1955 RCA 21CT55 21" Color Restoration

Sometime around 2008 I met a fellow Milwaukee TV collector by the name of Colin Wood.  Colin invited me over to see his collection and in the process I discovered he had this 1955 RCA 21CT55 color set in his collection.  As the story goes, Colin told me that he was on a job site doing some HVAC work and he discovered this set in the attic of the home he was working in.  Colin asked the occupant what they knew about the set and they told him it had been in the attic since they moved in and was left by the previous occupant.  Colin inquired if he could have the set and they told him he could have it free for the taking.  A prime example of being in the right place at the right time!  In any event I told Colin that if he ever wanted to part with the set to please give me the first chance to purchase it.  Sometime later I got a call from Colin and he offered to sell me the set.  I accepted the offer and that is how the set came into my possession.  We don’t know where the set originally came from or who it belonged to.

The set was in fair condition when I received it.  The cabinet was structurally soundbut the finish left a lot to be desired.  The set had the “original” 21AXP22 picture tube which the set left the factory with.  However the picture tube was extremely weak and was not usable.  Two of the metal panels on the high voltage cage were missing and so was the metal back of the set.  But the chassis was totally free from rust and it appeared that the set was in fairly good restorable condition.

The first order of business was to have the original 21AXP22 picture tube rebuilt.  I made a trip to Hawkeye Picture Tube in Des Moines, IA  and had Scott Avitt rebuild the tube for me.  The tube came through the rebuilding process with flying colors and once again the old picture tube tested like new.  This photo shows Scott Avitt installing the new electron gun assembly during the rebuilding process.

As I mentioned earlier there were some panels missing from the high voltage cage.  These needed to be replicated.  As luck would have it, one of my other collector friends, Steve Kissinger, also has a 21CT55 and he was making a trip to Wisconsin to see his mother who lives close by in a neighboring town.  Steve graciously removed the panels off of his set, which I was missing and brought them to Milwaukee on his trip.  I was able to make some paper patterns from Steve’s parts, and I later used the patterns to make new panels out of 24 gauge galvanized sheet metal.  The two new parts can be seen in this photo of the chassis.  You will notice that the design of this High Voltage cage is very poor.  The side panels are solid sheet metal and have no ventilation holes.  This design does not allow for good ventilation, which in turn causes overheating of the horizontal output transformer. 

The next step was to restore the chassis.  The chassis of the 21CT55 is a modified version of the chassis that is used in the 1954 RCA CT100 15 inch color TV set.  The chassis is modified for the 21CT55 to provide dynamic convergence and a beefed up high voltage section to drive a 21 inch picture tube.  Restoration of the chassis was fairly straight forward.  I replaced all the wax paper capacitors, checked and replaced any out of tolerance resistors, and re-stuffed all the electrolytic capacitors. This chassis uses a pair of old style selenium stack rectifiers in the B+ power supply. These old stack rectifiers are prone to failure and are inefficient, so they were replaced by a pair of 1 amp 1000 PIV silicon diodes. Because the new diodes are more efficient and cause a boost in the B+ voltage, I added a 7.5 ohm 25 watt resistor in the AC line supplying the common leads of the silicon diodes. I left the old selenium stacks in place for appearance sake. 

Here is a photo of the underside of the chassis after the re-capping work was completed.  Upon initial start-up the 30 Kilovolt 2500 picofarad doorknob capacitor in the high voltage supply, shorted out.  I was able to obtain a new part on eBay.  After fabricating some custom mounting hardware to adapt the new doorknob capacitor to the high voltage cage, we were back up in running.

After the chassis was re-capped and operating on the test bench, the lack of ventilation in the HV cage caused the original horizontal output transformer to overheat and burn out.  I was lucky to have my good friend John Folsom “Mr. Early Color TV”, donate a new transformer for this set.  It was probably the only replacement transformer of this type in existence.  John Folsom is truly a very good friend and I am eternally indebted to John for his most gracious contribution to this restoration.  After installing the replacement transformer that I received from John, I cut a 3 inch hole in the side of the HV cage and installed a small electronic ventilation fan in the side panel.  The new transformer is now running very cool and no longer overheats.  It appears that RCA also decided that a design change was necessary to make the transformer run cooler.  You will notice that the black iron ferrite core of the replacement transformer (the transformer on the right in this photo) is larger than what was used in the original transformer (pictured on the left).  I suspect that a larger core was used in the newer design to help dissipate heat so the transformer would run cooler.

It is quite common for the deflection yoke covers in these early color sets to disintegrate and the deflection yoke cover in this set was no exception. These black plastic covers are made from an early form of plastic known as CAB (cellulose acetate butyrate).  Many early knobs on TV sets were also made of this plastic.  The problem is CAB degrades with time.  So once again it was necessary to create a replica part from scratch.  Fortunately this is fairly easy to do if you have the proper equipment.  For material I use .040” ( part number 269-9115)   and .080”(part number 269-9117 ) Evergreen brand, black styrene sheet plastic that I obtain from Walther’s Model train supply;   http://www.walthers.com 

I start with by cutting a square of .080” styrene sheet large enough to make a circular disc the size needed for the deflection yoke I am working with.  I drill a 3/8” hole in the center of the piece of styrene and mount the styrene onto a special fixture on my machine lathe.  Then, using the lathe, I cut the styrene into a precise circular disc, the exact diameter that I need.  I also cut a hole in the center of the disc in the same manor. 

Then I cut 2 strips of .040” thick styrene to make the edge of the cover.  The parts are glued together with a special cement designed for “fusing” styrene.  For an exact step by step tutorial on how I make replacement deflection yoke covers, see “Replica Yoke Covers” in the “My Methods” section of the menus in the left window.  

This is a photo of the deflection yoke with it’s newly replicated back cover installed.


Refinishing the cabinet was fairly straight forward.  I first used lacquer thinner to wipe down the entire cabinet.  This also acts to remove wax and silicone and to soften the old lacquer finish so that the new lacquer will adhere well.  Some areas needed a bit of touch up with stain.  So I blended 2 colors of water born stain together to get a good match.  I then proceeded to apply 7 coats of acrylic automotive lacquer.  Between each coat I waited 48 hours and then wet sanded the dry lacquer with 320 wet sand paper to achieve a nice flat surface.  When the final coat was dry, I wet sanded with 400 wet sand paper and then buffed with a power buffer and polishing compound to achieve a nice satin finish.

The cabinet stands on 4 tapered wooden spindle legs that have a solid brass ferrule at the tip of the leg.  The brass looked very bad so I removed the brass ferrules and polished them and coated them with 2 coats of acrylic lacquer.  I sanded the wooden spindle legs, then re-stained them and finished them with several coats of clear acrylic lacquer.  Then I re-attached the brass ferrules to the legs and installed the legs on the cabinet.  Here is a photo of the refinished cabinet.  Notice the brass ferrules on the legs.

There were some trim items that needed to be refinished also.  Around the safety glass, is a brass picture frame. They are made from solid brass. I buffed them with a large Scotch Bright wheel on a polishing arbor.  Then I use 0000 steel wool to buff the brass to a fine satin finish.  The brass surfaces were sealed with 2 coats of clear lacquer to prevent tarnishing.  For more details on how I refinish solid brass trim pieces, see “Brass Refinishing” in the  “My Methods” section of the menus in the left window. 

The “pencil box” control door below the screen was in very good condition but the brass chevron, RCA Victor emblem, on the control door, was also badly tarnished.  I removed the chevron and gave it the same treatment as the brass picture frame around the safety glass. And before re-attaching the chevron to the control door, I coated the control door with 2 coats of clear lacquer to create a “like new” finish.  When the lacquer was dry, I re-attached the RCA chevron.

The chassis needed to be cleaned so I spent some time polishing it with copper polish.  This set is supposed to have a black, ventilated, steel cover over the selenium power supply rectifiers, but it was missing on this set.  The cover is the same as the one used on the CT100 chassis.  Fortunately I had a CT100 chassis with the correct cover, and I used the CT100 cover as a model to duplicate an exact replica.  I ordered some perforated sheet steel from the McMaster Carr company, along with some sheet steel.  I also purchased a spot welder on eBay, to use in the fabrication process.  It took about 4 hours to cut, bend, drill and spot weld the sections together, but the finished cover is almost indistinguishable from the original.

In addition to the missing rectifier cage cover, the set was also missing the metal back.  The 21CT55 back is very similar to the back used on a CT100, except that it is about 4 inches taller.  So using a CT100 back as a model, I fabricated a new steel back for this set.  I started with a piece of sheet steel and cut a large rectangular hole to form sort of a picture frame.  Then I spot welded a piece of perforated steel to the picture frame.  I used the CT100 back as a pattern for drilling holes for the wood screws that fasten the back onto the cabinet.  I also made holes for the line cord and for some other controls.  I also took a piece of sheet steel and engraved it on our Hermes Vanguard engraving machine, labeling the names of the controls.

I didn’t have the plastic cupola for the bump out where the picture tube neck sticks out, so I needed to figure out something I could use.  I found just what I needed at the pet store. At the pet store they had a large assortment of stainless steel pet food bowls of various shapes and sizes.  I found one which was of the proper shape and size to make a replacement bump out for the picture tube neck.   Here are some photos of the new back, showing how it’s constructed.

About a year after I finished this restoration, Collin Wood, the person I purchased the set from, was able to locate the original back for this set, and it is now on the set.  I still have the replica back, which I fabricated, just in case another collector might someday need it for a 21CT55 that is missing it’s back.

The polyethylene CRT shroud needed a good cleaning and so did the purity magnet ring around the front of the CRT shroud.  At some point in the life of this set, somebody cut off 2 inches of the front lip of this polyethylene CRT shroud for some unknown reason.  The 2 inch piece was still sitting around the CRT bezel so I obtained a hot air plastic welder on eBay, and some polyethylene welding line and I was able to re-attach the 2” piece to the body of the CRT shroud.  Welding polyethylene is a process of using a stream of hot air to melt the polyethylene and also feeding polyethylene rod into the joint.  Proper control of the temperature of the air at the tip of the welder nozzle is critical.  I regulate the temperature of the welder with a variac and adjust the air flow of the compressed air through a pressure regulator.  The process of welding polyethylene is somewhat like soldering or brazing.  With the repair made to the polyethylene shroud, I was ready for final assembly.  Here is a photo of the cabinet with the picture tube installed with the shroud and associated components

I spent a good deal of time working on getting the convergence looking good.  FYI the convergence chassis is known as CTC-3. The main chassis on this set is known as CTC2B.  And that explains why the next RCA Color TV chassis in production is the CTC-4.  Here is a screen shot of a cross hatch pattern and a test card displaying excellent geometry.

Here are a couple shots of the rear, with chassis installed, and a shot with the back attached. And a front view of the final restored cabinet.

And these are scans of some actual advertising from RCA promoting their new 21 inch compatible color television set, the 21CT55.  These images are courtesy of Wayne Bretl.  Thanks Wayne!

I loaded my Wizard of Oz DVD into the DVD player and after some more adjusting, I was presented with a wonderful, display of brilliant color.  Here are some screen shots from Oz on the restored 21CT55, the world’s first production 21” color TV.  Pretty impressive for 1955 technology.