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RCA CTC-5 Deluxe Chandler Restoration
Here is a link to the progress thus far.
https://visions4netjournal.com/vinta...-tv-page-twoa/ I wonder who the gentleman from California was? |
I like the CTC5 Deluxe. Next to the the CT100 and 21CT5, it was the last RCA Color TV with more than 500kHz chroma bandwidth for many years. It has two stages of audio IF for better quality sound. It misses the simplicity of B&W setup and convergence of later sets but it can be a good performer.
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Light that sucker up right now, see what it does as is...... Maybe there's still an old Ed Sullivan Show stuck in the tubes & needs to get out.... . |
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I recall a 1955 issue of the RCA Review I read decades ago, long before I had a chance to examine the CTC5 chassis. I recall they did a study allowing a degree of quadrature crosstalk and I wonder if the Deluxe chassis was an attempt to justify the addition chroma resolution at the expense of the crosstalk? Interestingly, subsequent RCA sets stuck with the 500kHz chroma response. |
Thanks.
If i recall correctly, much later Zenith solid state sets used a simplified color bandpass that consisted mainly of a compensation circuit for the IF rolloff, with a not very sharp lower edge cutoff that allowed decent color resolution with some quadrature distortion. Designs that try too hard to get max bandwidth with no quadrature distortion will suffer from ringing chroma transients, which can get worse than the quadrature crosstalk if the cutoff is really sharp. |
By the way, if the response is significant in the lower chroma sideband, I would expect the DeLuxe to have more cross-color than subsequent sets.
Once it's restored, it would be interesting to compare the effect in the Indianhead resolution wedge to a Super or a later RCA. Come to think of it, I've never looked at this in a CT-100 - would be interesting. |
May 6, 2024, day one.
Restoration begins. Mike Doyle came by today to pick up the CTC-5 chassis and take it to his shop. He will jig the chassis to a test color CRT. He needs to finish a Korean prewar radio and after, will restore his own personal CTC-5. After that he will start on my CTC-5, the subject of this post. Mike has restored two other CTC-5’s prior to this project and is familiar with the circuit design and layout. Below, a few pictures of the disassembly. Photo #1 RCA added printed circuits with this model and looks to be original. Photo #4 6X8 tube missing from tuner assembly. Photo #6 RCA Monogram factory rebuilt 21AXP22, serial # CC11949. Photo #7 Emissions test of CTC5U chassis. Photo #8 All three guns test very good. Photo #9 Life test reduces filament voltage by 10% and no change in very good to excellent readings. https://visions4netjournal.com/wp-co.../IMG_3777.jpeg https://visions4netjournal.com/wp-co.../IMG_3778.jpeg https://visions4netjournal.com/wp-co.../IMG_3780.jpeg https://visions4netjournal.com/wp-co.../IMG_3774.jpeg https://visions4netjournal.com/wp-co.../IMG_3781.jpeg https://visions4netjournal.com/wp-co.../IMG_3773.jpeg https://visions4netjournal.com/wp-co.../IMG_3766.jpeg https://visions4netjournal.com/wp-co.../IMG_3765.jpeg https://visions4netjournal.com/wp-co.../IMG_3767.jpeg This link will take you to my website page. https://visions4netjournal.com/vinta...-tv-page-twoa/ |
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May 24, 2024 Today, we moved the CTC-5 cabinet and CRT into our home theater room, awaiting the restored chassis from Mike. I do not plan on restoring the cabinet. It’s in remarkable condition with only a few nicks and fingernail damage around the channel selector. Full res, https://visions4netjournal.com/wp-co.../IMG_4739.jpeg |
My CTC5N chassis Whitby is almost identical to yours. In mine I am beginning to see the defocussed silvering highlights the CRT and it appears the CRT has had its day. Certainly under test, the gun emissions are not balanced and Red is dropping off. I am weighing the merits of using a "Britener" to boost the filament voltage.
I tried testing the tube with increased filament voltage and emission picked up on Red. But the guns do not appear to track well. I would be curious to hear experiences with others aging CRT performance. |
We have not been able to achieve the same level of color fidelity as the Westinghouse H840CK15 with our RCA 21CT55. Our CTC-7 has a brighter more saturated image, but not as accurate as the H840CK15. I’ve never seen a live CTC-5 image, only in photos. It should be interesting if nothing catastrophic is found in this restoration.
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off my own DVD/Blonder-Tongue. Its abysmal due to bad RF/IF tuning. But on my own test patterns with only large color areas the colors are just fine. I was unable to attend this year's convention where I was going to align it. Next year. |
July 25, 2024
It’s on the bench. The “official” start of restoration begins. From Mike, It is on the bench. I will be connecting crt wires back to where they need to be and I will install the volume/on/off brightness control with a new switch unit. I will install missing tubes and fire it up to see “what we have got” for the beginning of restoration. Here we gooooooo!!! Mike https://visions4netjournal.com/wp-co.../DSC03101.jpeg https://visions4netjournal.com/wp-co.../DSC03102.jpeg |
July 28, 2024 Day 84
Volume/Brightness control rebuild From Mike, The chassis came to me with no brightness/volume/switch control.# That part was a bunch of broken pieces.# I had a control assembly in my parts pile, but in checking it out, the switch was bad and the 1 megohm volume control pot was "open circuit"# The part number for this piece is RCA 102156 which, as far as I can tell is un-obtainable.# If this chassis is going to work again, the control that I have here would need to be re-built.# A very delicate operation.# The problem was the brass rivets that contact the wire lugs to the carbon path of the pot were loose.# So, I had to try something that I have never tried before, and apparently, it worked. Pix 1# Volume/Brightness/switch loose wires and damaged parts from the original assembly. Pix. 2,3,4 My control with issues like open 1 meg volume control and bad switch. Pix.# 5# Pieces retrieved from broken assembly.# These had some usable parts that I used in the re-build process. Pix. 6 Disassembled for repair. Pix 7. I started by drilling with a pin vise by hand to remove the brass rivets, but the rivet started rotating so I switched the tooling to Dremel tools. This worked well. Pix. 8. The repair is a success showing the 1 Meg reading on the ohm meter. Pix. 9,10.# Details of the #2/56 screws that replaced the rivets that I removed. Pix. 11.# Control re-assembled and ready to install including the new switch unit. Next, is to install this unit and then figure out the connections for the crt wires and get them hooked up.# Then, it is time to fire it up and see what we have got. Cheers,# Mike https://visions4netjournal.com/wp-co...SC03102-1.jpeg https://visions4netjournal.com/wp-co.../DSC03103.jpeg https://visions4netjournal.com/wp-co.../DSC03104.jpeg https://visions4netjournal.com/wp-co.../DSC03105.jpeg https://visions4netjournal.com/wp-co.../DSC03106.jpeg https://visions4netjournal.com/wp-co.../DSC03107.jpeg https://visions4netjournal.com/wp-co.../DSC03108.jpeg https://visions4netjournal.com/wp-co.../DSC03113.jpeg https://visions4netjournal.com/wp-co.../DSC03115.jpeg https://visions4netjournal.com/wp-co.../DSC03116.jpeg https://visions4netjournal.com/wp-co.../DSC03117.jpeg Stay Tuned. |
NEXT
The crt wires have been reconnected to the proper points. No tubes have been tested and several of the tubes are missing. I will install missing tubes tomorrow and hook up to the jig. It is time to "see what we have got" before any further restoration procedures. The next 4 pictures are as follows. Pix 1 Chassis top view before preliminary cleaning with vacuum and brush. Pix 2 Chassis after vacuum and brush cleaning. More cleaning will take place as the restoration continues. Pix. 3 and 4. The newly rebuilt control mounted and wired. More to follow. Mike https://visions4netjournal.com/wp-co.../DSC03119.jpeg https://visions4netjournal.com/wp-co.../DSC03120.jpeg https://visions4netjournal.com/wp-co.../DSC03121.jpeg https://visions4netjournal.com/wp-co.../DSC03122.jpeg |
July 30, 2024 Day 86
From Mike: Approx 7-29-24. I jigged the chassis to my 21FBP22 today, connected to a variac for first power up. When I got to full voltage, nothing was alive in the power supply. The D.C. voltages should be 385v,,,, 275v… and 140v. (roughly). All filaments were lit to normal brightness except for the 5U4 Recifier tubes, which were both blown. NO continuity through the filaments. This usually means that they died from an overload somewhere in the power supplies. I checked for shorts to ground, but nothing obvious. I then checked the fuse in the 385 volt line only to find that it was OK. BUT, somebody thought that it was an OK thing to install a 3.5 amp fuse into a place where it there should be a 2 amp fuse. Some technicians seem to think that it is an intelligent thing to do that. Upon replacing the two 5U4 tubes from my “good used” pile, and replacing the fuse with the proper value, I tried again only this time I monitored the D.C. amps inline with the fuse upon power up. It got to just under 2 amps when the fuse blew. The D.C. 385 volt supply never got over 50 volts with the variac at about 75% which would be around 80 VAC line volts. Still no obvious shorts using an ohm meter, which means that the short is only there with voltage applied. It is time to start changing all the electrolytic capacitors in all sections of the power supply. There are 4 “cans” on the chassis, and all of them are in the front where the crt insulator boot can interfere with the 2 in the front, if the cans are too tall. I learned this one the hard way a number of years ago when I restored my set. The best way to fix this problem for maximum reliability is to re-locate the caps with individual units under the chassis, and leave the cans in place for cosmetic purposes. Fortunately, there is a lot of room to work with under the chassis to accomplish this task. I cut out the studs on the cans one at a time for further clues with the ohm meter. What I found was that several of them were leaking voltages from section to section, rather than the normal failure mode of stud to ground. This did offer some explanation to the overcurrent condition with voltage applied. I spent a lot of time over the next few days mounting tie points for the new capacitors. Pictures 1 through 4 are the newly mounted electrolytic capacitors and some others that I replaced since I was already working there where the new ones were mounted. Upon the next power up, I had 325 volts of D.C. on the main output of the rectifiers. Some success! It will likely be much more like 385 later when I install NEW 5u4 rectifiers, but this voltage is fine for now during more troubleshooting. I now have weak audio but NO high voltage at all. A quick check of the Horizontal output and damper tube showed that they are probably OK. So, a quick check for a Horizontal Oscillator drive signal on the control grid of the output tube showed NO signal there. The oscillator tube checks ok but I tried a new one anyway. No change. I then checked for B+ at the osc. stage and that looked OK. Then I got lucky when I did a careful physical exam on the osc. board. I was prompted to do this since I noticed that some tech ahead of me mounted new capacitors on top of the board. That is not a good thing to do because it often times weakens the solder connection on the bottom side. That is when I found the capacitor that is across the oscillator coil had a cold solder joint. These oscillators work much better when the coil and capacitor are actually connected to the circuit. (sarcasm) . Picture 5 The red pen shows the point of cold solder joint. Picture 6 The previous techs “handy work” on top of the board. (sarcasm) Picture 7 Signal now present at the grid of the H. Output tube. But, still no high voltage even after I changed the 3A3 HV rectifier and the 6BK4 Regulator. Further troubleshooting continues. Cheers, Mike Authors note: Spoiler, we do have HV! Description to follow. https://visions4netjournal.com/wp-co.../E-caps-1.jpeg https://visions4netjournal.com/wp-co.../E-caps-2.jpeg https://visions4netjournal.com/wp-co.../E-caps-3.jpeg https://visions4netjournal.com/wp-co.../E-caps-4.jpeg https://visions4netjournal.com/wp-co...onnection.jpeg https://visions4netjournal.com/wp-co...ed-on-top.jpeg https://visions4netjournal.com/wp-co...ve-Signal.jpeg Visions4 Magazine https://visions4netjournal.com/ |
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Hi to all,
Hi etype2, Very well documented restoration description by a master of the art. You're so lucky to have someone local able to do this. Just curious, what brand HV electrolytic capacitors does Mike use? (photo of a sample below) Best Regards jhalphen Paris/France |
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All I know is he mentioned “high quality”. |
Did you not prepare the electrolytics before powering up?
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We have HV and a raster, more to follow.
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August 7, 2024 Day 94
OK, I really do have High Voltage! My H.V. meter that has been very reliable for over 40 years lied to me! As I moved the schematic to a different part of the bench, I noticed the hair on my arm standing up when close to the CRT face. I swapped out the H.V. probe and it measured 16 KV. So, that is not enough, but good for now!! Pix 1 First image on this set for likely many years shows no sync, or maybe AGC issues. Hard to say. But I am going after the Horizontal Osc. board next. Pix 2 Parts removed. I replaced every part on this board except for the coil, which is obviously OK. All caps are new. Some resistors looked tired so they got replaced good or bad. Pix 3 Rebuilt Horizontal Osc. board. Pix 4. First good image with color. I still suspect maybe there is an AGC intermittent, but this is a milestone in the restoration process since it tells me a lot about the rest of the set. https://visions4netjournal.com/wp-co...3-no-sync.jpeg https://visions4netjournal.com/wp-co...sc.-board.jpeg https://visions4netjournal.com/wp-co...Rebuilt-2.jpeg https://visions4netjournal.com/wp-co...ood-image.jpeg There is still a lot of work to be done. I installed 2 brand new 5U4 tubes and the power supply voltages are now what they should be. I have tested all of the tubes and found several weak ones and they have been replaced. There are a number of controls that have issues and I am not sure if cleaning them will help. Most of them have to do with convergence. I may be facing some rebuilding of controls like I did with the volume/brightness/switch unit. Time will tell. Next, I plan on going after the Sync/AGC/Sound I.F. section. Even though the High Voltage is low, I am not too concerned with that for now. It should be 22KV. Onward, Mike |
One thing to be aware of on these CTC-5s is that fixed bias HV regulation wasn't a great idea...On both of my CTC-5s I added a HV regulation control pot. It's pretty straightforward if you compare the CTC-7 and CTC-5 HV reg circuit schematics. The CTC-7 deletes one resistor and replaces it with a pot and a fixed resistor IIRC. The ability to adjust HV regulation helps with HV level in these sets.
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There have been a number of discussions in this forum on the CTC5 and it's inability to muster enough high voltage. I found mine barely able to squeek the 21kV. I would manage to make the 21kV when there was no beam current (black screen). But soon as the brightness would go up, the HV would dip a bit..
I didn't bother with the HV pot modification as the 6BK4 would start to draw current when the HV reached close enough to 21kV. What I did do was to ensure I had fresh good horizontal output and oscillator tubes and ensure there was sufficient horizontal drive to the output tube grid. I also substituted (and this was crucial) a solid state 3A3 rectifier for the original tube 3A3. The solid state version is a direct plug in replacement and changing it eliminated the HV sag with increased brightness. The 6BK4 now is doing its job properly as a shunt regulator. |
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Those solid state 3A3s are my go to on sets where all parts check good or are new and I can't get the horizontal output cathode current low enough to be happy. They can help out with HV, but when the only way a set will top 18KV is with the regulator unplugged the pot becomes the necessary option. |
It's been a while since I messed with my CTC5, but I remember getting about 23-25 KV with a dark screen, and about 19-20 KV before the HV would fall off a cliff and go low enough to lose focus and brightness. This was with stock circuitry and using tube focus and HV rectifiers. Might as well remove the 6BK4 since all it seems to do is set an upper HV limit with zero beam current. I haven't tried solid state diodes myself yet.
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If you have such a large variation of HV in a regulator type set, something needs to be fixed. Working properly, the HV should be constant with varying brightness until you turn the brightness (beam current) excessively high, the regulator stops drawing any current, the HV starts dropping below the regulated value, and the picture goes out of focus and the width and height start increasing.
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The CTC5 high voltage is supposed to be 21 kV. The shunt regulator is supposed to be holding the voltage at 21kV so if it is going above 21kV, something is amiss with the regulator circuit.
On the other hand if it is stuck at 18kV and you are sure of your meter calibration, again something appears to have drifted in the regulator circuit. I'd disconnect the 6BK4 plate and the measure the high voltage. If it reaches about 24kV with a brightness turned right down, that would be correct. |
My 5, although basically working, could probably use a wholesale replacement of the carbon resistors, since I've already had so many of them that were either off value when I started, or have gone bad over time and caused new problems. My HV probe is a Fluke, and the kind used with an external DMM, and seems to be accurate. The big issue is how the HV just drops off suddenly if the brightness control is advanced too far, and, according to others here on this board, is a normal characteristic of the CTC5. In any case, IMO, the 5 really isn't a good "daily driver" because of the weak HV supply and the fact it just isn't very bright with the original AXP tube, not to mention convergence drift with the DC static adjustments instead of the magnets everything else used.
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The HV drooping issue was a concern which was mainly addressed by selecting a new horizontal output tube and replacing the vacuum tube HV rectifier with a solid state replacement. Two issues I see is the dimness of the 21AXP22 which is overcome watching the set in a darkened room. The other is poorish black level clamping which I feel may have been exacerbated by the contrast control modification.However I do not see it any worse than subsequent chassis's CTC7, CTC9 etc. |
Regarding poor DC coupling, I am torn between keeping it authentic or making it better than original. So far I have come down on the original side, a good part because I'm lazy. :D
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I did put in the CTC-7 circuit change, my excuse being that was something actually being done to sets in the field. No sets had 100% DC coupling after the CTC-5 until some point when it was done in transistor sets. Consumer Reports complained about it every year.
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Some progress.
After a Summer break from the hot Arizona heat, restoration resumes. September 20, 2024, Day 138 From Mike. I am slowly changing parts on the Sound, AGC, Sync printed board. I have found a number of questionable solder connections along the way on this board. It has forced me to change every single component except for the transformers which are typically not problematic. Somebody missed "solder skills day" in the process of manufacturing. I think this set was very problematic from the day it left the factory. Obvious bad solder joints with component pins easily seen moving when exercised from the top of the board. Also, I found some notes in my CTC5 "red line" drawings that reminded me of a mod that I made on my set in the High Voltage Regulator. I added a HV control. I will be doing that mod on this set. It entails removing a control on the back panel that never did anything. It is called the Matrix Balance control. It is supposed to control current in the "X" and "Z" demodulator tubes by way of adjusting cathode current. This is the only RCA color chassis that ever implemented that control and it was eliminated. All sets after CTC5 used a fixed cathode resistor, which is the best way to go. I will replace that control with a 10 Megohm pot and a resistor divider in the HV regulator tube circuit to allow for HV adjustments. More to come. Cheers, Mike |
September 25, 2024
Update for AGC, Sync, Audio rebuild The printed board that controls AGC, some of the Sync and all of the Audio has been completely rebuilt. I replaced all of the components on this board, not just the capacitors. I found some resistors out of tolerance and a number of cold, poor solder joints throughout. This board was no doubt causing multiple intermittent problems for many years, one of which I experienced earlier in this restoration. There was a horizontal sync problem that mysteriously went away. I decided to do a complete component replacement as opposed to looking for intermittent solder connections and/or faulty components. The CTC5 had numerous issues with AGC and most of that is due to the fact that the engineers thought that it was a good idea to create the 140 VDC power source from the cathode of the audio output tube. VERY BAD design to mix any two circuits that way. I do not know why they did not just add a 20 watt resistor to the existing 285 volt supply which would have been a better design. It would have been a very robust design compared to making the audio output tube do the work of making the 140 volt supply which caused many problems that were difficult to troubleshoot. Pix 1 Board before restoration. Pix 2 Board after all components changed. Next, I go to the High Voltage Regulator and make a mod to allow control of the High Voltage setting. Cheers, Mike https://visions4netjournal.com/wp-co.../DSC03185.jpeg https://visions4netjournal.com/wp-co.../DSC03191.jpeg |
Hi to all,
Hi Etype2, Following this restoration's progress with interest. Will you use the CTC-5 through it's RF tuner or add a video input for better resolution? An idea of when it will be completed... Best Regards jhalphen Paris/France |
Hi Jerome,
Mike did not make that modification for our previous restorations, so I doubt it will happen on this set. Is there a visible improvement by doing this? I’m in the camp for leaving it stock. Completion, possibly by the end of this year? |
Hi to all,
Hi Etype2, Video input mod will not yield "spectacular" resolution increase except if the tuner and especially the IF chain has drifted badly out of optimum bandpass. I suppose your Golden Restorer will do a full RF/IF sweep on your set. As a personal experience, on my CT-100 i purchased Pete Deksnis's video input kit - derived from RCA's studio monitor mod (about 20 years ago). The seller of my CT-100 warned me that the TV was not performing very well on upper VHF (Band III) channels. As the CT-100 requires IF alignment of no less than 5 IF stages, i chickened out. It is one of the most difficult sets to align and you need a full Lab of gear to do it. The CT-100 video input module works well, but as you know from your Westinghouse, the 12" picture of a 15GP22 is nothing to brag about resolution-wise. Oh well, it's IN COLOR ! (1954). Best Regards jhalphen Paris/France |
Jerome,
Mike will do a full alignment. Is your CT100 working? |
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