in my previous email. I suspect that the powdered iron core is sitting in the bottom of the coil and has become separated from the screw that is normally attached to it and positions it in the coil core. This will be a very delicate piece of surgery. The transformer will have to be removed from the set, disassembled and examined. There are 2 possible scenarios here. Scenario one is that I can successfully repair the coil and scenario two is that I cannot. I will not know until I “go” there. If I cannot then I will have to build a circuit that will take its place using newer materials possibly from a newer chassis. Theoretically, this stage could be mostly eliminated since there are traps of the same frequency in the last stage of I.F. to do the job.The purpose of the 41.25 MHZ trap is to trap out the adjacent channel sideband and since you will be using a modulator to view images it makes this issue a lot less critical. But I really want to do this right and fix the transformer if I can. It is hard to say when this actually happened. It could have happened on its way across the country while in the truck or it could have been that way for many years and picture quality was unknowingly sacrificed. Either way, I am very happy to have found this problem. Now I will figure out how to deal with it. Hopefully I will have some images of a very improved I.F. curve soon.
DAY 421, NOVEMBER 27, 2016
In an effort to assist Mike and to avoid the “surgery” we requested help from the VideoKarma forum community. Kevin came through and cross referenced this sub for the RCA part # 78987 which subs to Thordarson Meissner 17-4518. THANK YOU KEVIN!
From Mike: Greetings again. Well, I removed the transformer and disassembled it and it looks like I called the shot well. The core was in the bottom of the coil form with pieces broken off inside the form. I have sent 6 pictures.
Picture #1 shows the “can” to be removed and the adjustment screw on the top for the 41.25 MHZ trap adjustment.
Picture #2 is the bottom shot before removal.
Picture #3 is “always draw a picture before removal because you cannot always trust the schematics.”
Picture #4 is “I.F. Can removal.
Picture #5 is the “can” disassembled showing the core broken away from the adjustment screw.
Picture #6 A picture of the core and screw closeup.
I have purchased a new transformer by way of ebay “thanks to Kevin from VideoKarma” for cross referencing this item and doing the research. RCA part # 78987 subs to Thordarson Meissner 17-4518.
I can repair this transformer if necessary, but I will wait for the delivery of the NEW OLD STOCK part for now. I can use this time for replacing the CRT socket which is still “on the list”.
DAY 424, NOVEMBER 30, 2016
From Mike: The CRT socket has been replaced. The main problems with the original socket are 1) some corrosion on the pins. Not bad corrosion, but not good to leave that way. 2) the insulation on the focus wire is failing where it goes in to the socket. I consider this repair preventative maintenance. I have found a socket in very good condition from a CTC5 parts chassis that I have and that is the one that I have installed. The replacement I.F. transformer has left South Dakota as of this morning so I should have it here in a couple of days. I have investigated the cleaning of the crt and faceplate and MAYBE I will not have to pull the CRT. It looks like RCA provided QTY 8 clips on the inside of the cabinet that allow me to remove the safety glass for cleaning. Not sure yet, but I will know soon. I will have someone help me with the removal of the “trim” on the front if these clips do in fact allow such a nice way to clean the crt face and glass. I will take care to make sure that there are no surprises awaiting like the glass suddenly becoming loose while I remove the clips. Picture #1 old socket and Pictures #2 and 3 “new” socket from CTC5 parts chassis.
DAY 427, DECEMBER 3, 2016
From Mike: Greetings. I removed the safety glass this evening and cleaned the CRT face and the glass. I was happy to find that the brass trim was attached to the glass with a gasket type of material and that made things a lot easier to deal with. It all stayed “together” quite well as an assembly. I found that there were only QTY 8 clips and not QTY 10 to hold the trim in place. The clips on the sides were not there as if someone had removed the glass previously to clean it and did not re-install those clips. Not a problem as far as security for the glass, just a note on my part. The replacement I.F. transformer is now in Las Vegas and should arrive in my mailbox by Monday. We will be back on to the I.F. alignment bench soon.
DAY 429, DECEMBER 5, 2016
From Mike: Good news. I received the new I.F. transformer today and it is an exact replacement. All pin configurations were the same as the old one. Thordarson Meissner company did it right!. I replaced a couple of resistors and capacitors that connected to the new transformer as a result of the installation. A new alignment curve from my rough adjustments is very promising. I will of course, go through the entire procedure as handed down from RCA just to “see” if it varies from my first results. The main thing I will pay attention to is the adjustments of the co-channel traps for picture and sound. The rest should be mostly from what I see on my equipment. The pictures that I show indicate a nice 41.25 MHZ dip on the left side of the curve. This is the adjacent video trap that was not previously working and the sound carrier for the FM. Half way up on the left is the CHROMA signal of 42.17 MHZ. Next in the middle of the waveform is the center of the 6 MHZ wide video signal of 44MHZ. Next, down half way on the right upper sideband is the 45.75 Video carrier and finally on the far right is the 47.25 MHZ trap for adjacent sound. This waveform should produce a good B+W picture and ultimately a good color picture that tunes properly on the “high” side of the tuner occillator when the fine tuning is adjusted. 3 pictures are attached. The second picture shows the frequency markers vertically on the waveform and the 3rd picture shows them horizontally to make them easier to see. Enjoy.
DAY 430, DECEMBER 6, 2016
From Mike: I went back to the alignment bench tonight and started by checking all of the trap adjustments. I found that there had been some interaction with the trap adjustments that came from my experimental “tweeking” the night before. Not a surprise at all. These coils and transformers always interact to some degree. So, after touching up the traps I went for another alignment curve and the result was “textbook” curve, very nice. After that I went after the traps again and touched them up again. I went through this probably 4 times. The curve looks very good now, as good as it can possibly be. Please find attachments. Tomorrow, it goes back on the jig for more evaluation and hopefully “finish” tweeking of the chroma circuits.
DAY 432, DECEMBER 8, 2016
From Mike: Well, after some more screwing around with the chroma tuning, I am getting close here. There is some interference (snow) in the image but it is not in the set. I see it on all my TV’s around here and I have not found the source for it yet. It is very intermittent which makes it hard to track down. It might be a ham radio operator running a lot of power. Anyway, it should be ignored for now. There is also some “morie’ ” effect that is only a result of the way the camera clocks out the pixels for the image and that is not really in the true image. Enjoy!
I am really happy with the way the I.F. alignment came out. The images are very sharp on the 21FBP22 tube.
DAY 434, DECEMBER 10, 2016
Hi Marshall. I got the blogs but they did not really tell me what I need to know. If I get time tomorrow I will give you a call so we can talk about this part of the restoration. I know about the chimney on the cage and that makes the most sense to me, to remove it an install a fan there. The power for the fan is easy since I installed the relay modification. It gives us the switching power we need to do the fan and keep the load off of the on/off switch. As soon as I can do this mod I can install the chassis and give it at try on the 21AX tube. I fired it up again tonight and watched a full hour of Bonanza and tapped and “pounded” on the chassis looking for intermittent problems and it was solid as an old rock. A very good test. I call it the “drop” test.
DAY 436, DECEMBER 12, 2016
From Mike: Greetings. The fan install took longer then I expected. The chimney cap was removed by cutting away at the electro-welds with a Dremel tool. This makes it possible to “undo” the fan project if we ever want to do so. No real damage has been done to the chimney cap and it should be saved. The first picture shows a real nice “salt and pepper” snow with no signal. This is indication of good R.F. I.F. response. The rest of the pictures are the fan modification. The fan was mounted so that it “pulls” air from the bottom of the chassis rather than from the top blowing down. If mounted the other way, it would be blowing air from the top and adding heat to the flyback from the tubes.
Author: Hi Mike,
Nice neat, clean fan install. Nice forethought to restore the chimney if need be, which I doubt. Are those rubber grommets I see to reduce noise and vibration? Do you plan on testing the fan efficiency on the flyback by touch? Just as you predicted, salt and pepper noise with no signal.
DAY 444, DECEMBER 20, 2016
Greetings Marshall. I had another surprise tonight. I was doing a last check on the jig when I noticed some “hissing” going on. It was coming from the high voltage cage. I guess I found the “corona” that was reported by Dave. The connector on the High Voltage regulator tube (6BK4) is in terrible condition. I looked at this earlier when I was installing the fan but it did not look “that bad” to me. A closer look when I noticed the arcing (corona) indicated that this connector needs to be replaced. Also, I decided to turn off the lights and take a closer look inside the cage with the room totally dark. There is also some arcing going on at a series of 2 watt resistors in the focus circuit. These are a set of qty 6 resistors with values of 10 megohms each that make up what is supposed to be a single resistor of 66 megohms. The original resistor was a film type made especially for high voltage circuits and it has been replaced with a series of carbon type. OK, now, electrically it is the same thing when speaking of “ohms law” however, for high voltage applications this should have never been installed this way. Essentially, the way they are installed provides for a possible 12 more points to cause corona as opposed to 2 points if a single resistor of the proper type were to be used. THIS SORT of thing is what causes flyback transformer failures! So, my plan is to replace the connector on the top of the 6BK4 and to also replace the resistor network with a single value. I found the part I need in one of my CTC16 parts chassis for the resistor and I have a good plate cap for the 6BK4 from my pile of “junque”. I am glad that I found this potential for future arcing so we can nip it in the bud. I think this showed up because the humidity is a little higher tonight so that is a good thing. Please find pictures. The road continues.
Regards and Merry Christmas
Going camping again tomorrow and will return on the 24th.
Mike, Just wondering, was the new fan hooked up and running when you saw the corona? Could the fan addition have something to do with it? If the fan was running, could it blow something into the cage?
Mike: Good morning Marshall. As it turn out the fan had been running for a couple of minutes. So yes, it could have played a role in the startup of the corona i.e. a small amount of moisture entering the cage. Either way, it is a good thing that it happened. IF I think that the fan will be causing troubles then I may decide to install a small switch inside the top cover for you to switch it off if you wish. What do you think?
DAY 449, December 25, 2016
Greetings and Merry Christmas. I finished the wiring repairs of the high voltage and focus rectifier circuits tonight. I have not yet re-installed the cage cover. I will do that tomorrow and test again on the jig tube. I have included pictures of the latest repairs.
1) Overall of the cage wiring before repairs.
2) The mess before repairs. Note the Brown/Black/Blue string of resistors and the series parallel string of Yellow/Violet/Green resistors.
3) The new parts installed (66 Megohm film type with the stripes) and 2.7 Megohm film type in black shrink tubing to the right of it. Also, a new high voltage wire (red) connecting to the focus rectifier tube.
4) High voltage rectifier tube socket disassembled (lower left). This is where the new high voltage cap connection will be installed for the regulator tube.
5) High voltage rectifier socket re-assembled with new cap connector.
6) Overall view of repairs and tubes cleaned up.
Tomorrow, back to jig testing and then hopefully a test in the cabinet.
Merry Christmas, Mike and Barbara.
DAY 450, December 26, 2016
From Mike: Tonight I installed the high voltage cage covers and since the humidity was 70% in the shop I decided that it was a good time to do a test. Thanks “mother nature” for the recent 7 inches of rain! I fired it up on the jig with the fan running. The outcome was great. NO corona!!. All of the repairs were a positive outcome. I am very happy with the results. There are 12 less points (at least) for potential arcing within the cage and the resistors have been replaced with original values that are rated at the working voltages. I have also installed a switch on the fan so that it can be disabled if desired. Tomorrow I will do one last trip to the alignment bench to make sure that all is well and then it will be time to install it into the cabinet and once again, light up the 21AXP22 and begin a new complete purity, convergence and gray scale setup. I never did find an answer for the problem that I had the last time I installed the chassis. The multiple images and no color problem is still a mystery at this point.
DAY 454, December 30, 2016
Greetings Marshall. Tonight I decided to take a new approach and it appears that it has proven successful. I went after the I.F. strip with a magnifying glass and a lot of light on the bottom of the chassis. I looked at every I.F. stage pin by pin. Bingo! I found a flake of solder on pin number one of the third I.F. stage tube socket. It was barely touching chassis ground. It was very small but obvious with the magnifier and light. It is amazing what a small piece of LEAD can do, even on a small scale relative to gravity. I do not have a photo of it. It would have been too small to photograph easily anyway. A quick re-test on the alignment bench showed a good curve so we are back to where we need to be. YAY!!! I installed the chassis into the cabinet and the picture is sharp with good color. I only did a ROUGH convergence in order to get things going. But the first light on the CRT is very nice in my opinion. I now refer back to where I had to remove the deflection yoke in the very beginning of this long march. I made mention of “body and fender work”. Not a big deal really, just some JB Weld in the right places to re-connect the magnetic shield that exists between the deflection yoke and convergence yoke. This shield really is not necessary in the real world but since it is part of the original equipment, I am returning it to its natural state. I will be doing a full setup on this tomorrow night if all goes well. Please find photo attachments of the yoke restoration.
Day 456, January 1, 2017
Happy New Year. I did a rough setup tonight. The convergence on the left and right is not as “tight” as it was on the jig tube so, I must attribute that to the 21AXP22. I may be able to get it a little better but that is it for now. My camera is not the best for images like this so things like the brightness and focus may not be the real world. I am very happy with the DETAIL in the images and the color spectrum considering the year in which the set was made. I will say that this particular 21AX is the best one that I have seen as far as focus tracking within the 3 guns and in general, very good for a metal tube. I will play with the color temps and convergence a bit more over the next few days and generally give the set a good “cook”. The humidity in the shop was 75% tonight and I had the fan running. There was no sign of corona which makes me very happy as well. The work inside the HV. cage was good stuff to do. The small splash of solder that I found on pin one of the 3rd I.F. could have been there for many years. It probably came from a repair done by any technician in the history of the set. Those things happen. And I am glad that the problem showed up for me when it did although it was very strange the way that it would change from one workbench to the other. Anyway, please find the most recent photos of the chassis working on its original tube. Long may she run.
Really great “preliminary” images Mike. Shows very good detail for a set of this age and it’s limitations. I have sent you a reference screenshot taken from an ISF calibrated monitor. The preliminary image on the 21AXP22 looks to blue. We need to set the color temperature to something closer to the ideal 6500 Kelvin if possible.
DAY 458, January 3, 2017
Greetings. I did some more adjusting of temps and convergence. I have done all I can for now. Any more adjustments will be made upon delivery and hopefully that will be minimal. The camera I used for taking the pictures seemed to have focus issues and was more difficult than usual and I was getting tired but I think you understand that the images on camera do not lend justice to the real picture. I have installed all of the chassis bolts and next is to work on the cabinet a little as we discussed. This old set is still very robust this evening. It starts right up and runs. Only a short warmup for focus and reasonable gray scale. These images are from the John Wayne movie Hondo which, of course are not color enhanced. I am happy with the performance of this set and I do not feel as if it could ever work any better than it does now. It may be better now than it has ever been. Enjoy the shots. See you soon.
Author: Very nice Mike, these shots once again, show very good detail. This movie was released in 1953 and filmed in “WarnerColor”. The only problem with Warner’s CinemaScope pictures was the fact that they continued to use their own WarnerColor lab for several years, sending out the worst looking prints in the history of motion pictures. By the mid-50s, Warner’s shut down their lab and went exclusively with Technicolor. The difference in the look of Warner product was very obvious, with the studio releasing some of the best looking films to come out of the Hollywood studios during the last decade and a half of dye transfer Technicolor.
I compared your shots with YouTube videos of this movie on my iPad. Not much better color quality. I can’t wait to see it up and running in my home. Is the set producing reasonably good reds?
I consider the reds very good for this set. There is lots of color if you want to turn it up. I tend to go with less rather than more on color controls. And the hue gives you the normal range using the skin tones as reference. Everybody sees color differently and I may have to do some adjusting for your eye when I deliver it. The reds on the horses and on John Waynes’ kerchief are examples of the red response. The Rare Earth tubes were definitely better for the red response so there are limitations with this technology. The brownish color of the horse is a result of the Luminance (B+W) signal doing the proper mix with the Chrominance (color) signal to achieve the brown. The red in the kerchief stands out well I think for the red alone. The skin tones which shown close to natural here, (John Waynes face is dirty) and the woman’s face has much more pink in it by contrast with his face. All these things indicate to me that the reds are doing what we expect. Also, there is a game we play with crt’s of this type in order to achieve the proper gray scale. The red plays a very important part in the gray scale and these crt’s typically do not track well for gray scale so the temp adjustments are best made at the brightness level at which the set is going to be watched. Then the game turns in to a balancing game with colors and brightness levels and a “happy medium” has to be met.
For comparison purposes we found a screenshot from a full restoration 1080p/AVC MPEG-4 encoded BluRay disc captured on a modern flat screen television. Initially after seeing Mike’s screenshots, I thought the red gun was weak or the 21AXP22 color phosphors were incapable of displaying red properly. John Wayne’s bandana looks orange and blue on the 21CT55, but it turns out that the remastered disc also displays the bandana in orange. All photos and posters found on the internet, show the bandana in orange and blue. I believe with minor adjustments and a reduction in the brightness, we can come close to the below screenshot. Bear in mind, the 21CT55 is a 62 year old television and Mike’s comments that the camera did not accurately capture the true color image.
DAY 470, JANUARY 15, 2017
The restoration of the RCA 21CT55 is completed! Mike and his son, Mike Jr. delivered the set today. We did the final setup and adjustments about 20 feet from its final location allowing more space to work with.
Here, a shot of the new fan installed over the high voltage chimney. There are rubber grommets to isolate vibration. The fan can be heard, but the sound is not obtrusive. Mike installed an on/off switch on the fan if I want to turn it off for any reason.
This is the new yoke cover which came from an RCA CTC-16. You can also see the general chassis clean up. Mike also removed one major scratch on the side of the cabinet. The only thing I need to do is brighten up the brass arond the safety glass. This will be done by hand.
A few preliminary screenshots. The first, the set next to the CTC-7 Worthington. The second is Steve Cross from CBS 60 Minutes interviewing President Obama five days before leaving the Whitehouse. In the past I have noticed the excellent color fidelity of one on one interviews on this show. Mike did a full IF alignment on the 21CT55 and the very good detail shows in these screenshots. In the short time I have had this set after delivery, I think there is still too much blue in the overall images and I need to turn up the gain on the green gun because the grass on the field of the Packers/Cowboys game looked yellow brownish. I had the game on our flat screen. The green grass of the field was not a robust green but was there in the telecast. I will perform this myself. After moving the set about 20 feet to the corner of the room and reattaching power and the digital converter box, I noticed electrical interference which shows up as white “speckles” on the screen. The screen was free from this interence 20 feet away. I need to isolate and remove this. It is minor, but can be seen close to the screen.
A few more screenshots all photographed on January 16, 2017.
It has been a long haul, 470 days since purchaseing the RCA 21CT55. Was it worth the time, effort and expense? Absolutely, a resounding yes! The RCA 21CT55 is part of American television history. It holds the distinction of being the first 21 inch color television offered for public consumption. It was available in limited quantities in time for Christmas delivery in 1954. In our research we found virtually no advertising of this television. This color television was the only RCA color set not given a name such as “Merril”, “Worthington”, “Canton” or “Bremanger”. In my view this television was a test bed for upcoming 21 inch RCA color televisions introduced in larger quantities beginning August, 1955 and beyond. You may have noticed in our restoration chronicle that this television was used as a “professional” studio monitor during the very early days of television broadcasting production, both in New York City and Los Angles, California. According to the Early Television Foundation, only about 3000 of these sets were manufactured and production lasted about 6 months. That makes this television even rarer then the first color television, being the RCA CT-100. Our set is 1 of about 38 known to exist. We derive great satisfaction and pride in being the custodian of this piece of television history.
I want to thank the following individuals for their help in the restoration of this set. First Steve McVoy from the Early Television Foundation who sold me the set and provided the needed tube replacements. I know my purchase went to a good cause. The Foundation is a non-profit organization. I want to thank Dave May who did the initial restoration and Anthony from Pac Mail who did the excellent crating of the set for its journey to me in Arizona. I want to thank Bob Galanter who provided the new fine tuning assembly. I want to thank Kevin from the VideoKarma forum community for helping with cross referencing and a lead to finding the part needed in our IF stage and Walter, also from VideoKarma for his help with the power switch problem. I want to thank Barbara Doyle for her patience. Her husband Mike, spent over 44 hours restoring the television. I want to thank their son, Mike Doyle Jr. for help on the final delivery today. It was nice to meet you and lastly, I want to thank Mike Doyle for all his help since the day he picked up our television on September 26, 2016. He did a superb job, documented everything and addressed all my questions and concerns. Thank you very much my friend and as you said, “long may she run”.
I hope this chronicle will help other hobbiests and serve as an inspiration. We hope you enjoy our time capsule of broadcast television and celebrity as expressed through the screenshots following.
Update, January 20, 2017
In an effort to improve the green saturation and reduce the strong blue tone, we adjusted the green and blue gain controls as well as the green background control. This was done to maintain accurate grey scale. Thanks Mike for your suggestions. Below screenshots showing the results after adjustments. The camera shots don’t do justice in capturing the quality of the actual images. Tap any image to see an image carousel with enlargements.
Tribute to Mary Tyler Moore who passed away January 25, 2017. The below screenshot from the RCA 21CT55 was captured during the program which aired on CBS, January 26, 2017.
Update, January 29, 2017
Miss Universe broadcast live January 29, 2017 as seen on our RCA 21CT55. Watch the short video.
Watch an Original Star Trek episode on the RCA 21CT55. Watch now.
The yellow color contamination in the form of banding and the moire interference visible in some of the screenshots are artifacts of my camera which is a non-pro iPhone 6 Plus first generation camera.
UPDATE, FEBRUARY 3, 2017
New screenshots of the 1967 movie, El Dorado, starring John Wayne. Also screenshots from the original Star Trek series to show the red capabilities of the 21AXP22 and miscellaneous shots. Added February 12, 2017, Grammy award show screenshots. Signal source, over the air digital, convertd to RF analogue and photographed on the fly with no freeze frame ability, using an iPhone 6 Plus.
UPDATE, FEBRUARY 26, 2017
New screenshots captured from NBC’s 90th anniversary special on February 19, 2017, including the infamous Tina Fey Saturday Night Live sequence, “I can see Russia from my house”, as well as the 1955 Technicolor film, “Gentlemen Marry Brunettes”, starring Jane Russel, a take off of the movie, “Gentlemen Prefer Blondes”. Also a shot of John Wayne in the 1976 film, the “Shootest”, his last movie. A shot from the television series, Manix, two shots of Johnny Carson and Christi Brinkley from the March 1, 1985 airing of the Tonight Show and lastly, a couple of shots from the television series “Man from Uncle”. This episode was number 22, season 3, originally aired February 17, 1967. This episode is just over 50 years old, captured February 21, 2017 on a 62 year old television! I think the clarity of this Metrocolor episode is amazing for its age and the clarity still evident on such an old color television. The 1955 movie is showing its age and we tried to capture the vibrant colors.
Additional screenshots from the Tonight Shows, 1974 and 1977, the 1955 Technicolor movie “To Catch A Thief” starring Cary Grant and Grace Kelly, and the 89th Academy Awards presentation show.
UPDATE MARCH 15, 2017
Movie Review: The Red Shoes 👠🎭🎟🏅
The Red Shoes is an English three strip Technicolor production from 1948. The film we are reviewing is a DVD standard definition, in 1.33 to 1 format. It can be enjoyed on both a modern HD widescreen television as well as your old color “roundie” television. We will say right from the start, this is a must view, 5 star movie. The color is lush and sumptuous and at the same time subtle without being garish. We are taken on a journey through beautiful Europe with scenes of London, Paris and Monaco. We follow the young ballet dancer stage performances with soundtrack provided by the London Philharmonic Orchestra.
Being part of the television collector community, the movie “Wizard of Oz” is considered to be the standard movie to judge old vintage color television color quality. Oz is indeed a great film, but for this viewer, our newly discovered movie “The Red Shoes” sets a new standard in technical color quality. The film was fully restored, all three strips in 2010. The DVD gives a full explanation complete with a color booklet describing the movie, cast and special features. This film should be part of every enthusiasts collection and is part of the Criterion collection. Go grab it. Movie review here and here.
From IMDb: “Technicolor founders Herbert T. Kalmus and Natalie Kalmus considered this film the best example of Three-Strip Technicolor. During the filming, however, Natalie Kalmus often complained that Jack Cardiff wasn’t following the rules laid down for Technicolor films and demanded that they re-shoot various scenes. But Michael Powell always backed up Cardiff and they got the film they wanted.”
Watch the entire ballet of “The Red Shoe’s as seen on the RCA 21CT55 color television. View now.
UPDATE, MARCH 28, 2017
We have green! and a new “Dorothy” reference screenshot.
So we went out and purchased the old version of Joe Kane’s Video Essentials on DVD. We have the Blu Ray version, but it was not compatible with my current DVD player hooked up to the 21CT55. Using the supplied blue filter film, we calibrated the blue gun of the 21AXP22. If the color decoder is working correctly, the other two colors should “fall into place”. Our green gun was not displaying green as well as it should and in our latest adjustment/calibration, we took a different approach. This time instead of increasing the green gain, we decreased the green gain and increased the green background controls to get proper color balance on the SMPTE-C color bars displayed by the DVD. This greatly improved the green reproduction on the various programming we viewed after the calibration.
We tested using the Wizard of Oz, The Red Shoes and Gentlemen Prefer Blondes, all great Technicolor films. The recently discovered Red Shoes film from 1948 is a gem of a movie to evaluate an old color roundie television. The color is simply beautiful and there is one scene in particular that replicates the standard “Dorothy” facial shot from the Wizard of Oz which many collectors use to judge their televisions. The color tones and gradations are superior in this authors opinion. The scene we are referring to is the lead actress in the film. We will be using this movie, The Red Shoes, to evaluate current and future color televisions in and for our collection. Below, the first screenshot is what we call the “new Dorothy reference screenshot”.
UPDATE, APRIL 10, 2017
A tribute to Ed Reitan about his restoration of the 1958 NBC color television special, “An Evening With Fred Astaire”.
UPDATE, MAY 16, 2017:
We shot a video which is posted below. Tap on any image for enlargements.
UPDATE, OCTOBER 31, 2017:
We were doing a video of the 21CT55 and it was running continuously for about 4 hours. We left the set running alone for no longer then three minutes and after returning, found the horizontal collapsed about one third of the screen, badly converged color, and out of focus. No unusual sounds or odors present. WHAT THE HECK HAPPENED! After much testing, we thought the flyback failed. The set was only producing 10KV. More testing with the HV probe and we pulled the regulator tube and found the HV was at its full 20KV. That led us to suspect a resistor in the HV regulator circuit. We tested it and fond it “open”. The suspect resistor was “buried” under the damper tube. This was done at my home and with lack of proper test equipment, off the chassis went once again to Mike’s test bench/shop.
Greetings. I installed the new resistor into the HV. regulator circuit and jigged it up tonight. I now have good control of the High Voltage with the adjustment. It regulates between 18 KV and 21 KV as it should. The raster is full, the focus is good and the convergence looks reasonable for being on the jig. You are a lucky man! It appears that the flyback transformer is OK. No photos tonight, it got too late but I will be taking a careful look at the Chroma circuits within the next couple of days to make sure that I have not missed anything, mainly looking at the complaint of lack of Green. Anything is possible at this point since this chassis seems to be full of “surprises” with its early color television circuitry.
Greetings. I have done more testing tonight in an effort to identify any issues with the chroma circuitry and paying special attention to the green. All voltages and waveforms looked acceptable. After the testing, the “technician” in me decided to do some “empirical” adjusting of some of the transformers in the chroma circuits. When doing these things, one must be VERY careful to go slowly unless “he” wants to start all over again with the procedures to get things aligned. When I got to L44 ( the Quadrature Transformer), I adjusted the slug out about 1/16th of a turn CCW and the green got stronger on the right side of the raster. All I can say, is, maybe the trip on the road caused the slug to settle a little inside the coil form. This adjustment made no difference in the voltages anywhere but it did improve the green “strength”. All I can say is, “whatever works” and I will not argue with success. This should, I hope, make in improvement in the green response even though the CRT is a bit tired. I have included photos of the resistor I found in the High Voltage Regulator circuit which was causing the reduced high voltage condition and hence the shrunk raster, out of focus and poor convergence symptoms. The High Voltage was reduced to 10 KV with this failure. It now adjusts nicely from 18 KV to 21 KV as it should. The resistor was an original (made by International Rectifier) special film type, 3.4 Megohm 3 watt. I replaced it with QTY 2 (in series) OHMITE 2.2 Megohm 2 Watt film type which now makes the new resistor a 4 watt unit which is a 25% upgrade for power dissipation. I will be cycling this set for a few days. Please find photos of the resistors and color bars. Please ignore purity issues.
All I can say is the failure was a blessing in disguise. After re-setting the grey scale and doing a complete new setup, the green output is strong now and all the other colors “fell into place” as they should and now look very accurate. It looks like a totally different CRT was installed. Great work Mike and indeed we are very lucky it was only a resistor causing the HV problem. The failure gave you an opportunity to revisit and take a “second look” at the chroma circuits and adjust that slug. I will post a few photos of the offending resistor, it’s location and it’s replacement together with a few screenshots.
UPDATE, NOVEMBER 7, 2017:
After we improved the color performance of the 1954/55 RCA 21CT55, we wanted to test it against the 1958 RCA CTC-7 Worthington. The 21CT55 uses a 21AXP22 CRT, testing a “weak” Good on emissions and the CTC-7 uses a rebuilt 21CYP22A CRT, testing a “strong” Good. The 21CT55 uses superior “R-Y-Q” demodulation. The following test images are an effort to visualize the differences in image and color quality between a 1954/55 RCA 21CT55 and the 1958 RCA CTC-7 Worthington. RCA 21CT55 images appear on the left series of photos. Tap any image to open the image carousel, then tap the full resolution image tab. All exposures and focus were set at the center of the CRT image automatically by an iPad Pro 2 10.5. This is not a scientifically controlled test, only an approximation attempt with a non-pro camera. Please excuse the reflections.