1956 Hallicrafters 21CK801M
21" Color Restoration
THE CTC4 HALLICRAFTER CLONE
Like Lazerus Resurrected from the dead
In December of 2008 I acquired what was believed to be a RCA CTC4 Director color set from Bryan Tennyson, in Meridian Mississippi. According to Bryan, he found the set in a leaky back yard shed where it had been deteriorating for about 30 years. It had been subjected to a wet environment and the cabinet was in very bad condition. Initially Bryan was going to restore the set, but he came to the conclusion that it was going to be a bigger undertaking than he wanted to deal with, so Bryan offered the set to me for just the cost of shipping it to Milwaukee. Bryan had the set crated for me, took it to a trucking company and shipped it up to Milwaukee. Many thanks Bryan for your efforts in rescuing this important basket case. The photos below explain it’s condition better than words. This set already had one foot in the grave.
After the set arrived, I sent some photos of it around to some of my fellow TV collector friends and I was informed by Ed Reitan, that what I had was not an RCA CTC4 Director model, but rather a very rare Hallicrafters CTC4 clone, model 21CK801M. And that it was only the second one known to exist (Ed owns the only other known example).
In the early days of color television, RCA had invested many millions of dollars and many years of research and development in bringing compatible color TV to the public. The first 21 inch color TV was the RCA 21CT55; of which about 2000 were produced. The CTC4 series which followed, was the first mass produced 21 inch color TV set series. There were 5 models in the CTC4 series. You can see the 5 models on Ed Reitan’s web site http://novia.net/~ereitan/Gallery/CTC4_Gallery.html Most other television set manufacturers wanted to have color TV sets to sell to their customers too, but it was a very expensive undertaking for the smaller TV manufactures to produce color sets of their own from scratch. So RCA had a program whereby smaller television manufacturers could buy color TV sets from RCA and have the sets branded with their company name. The private labeled cabinets were modified to look different from the genuine RCA color TV models, but the electronics inside the cabinets were identical to the RCA sets. The Hallicrafters company participated in the RCA program to private label this CTC4 “clone” so that the Hallicrafters television dealers could have a color television set to offer to their customers.
As can be seen from the before photos, the condition of this set looked almost hopeless. The cabinet was falling apart, the picture tube had the neck broken off, and the chassis was very rusty. For about 2 years this set sat in a storage room outside of our machine shop. Every time I passed by the set, on my way into the machine shop, I reminded myself that someday I would have to tackle the restoration of this rare and valuable set. But little did I know that it would involve, among many other things, a complete, “FRAME OFF” restoration of the cabinet.
In February of 2011, I finally decided to tackle this massive project. The first step in the restoration process, was the tear down. Little by little, one piece at a time, I removed of all the components from the cabinet. Essentially the set was very complete, except for the missing back. After everything was completely removed from the cabinet, I was able to make a good assessment of the cabinet itself. I was hoping I would be able to save at least the front. But the closer I looked, the more it was apparent that nothing but the frame and some of the solid wood components could be salvaged. The many years of being in a wet environment had caused the glue in every piece of laminated plywood, to let go. All of the plywood was de-laminating. I would have no choice but to rebuild the cabinet from the “frame up”
First next order of business was to try and find veneer core mahogany plywood. As it turns out, most of the cabinet building industry has converted to MDF core (medium density fiberboard) sheet goods, because of the high cost of veneer core plywood. After a long search I located a supplier in the Chicago area that still had some ½” veneer core mahogany plywood. I ordered 2 sheets at a cost of $100/sheet and drove down to Chicago to pick them up. Unfortunately that supplier did not have any ¾” mahogany veneer core plywood, which I needed for the re-construction of the front panel of the cabinet. I was able to locate a supplier in Pennsylvania, and I ordered a 24” x 48” piece and had it shipped to me.
In preparation for the re-construction of the cabinet, I first needed to remove all the delaminated plywood components. That meant that the top, both sides and the front would have to be removed from the frame. The speaker board and the inner cabinet shelf were also badly de-laminated and were also a loss. And when I got all the panels removed, I discovered that the frame also had some issues. Some of the frame components were badly warped, and needed to be replicated. Many of the joints were lose or broken. All in all I spent 2 days just repairing and replacing frame components. This cabinet has two wooden legs that run from front to back. The originals legs were badly trashed, so I also had to re-construct two new leg supports from solid mahogany as shown in the photo below.
Now that I had the materials, and a restored frame, I could start the re-build. I was able to use the old delaminated panels as patterns for drilling holes in the new panels.
First panel to be reconstructed was the inside bottom shelf. This was replicated from ½” birch plywood that I got at Menards. I used the old shelf as a pattern and simply duplicated it. All the radius’s and holes were drilled using Forstner bits. The completed shelf was glued and screwed onto the restored skeleton frame.
Upon close examination of the old bottom shelf I noticed that there was a number 2 was stamped into the plywood near the left rear corner. It was customary to number the early production cabinets. So I guess this is probably the second Hallicrafter CTC4 clone cabinet made. I used a utility knife and removed a 2” square piece of veneer from the old plywood shelf containing the #2, and transplanted the #2 onto the new shelf in the exact same place it was on the original shelf. I also saved the original paper serial number of the set, which was stapled to the left rear frame member. It was later re-stapled to the frame where it was originally located. Pasted to the inside of the right cabinet side panel, is a tube placement chart and another label. Those labels were scanned, reprinted, and later re-attached to the inside of the finished cabinet where they were originally located.
The next order of business was to replicate the front panel, from the ¾” mahogany ply. The front consists of 4 pieces. There are many special rabbits, miters, and other tongue and groove features on these pieces. On top of that; every piece has to be edge bound with a mahogany veneer in order to hide the plywood core from showing. All of the joints are also drilled and dowelled for strength. I made my own doweling jig on the milling machine from a solid billet of aluminum. This custom doweling jig allowed me to do a custom spacing of the dowel holes to maximize the joint strength. When the front was complete, it was attached to the already repaired skeleton frame.
With the most complex items finished, it was on to making the cabinet sides. Making the sides was very straight forward. All that was needed, was to cut the ½” mahogany plywood to the exact size required, and bind the edges with mahogany veneer and trim. The finished panels were then attached, one at a time, to the frame with glue, clamps and screws.
At this point about 2 weeks of work had gone into the cabinet restoration, and all that was left to re-construct was a new top panel. Once again a simple matter of cutting the ½” mahogany plywood to size, and binding the edges with mahogany veneer. However there were a number of solid wood attachments that needed to be transplanted from the old top to the new one. As might be expected, some of those old components were too badly warped to salvage, and so they had to be cloned from new material. I used Poplar because of its good stability and strength.
I also needed to fabricate a new speaker board, because the old one was delaminated just like all the rest of the old plywood. Using the old speaker board as a template, I fabricated a new speaker board from ½ inch plywood. Fortunately the old grill cloth was reusable. I cleaned the grill cloth and re-attached it to the new speaker board using 3M #77 spray adhesive and staples. The speaker cone on one of the speakers was completely eaten away by mice, but I replaced it with an identical replacement from a CTC5 TV set that I had parted out some time back.
The cabinet re-construction was now complete. It just needed to be stained and clear coated. I farmed out the finishing work to a fellow that I know. He has refinished some other sets for me and he does a nice job. The only problem is that he is very slow. It usually takes several months to have a cabinet re-finished, but I hate cabinet finishing so much now that I gladly endure the long lead time and cost, in order to avoid having to do it myself.
PHASE TWO….CHASSIS RESTORATION…….
As one might expect, the chassis was in almost as bad a condition as the cabinet. There was a fair amount of rust, but the main chassis itself, was mostly rust free. The cover over the If circuit board and all of the high voltage cage panels were badly rusted. So I removed those parts and had them stripped and re-plated with a nice shiny coating of tin. Actually I had the parts zinc plated on the first attempt, but the zinc looked much different than the original cadmium plating on the chassis. I so I had the plating shop strip the zinc off and re-plate the parts in tin. The tin looks pretty much like cadmium plate.
An initial inspection of the chassis underside revealed that the set must have had a fire at some point. It looks like the power supply choke burned up and caused a lot of damage in that vicinity. A number of wires had been replaced, the jumper circuit for measuring the cathode current of the horizontal output tube, had been disabled, and there were numerous 2 watt power resistors that were toasted. The plastic insulation on some wires was melted, and the set had generally been subjected to very poor repair shop workmanship. If you look closely at the area surrounding the power supply choke (above and to the left of the power transformer) you will see that the underside of the chassis is stained brown from the smoke created by the choke that burnt up.
My first task was to remove the tuner assembly. The cover on the VHF tuner was badly rusted. I had a spare tuner cover from a CTC5 tuner that was in nice shape so I changed it out. The tuner action was very bad. It needed much cleaning and lubrication; especially the cam mechanism which operates the UHF/VHF antenna switch. A simple application of some contact cleaner/lube and some lithium grease on the mechanical cam got the tuner action back to good as new again.
Prior to starting the re-cap, I decided to check all the peaking coils, and inter-stage transformers for any that may be open. I found one peaking coil that was open. I also found several inter-stage transformers that had been used by mud dauber wasps to make nests. The wasps filled the holes in the tuning slugs with mud and then the wasps live inside. I was able to use a pointed tool to remove the mud and compressed air to blow the dust out. A couple drops of WD40 inside the coils allowed me to free up the cores so they turned smoothly again.
When I removed the HV cage I noticed that mud dauber wasps had also made a nest in the HV choke next to the flyback . Sorry wasp, your house is history.
The next several days were spent on replacing paper capacitors, checking and replacing resistors, and replacing damaged wires which had melted insulation from the fire. I found many resistors that were way off value, and a number of capacitors that were either replaced with the wrong value, or had voltage ratings that were too low.
During this phase of the restoration, I referred to both the Sams Photofact prints and the original RCA service bulletin to carefully check component values and to check the wiring. In the RCA service bulletin, there are many production changes listed. I am keeping the chassis as wired when I received it. Where the chassis does not agree with the RCA print, I refer to the change list to make sure the difference is based on an RCA factory authorized wiring change. The Sams schematic is likely some version of the CTC4A. The chassis I am rebuilding is a CTC4A but it more closely resembles the RCA schematic.
The 100 ohm vertical centering pot located on the flyback board was toast, and so was the focus pot. So I replaced them but the originals have extra long shafts and I could not locate any exact replacements with long shafts. So I machined some ¼” shaft couplers, and machined a flatted extension shaft from ¼” brass stock, to make the original shafts longer.
The last phase of the chassis restoration was to re-stuff the electrolytic cans. I did not have all the correct values in stock so I placed an order for more parts. I was able to get some hard to find values on Ebay. Two of the cans are 200MFD single section. I got lucky and found some single section snap-in electrolytics that were 200MFD 350vdc and fit easily into the old can body. I bought a bunch of these 200MFD for stock, because I will be restoring two other CTC4’s at some point.
I have been asked by several collectors to demonstrate my can re-stuffing methodology. So rather than post a bunch of photos and a lengthy explanation on this page, I will refer you to the “My Methods” pages where I will eventually have a web page on how to re-stuff electrolytic cans.
I also disabled the original selenium stack rectifiers. I replaced old seleniums with 1 amp 1000piv silicon diodes for added reliablilty. Doing this causes an increase in B+ voltage from about 350 volts to around 415 volts due to the higher efficiency of the silicon diodes. In order to bring the B+ back down to around 390 volts, I added a 10 ohm 25 watt power resistor in the AC side of the power supply, in series between the common leg of the diodes, and the 4.5 amp power supply fuse. I left the original silicon stack rectifiers on the chassis for appearance sake.
At this point I was ready to hook the chassis to my 21AXP22 test jig, and see how the set performed. After much fiddling and tweaking of adjustments I was able to get sound and a picture of sorts. I decided not to attempt any convergence at this point because I would only have to do it again when I placed the chassis into the restored cabinet with the CRT components it was going to be mated permanently with.
By now the cabinet refinisher had completed the cabinet and it was back in my possession. He did an incredible job on the finish. Now it was time to install the rest of the cabinet components. I re-attached the protective ventilation screen under the chassis shelf, and installed the perforated metal shield that faces the chassis bottom. I installed the CRT bezel, the 21AXP22 CRT, the CRT shroud, and purity magnet ring. During the cabinet restoration, I polished the brass trim that goes around the safety glass, and coated it with 2 coats of clear lacquer. At this point I installed the safety glass and the refinished brass trim. Then I installed the deflection yoke.
IN the photo below, you will see the installed crt support structure. You will note that the coating on the polyethylene crt shroud is now sort of a light biege color. After some experimenting, I found that Tarn-X silver cleaner, which you can buy at the hardware store, removes the black coating. All you do is soak a small sponge with the Tarn-X and sort of wash the surface of the crt shroud. This is a job that you will want to do outside, because Tarn-X stinks something owfull. As it turns out, the coating on the crt shroud is actually metalic SILVER, and the black coating is silver oxide.
It is typical for the covers on many early RCA color deflection yokes to disintegrate. These covers are made of an early plastic called CAB (cellulose acetate butyrate) which is very prone to decomposition. A few years ago I devised a method to make replacement deflection yoke covers from black sheet styrene which I obtain at the model train store. If you go to the “My Methods” section of this web site you will find a web page that describes the procedure I use to replicate deflection yoke covers. And at this point I installed the replicated speaker board to which I had already re-attached the original grill cloth from the old speaker board.
Now it was time to install the restored chassis. I hooked everything up, turned the set on, and started making adjustments. I started with the usual focus and purity adjustment and screen and background adjustments. Then linearity adjustments, and horizontal and vertical centering. When I was satisfied with the general geometry and purity, I made some preliminary video adjustments; AGC, contrast, brightness tuning etc. I had a rather mediocre picture at this point. It still needed a lot of tweaking to get it to where I would be happy with it.
But in order to do final video adjustments, I still needed to do convergence adjustments. So I started doing static and dynamic convergence, when I made the discovery that the convergence circuitry was highly dysfunctional. I couldn’t get the dynamic convergence controls to work anything like they should. I actually had better convergence with the convergence yoke unplugged. After about an hour of failed efforts, I gave up. I removed the chassis and took it back downstairs to my basement electronics lab to see if I could determine what the problem was. It wasn’t long before I discovered that almost every control pot on the convergence panel was defective. Evidently, 30 years of sitting in the wet shed, getting rained upon, took a heavy toll on all the control pots. All these pots would need to be replaced.
I made a list of all the parts I was going to need and got on line to order new pots. The amplitude and background pots were readily available. But the screen pots were a bit more difficult. The screen pots ride at “boost” voltage of about 850 volts DC. Most pots are only rated for a maximum of 600 VDC, and because of this RCA devised a scheme to insulate the pots from the chassis. In addition these pots have a plastic shaft to prevent shocks to the service technician. Pots of this exact type were not available. I would need to do some surgery and transplant new resistance elements from donor pots onto the old screen pot bodies. I was able to find some donor pots in my pile of spares and I transplanted the resistance elements from the donors to the original pot bodies.
But I wasn’t done yet. There are 3, dual concentric 100 ohm pots, that control vertical tilt and amplitude. These pots are pure “unobtanium” They were probably special ordered by RCA just for the CTC4 series chassis. This was not an off the shelf stock part that any electronic parts wholesaler would have on the shelf. So I started a long search for anything that might be suitable. After running into a dead end for several days I discovered that Surplus Sales of Nebraska had some pots that were almost what I needed. They had some dual concentric pots that were 100 ohm / 200 ohm. They were a bit pricy at $15 each, but I needed them and when you need it you buy it. I purchased all that they had, 13 pieces. I figured that I would take the pots apart and use all the 100 ohm resistance elements to make a total of 6 100/100 ohm dual concentric pots. I had more CTC4 chassis that might need this part in the future, so I was planning ahead. A few days later I discovered a source for more 100 ohm resistance elements of the correct type and in the end I was able to build 13 of these dual 100 ohm pots for future use.
After all the new control pots had arrived I completely rebuilt the entire convergence panel with all new components. Working on the convergence panel is quite difficult. There are dozens of wires leading from all the lugs of the controls to other points inside the convergence panel. There's also a 6 pin connector that is difficult to get at because all this stuff is burried deep inside the control panel chassis. The best course of action is to completely dismantle the entire chassis, install all the new pots and then rewire everything in a sequence that permits you to get to the terminals easily. There are a total of 14 pots sections, 3 chokes, 3 capacitors, and a 6 pin connector to wire.
My good friend John Folsom was due to fly into Milwaukee for a 10 day visit. So I took a break from the project and left the chassis for more expert hands. I figured I would let John try his hand at alignment to see if we could improve the picture before installing the chassis back into the cabinet. When John arrived we set up the alignment equipment and John and I followed the IF alignment instructions in the Sams Photofact. Unfortunately we had some sort of problem that we could not trace down. The waveform on the scope was not what we expected to see. And when we were finished with the alignment procedure the picture on the screen was total crap. We never did resolve that issue, but through trial and error we were able to get the alignment to where we obtained a fairly decent picture. So we hauled the chassis back upstairs and reinstalled it in the cabinet.
We hooked up all the connections and turned the set back on. At this point I resumed where I had left off several weeks before with my first failed attempt at convergence. This time I was delighted to find that all the new convergence controls were working exactly like they were supposed to and I was able to converge a pretty nice cross hatch pattern on the screen.
At this point I hooked up a DVD player to see what a live signal looked like. It wasn’t too bad. I had good contrast, brightness, focus, picture fidelity, and color balance. However there was a bad problem with audio noise in the picture, especially in saturated color areas. At this point the project was put on hold because my brother was gravely ill with a brain tumor. I came back to this project about 6 months later and started where I had left off, and this time I was able to fine tune the noise traps so the audio and color noise were eliminated. The only problem that was left was a ghost in the picture that I can’t seem to eliminate. But considering what this set has been through, I am very happy with the quality of the picture.
There were only a couple things left to do to complete the restoration. Early on, Ed Reitan took some photos of his Hallicrafters CTC4 clone for me. Of special interest was the original Hallicrafters decal on the front of the set. My set was so badly deteriorated when I received it, that it no longer had the decal present. Using a good photograph that Ed Reitan supplied, I was able to use Microsoft Publisher to re-create new art work that replicated the Hallicrafters logo in the photograph that Ed had sent me. I emailed the file off to a company that specializes in producing water slide decals. Using my art work file, the company made water slide decals that I was able to apply to the restored cabinet.
The set was also missing the original back. Fortunately I had a fairly nice original back on another RCA CTC4 set. I took the RCA back to a local company that makes custom displays for the advertising industry. This company has a very large CNC router with a 5 foot by 10 foot bed. They took the original RCA CTC4 back that I provided and programmed their CNC router to make an exact duplicate of the RCA back that I brought them. The original CTC4 backs have one of the common cardboard bump-outs for the picture tube neck. So I needed to come up with something to replicate the missing bump-out. I decided to use .080” sheet styrene that I also use for replicating deflection yoke covers. I painted the finished bump-out with brown enamel spray paint. Here are a couple photos of the finished back and the bump-out installed on the completed project.
So here it is, like a phoenix rising from the ashes, THE "LAZERUS" CTC4 HALLICRAFTER CLONE in all its glory.
And here is some original 1956 advertising literature for the set, courtesy of Ed Reitan.