RCA Model CTC-11 Color Television (1962)

              

              

              

This RCA CTC-11 was my first color television restoration. Collectors call these early color TVs "roundies" because their picture tubes are round rather than rectangular.

I hadn't been looking for a roundie, but this deal was too good to pass up. The owner contacted me by email, offering to trade it for my little Scott 210-B mono amplifier.

I liked the Scott, but I had never used it much, and it had cost me only $7 in the first place. After restoring dozens of radios and several black and white TVs, a color TV would give me something new to learn.

Pickup

The TV was located about 100 miles away. Before completing the trade, the owner showed me that the TV worked, with a decent picture. He had owned the TV for a number of years but never really used it. A high school teacher had given him a new picture tube, so that vital part should be fine for a long time.

It took two men, the owner and his Dad, to load it into the back of my wife's SUV. The only way it would fit was lying on its face (with all knobs removed, of course), with about 1/4 inch of space between the TV cabinet and the SUV's ceiling. The cabinet back was missing, so great care was needed to avoid snapping off the neck of the picture tube.

When I got home after dark, nobody else was there to help me, but I was itching to get the TV out. The television was much too heavy for me to lift myself. The next photo shows how I extracted it. I propped an old door on the SUV's tailgate, covered it with cardboard and an old blanket, and very slowly slid it down the makeshift ramp. If somebody else had tried this, I would have called them nuts, but eventually the TV was standing upright in the garage.

The television was filthy, with a scarred cabinet top, but I had dealt with such things before. The question was whether the electronics were restorable.

First Look

The owner had played the TV with no fireworks, so I figured it was not too risky to turn it on. Here are screen shots of the unrestored set, using a rabbit ear antenna as well as a DVD source.

An experienced technician will instantly see various defects in the image, but the good news was that the TV was basically functional. The picture was bright and colors such as flesh tones were rendered pretty well.

  

Some of the defects, such as color purity, are simply a matter of adjustment after the electronics are restored.

With any luck, I should be able to restore it by replacing the power supply electrolytic capacitors, cleaning the controls, and then adjusting for best picture. The cabinet top will need to be stripped, but I can just touch up the rest.

Electronic Restoration

Here is my first look at the television's innards. The main chassis is mounted on its side. The convergence subchassis is mounted above the picture tube. A little subchassis (not visible here) projects through the front of the cabinet and holds controls for vertical, horizontal, contrast, and audio tone adjustments.

Version information appears on the chassis and cabinet.

  

The CTC-11 uses 25 tubes and one 6CW4 Nuvistor.

Tube Type Function
V1 6BZ6 1st Video IF Amplifier
V2 6GM6 2nd Video IF Amplifier
V3 6AW8A 3rd Video IF / Sync. Sep.
V4 6AW8A Video Amp. / Color Killer
V5 12BY7A Video Output
V6 6DT6A AGC Keying / Noise Inverter
V7 6EW6 Audio IF Amplifier
V8 6DT6A Audio Detector
V9 6AQ5A Audio Output
V10 6EM7 Vert. Mult. / Vert. Output
V11 6CG7 Horizontal AFC / Horiz. Osc.
V12 6DQ5 Horizontal Output
V13 6AU4GTA Damper
V14 3A3 High Voltage Rectifier
V15 1V2 Focus Rectifier
V16 6BK4 High Voltage Regulator
V17 6AU6 Chroma Bandpass Amplifier
V18 6EW6 Burst Amplifier
V19 6AL5 Chroma Sync. Phase Detector
V20 6GH8 Chroma Ref. Osc. & Control
V21 12AZ7 X Demodulator / Y Demod.
V22 6CG7 R-Y Amplifier / B-Y Amplifier
V23 6CG7 Horiz. Blank. Amp. / G-Y Amp.
V24 21FBP22 Picture Tube
V201 6CW4 RF Amplifier
V202 6EA8 Mixer / Oscillator

Nuvistors and New Vistas

The CTC-11's 6CW4 "nuvistor" is actually a tiny tube. Introduced by RCA in 1959, nuvistors were one of the last developments in tube technology; like the recently-developed transistor, it was smaller and more rugged than a conventional tube. In this photo, the arrow points to the nuvistor used in my CTC-11 tuner:

The nuvistor is much smaller than the nearby 6EA8 tube, which is the all-glass "miniature" type popularized after World War II.

RCA color TVs of the early 1960s sported a "New Vista" badge under their screens, with a COLOR sign that changed colors as you moved around the room. Here's a view of my badge:

The "New Vista" marketing term played on the word nuvistor and dramatized the new world of color television viewing. RCA used it extensively in its 1960s TV advertising. You can read much more about nuvistors in the article "Nuvistor Valves" by Stef Niewiadomski.

Cleaning Controls and Tube Pins

Here is the unrestored chassis removed from the cabinet. The 21-inch picture tube is very heavy and normally would not be removed for service.

  

Notice the four cylinders with flat tops. These contain electrolytic capacitors—a total of ten capacitors among the four cans. We'll return to these presently.

After doing some initial cleanup, I tested the tubes and cleaned their pins. Not surprisingly, since the TV worked, they all tested good. I also cleaned the controls (volume, etc.) by spritzing DeOxit cleaner into their cases and working the controls back and forth several times.

Below is a small sub-chassis that contains seven controls. Four of them protrude through the TV's front panel and have knobs: horizontal hold, vertical hold, contrast, and color tone. (The horizontal hold control is an adjustable coil that requires no cleaning.)

The other three potentiometers on the sub-chassis control killer threshold, vertical linearity, and height. They are accessible with a very thin screwdriver blade through the hollow shafts of the three pots listed earlier.

The CTC-11 contains more potentiometers—there are 26 in all—but the remaining ones are for adjustments such as convergence or high voltage level, which I don't want to touch at this stage.

I knew the tuner needed cleaning, as well. Tuning was pretty hit and miss during the initial tryout. Some channels needed jiggling to get a stable picture with correct colors.

The tuner comprises another sub-chassis, mounted on the main chassis with three screws. Removing the RF output cable (it has an RCA jack) lets you swivel the tuner around without unsoldering any of the other wires.

You remove two metal shields to expose the tuner innards. The big shield slides downward. You may have to help it get started by gently pushing with a screwdriver blade at the top. A smaller shield is mounted near the front with two twisted metal tabs at its top. Carefully bend the tabs straight so that they can move through their slots, allowing the shield to slide down and off.

With access to the phenolic wafers, I carefully sprayed a little DeOxit on each contact assembly and switched the tuning knob through all of the channels a number of times.

Capacitor Replacement

Although the original electrolytic capacitors were working—at least for the moment—I decided to replace them for safety and reliability. That's easier and cheaper than replacing an expensive part like a power transformer if one of them fails. Besides, healthy capacitors are vital for a healthy power supply.

Here are thirteen new electrolytics, ready for installation.

Sometimes you can replace multi-section electrolytics by disconnecting the originals and wiring new caps under the chassis. The area under these cans is cramped, however, so I "restuffed" two of the cans (holding a total of five capacitors), removing the old innards and putting fresh capacitors back in their place. I left the old cans intact on top of the chassis, to preserve its original appearance.

Here's a "wordless workshop" on how I restuffed one of them: C1, which contains a single electrolytic in its can. The replacement was a little too long, but I made it fit.

              

The small capacitors in this TV are ceramic or dipped Mylar types, which are usually reliable, so I left them alone unless I had a specific reason to replace one. My article on capacitor replacement has much more on the general topic.

Audio Troubles

With fresh electrolytics installed, I cautiously powered up the TV and was delighted to see a good picture. The only thing missing was the sound! All I could hear was a faint background hiss with the volume turned all the way up.

I first checked the obvious. Perhaps I had broken a speaker connection when taking the chassis in and out of the cabinet or (shudder!) miswired one of the electrolytics affecting the audio section.

No smoking guns appeared, so I began trying to diagnose the problem. The CTC-11 audio circuit is conventional and not very complicated, using three tubes. Here's the audio portion of the schematic and the audio board, top and bottom. From left to right in the top view are the sockets for the 6EW6, 6DT6A, and 6AQ5A tubes.

     

Using a basic repairman's test, I found that a live soldering iron touched to the wiper of the volume control made a buzz in the speaker. This proved that the output section (6AQ5A tube) was working and the speaker was connected.

I then tried injecting a modulated audio signal at pin 1 of the Audio IF tube (6EW6). No sound, indicating trouble somewhere between that tube and the output tube.

Quick voltage checks showed some anomalies. The 6AQ5A plate voltage was somewhat high, measuring 271 volts rather than 250 as specified in the schematic. The 6EW6 plate voltage was extremely high: 211 volts rather than 150.

The only practical way to test voltages with the chassis in the cabinet is with a tube adaptor like this one.

The adaptor extends the tube and provides a test point for each pin. I got a sack of these at a swap meet for a few bucks.

The wacky voltages on the 6EW6 did not bode well, and substituting an equivalent known-good tube made no improvement. Incidentally, although I found a good substitute for the 6EW6 in my stash of six-volt tubes, I later noticed that the TV itself has two tubes that you could swap for a quick test. The burst amplifier is a 6EW6 and the first video IF amplifier (6BZ6) is equivalent.

I pulled out the chassis and made a lot of resistance checks on the audio board, following the chart in the service manual.

This revealed some interesting things, including the fact that two resistors—apparently factory originals— had different values than what the schematic showed. I decided not to disturb them for the time being, although one was 270 ohms rather than 47 and the other was 33K ohms rather than 6.8K. Sometimes a manufacturer will make "rolling changes" in a design that aren't reflected in the documentation.

Fresh out of ideas, I called on the rec.antiques.radio+phono newsgroup for help. I got loads of helpful advice, including a tip that solved the problem.

Experienced TV techs remembered that CTCs had notorious problems with solder joints that connect the boards to chassis ground lugs. It was also noted that the high 6EW6 voltages were consistent with the tube's filaments not heating up, again suggesting a bad ground.

I hadn't noticed any ground problems with the ohmmeter and those connections all looked good to the naked eye. (And it was impossible to see whether the filaments glowed because the top half of this tube is silvered and opaque.)

Nevertheless, I acted on this advice, resoldering all of the ground joints and reflowing a couple of dodgy-looking places on the board. While I was at it, I cleaned and re-cleaned the socket for that tube, in case it was making a bad connection.

Voila! I reinstalled the chassis for what seemed like the hundredth time and was rewarded with excellent audio. Without help from the gurus in that newsgroup, I may never have stumbled on the right answer.

2010 Update. A couple of years after I published this article, the previous owner ran across it and sent me an email. He remembered that when the audio went out, he had gotten it back by wedging a matchbook cover under the base of the 6EW6 tube! That pressure apparently reestablished contact, either in the tube socket or with an intermittent ground.

My Kingdom For a Blue Lateral Magnet!

Flushed with success, I decided it was time to learn how to adjust the TV's purity and convergence, color-specific procedures I had never performed before. The service manual summarizes these tasks, but doesn't go into much detail. A qualified technician was supposed to understand them already. I had a little book, the RCA Color TV Service Handbook, which explained them somewhat better, but didn't have much detail on specific models.

I had trouble identifying certain adjusters from the blurry little photo in my photocopy of the schematic. Again, one of the experts solved the mystery. Two parts were absent! Can you identify what's missing from this picture?

The AWOL pieces are the purity rings and blue lateral magnet, normally mounted on the picture tube neck behind the convergence assembly seen in the photo. Although the TV picture was surprisingly normal, given their absence, you could never get it right without those parts. Fortunately, I found another collector with spares he was willing to donate.

New Parts to the Rescue!

Here are the new parts, blue lateral magnet on the left, purity rings on the right.

The next photo shows the parts installed on the picture tube neck. The purity rings are slid on immediately behind the convergence assembly (the gizmo with coils and wires, seen in a previous photo). Farthest back on the neck is the blue lateral magnet, which is held on with a spring.

Let's note three other things in the previous photo. First, the big ivory plastic doughnut is the TV's main yoke, which focuses the electron beams on the front of the picture tube. We'll be sliding that out and in during the purity adjustment.

Directly behind the yoke, the convergence assembly has three sets of coils, two of which are visible here. RCA used colored wire on the coils and connecting wires for identification. The assembly for the red electron gun has red wires, and so on.

Finally, note that each coil has a little plastic stick, held in a metal clip and protruding back at a slight angle. (The rectangular stick has a series of holes in it). These sticks hold magnets that can make fine changes in the position of each color's electron beam. I would become very familiar with these little sticks later on!

Before making color adjustments, you normally check and adjust all "black and white" settings, such as focus and vertical linearity. In trying to set vertical height and linearity, I discovered that the vertical centering control on the back of the chassis was defective. It had only one usable position: turning it at all collapsed the entire screen into a horizontal line.

I made a note to replace that control later, and adjusted the vertical as best I could.

What Are Purity and Convergence?

Purity and convergence are two concepts not used in the black and white TV world, which I was more familiar with at the time. Let's briefly define each one.

TV pictures, as you probably know, are made by lighting up tiny dots on the screen. On a black and white TV, each dot can be black, white, or any shade of gray. On a color TV, each dot can be one of three colors—red, green, and blue— or any combination of the three. A black and white picture tube lights up dots with a single electron gun, while a color picture tube uses three guns, one for each color.

Purity is the ability of the TV to display a given color evenly across the entire screen, without any blotches or variations. On a set with bad purity, the screen will have blobby areas where colors are inaccurate, even if the picture is otherwise sharp and clear.

This pre-restoration photo shows an obvious purity defect. The flesh tones in the man's face look fairly natural, but notice how they become too blue in the lower right of the screen.

Convergence is the TV's ability to line up the electron beams from all three guns so that they fall precisely on every dot on the screen. On a set with bad convergence, images may be outlined or ghosted with wrong colors.

To adjust convergence, you need a TV pattern generator. Here is mine, a simple model.

To check convergence, I set the generator to display a crosshatch pattern with a single dot in the center. This photo shows poor convergence. I have deliberately misadjusted the magnets to show the effect clearly.

Look at the three colored dots in the center and the mismatched color lines throughout the screen. In a properly-converged TV, the three colored dots will align to make a single white dot. The horizontal and vertical lines will likewise be white.

Note how the horizontal mismatch becomes worse as you move out from the center, and how the mismatch is different on left and right sides of the screen. Every part of the image must be adjusted separately to get correct convergence.

Purity Adjustment, Take One

Adjusting purity is simple in concept. You turn off the blue and green electron guns, leaving only the red one active. Then you adjust the yoke and purity rings until you have an even red color filling the entire screen.

A terse description of the process will start with something like "kill blue and green guns," to which I initially responded, "Say, what?"

I found a better description in the service manual, which tells you to connect those guns to chassis ground through 100K resistors, using test points shown in a diagram. That's what is happening here.

I set the pattern generator to display a uniform blank screen. When all three color guns are turned on, the screen is gray. When blue and green are turned off, the screen is red.

When setting the purity, I had skipped the initial step in which you loosen the yoke, slide it back, then slide it forward until you see an even, deep red color on the entire screen. The purity rings may be adjusted as needed at both stages to reduce impurities.

Here's what I saw with the blue and green guns turned off and the yoke left in its original position. A big red ball. (Ignore the moire effect in the photo, which is an artifact of my camera.)

I tried manipulating the purity rings, more to learn about them than anything else, but didn't notice any great changes when viewing the big red ball. The ring can be adjusted in two ways: by rotating the entire assembly around the picture tube neck, and by spreading the "ears" of the magnetic collars closer or farther from each other.

The red color looked pretty even to me, so I decided to call the purity good and move on to adjusting convergence.

Convergence Adjustment, Take One

As mentioned before, the three sticks on the convergence assembly each hold a magnet. Sliding a stick in or out moves its magnet closer to, or farther from, the corresponding electron gun. For red and green, this moves the corresponding color dot on a diagonal. For blue, it moves the dot up or down.

The sticks primarily affect the central screen area. For the edges, you need to adjust another set of controls on a separate PC board. Moving the sticks on the convergence assembly is called static convergence. Adjusting the other controls is dynamic convergence, and we'll get to that later.

The next photo shows the crosshatch pattern after my first attempt at adjusting convergence.

This is fairly decent convergence. The center dot is white, as are the lines throughout most of the screen. Only the edges are off somewhat.

How does this affect an actual TV picture? Below is an off-air photo that I took at this stage, using a rabbit ear antenna and digital converter.

This picture is definitely better than the pre-restoration photo that showed a man with a blue neck. Slight imperfections remain, of course. James Spader's skin looks a tad purplish, but I hadn't bothered to tweak the Tint control before taking this picture. The vertical height and linearity are still a bit off, but I hadn't messed with them since finding the bad vertical centering control.

I was pretty content with my first foray into color adjustments. The picture had improved, and—most important of all—I hadn't made things worse!

Purity Adjustment, Take Two

Since I hadn't done the first purity adjustment by the book, I decided to start over. I wanted to learn these procedures well enough to do them confidently in future projects.

I began by sliding the blue lateral magnet and convergence assembly way back on the CRT neck, then loosening the clamp on the yoke and sliding it back as well. I also turned off the green and blue guns (see above).

The instructions now tell you to start sliding the yoke forward until you see a red ball in the middle, using the purity rings to make the ball as round and deep red as you can. Here's what I saw.

It surprised me a bit that the entire lit portion of the screen was offset on the CRT face. However, I was able to use the purity rings to get a nice round red shape in the center, rather than a misshapen blob stretching out in one direction or another.

As I slowly pushed the yoke forward, the image expanded and also re-centered until red filled the screen.

Looking closely, I thought I could see a very slight crescent of magenta discoloration in the extreme upper right, and an odd, faint wrinkle in the left margin. Other than that, the screen looked great.

Convergence Adjustment, Take Two

Before setting purity, the manual had told me to set the controls on the dynamic convergence board to the middles of their ranges, which I did. Here's the infamous board with a diagram identifying its controls.

  

We'll return to this beast later, but notice that it has twelve controls: nine potentiometers and three coils. Near the upper right is a component that puzzled me at first. It's the gray item with a brown cylindrical core and four gray stacked plates, much like a little selenium rectifier.

I learned that this is indeed a rectifier, with three diodes in one package. The topmost plate was very loose—not a good sign. We'll return to that guy, too.

Back to convergence. The instructions say to begin by adjusting the three sticks with magnets until the three central color dots become a single white dot. This was impossible, no matter how I slid the magnets in and out. Here's the best that I could do at this stage.

Look at how the blue lines droop in the middle. Awful. Red and green wouldn't converge to pure white, even in the very center. This was worse than the "bad convergence" photo I had taken before changing anything at all!

I decided to cheat and try adjusting controls on the dynamic convergence board. This improved things somewhat, but the convergence was still very poor.

I noted two things while adjusting controls. One of the pots was almost impossible to turn. Worse, if I pushed a fingertip on the loose plate of the little selenium rectifier, the blue lines jiggled all over the screen. Time to power down and replace some parts. At the very least, I needed to replace the vertical centering pot and that rectifier. It might be worth checking all of the pots on that board, too.

Vertical Centering Potentiometer

Before replacing the vertical centering potentiometer, I took it apart and attempted a cleaning.

After cleaning and reassembly, the pot showed the same symptoms. Meanwhile, a newsgroup member offered to mail me a replacement for free, so I said, why not?

The replacement looked good on the outside, but completely failed to register on my ohmmeter when tested. Here's why.

The innards were burned and melted—not salvageable. I went online and ordered a new part. With the fresh pot in place, I was able to center the screen and get acceptable vertical linearity.

Convergence Board Repairs

With improved linearity, I ran through convergence again and realized just how dodgy some of the potentiometers were. One was almost completely stuck, and two others were very stiff. This prevented me from obtaining good horizontal convergence of red and green vertical lines near the screen edges.

New replacement potentiometers are not available nowadays, so once again I put out a call to the faithful, and a fellow TV nut found something in a parts stash that would fit.

Meanwhile, I replaced the board's selenium rectifier with three fast-response diodes. Again, here is the old rectifier still on the board.

When I unsoldered the legs of the rectifier, the whole thing just fell into pieces! The following photos show the new diodes next to the old parts, and the new parts installed on the board.

  

With new diodes in place, what could be more fun than to re-converge the television?

Adjusting High Voltage

But first, I reread the manual's setup instructions and noted the section about adjusting high voltage output. I had avoided this earlier because the high voltage adjuster is under the chassis and I had no extension cables to power up the TV outside its cabinet.

Another collector pointed out that, with care, I could set the chassis sideways behind the cabinet and power up with the existing cables. Slapping a hand to my forehead, I found an old ice chest the right size, and did just that.

Testing high voltage involves disconnecting the HV lead from the picture tube and connecting it to your HV probe, which in turn is grounded to the chassis. For this I used my trusty Sencore probe, seen on the bottom of this photo.

If you haven't messed with high voltage before, I advise caution. The black and white TVs that I had previously worked on could generate a few thousand volts, but a color television runs much higher—in this case, over twenty thousand volts.

After insulating and taping the connections from the picture tube cable to my probe, I measured exactly 20 KV, which is high enough to run the set, but the schematic specified 21.8, so I adjusted it to that.

Convergence, Take Three

Actually, I had played with convergence more than three times by now, but let's call this number three. I did the full-dress procedure, starting with the twiddle sticks on the convergence assembly and very carefully following the instructions.

One thing I had earlier skipped was the instruction to redo the static convergence as needed during dynamic convergence. I didn't skip it this time, and eventually the three little colored dots in the center formed a pure white dot—something I hadn't seen since I originally disturbed things.

Now the crosshatch pattern produced nice white lines on about 80% of the screen. Red and green vertical lines near the edges still wouldn't converge, however.

I took a couple of screen shots using a rabbit ear antenna and digital converter, with a modern solid-state TV on top of the RCA for comparison. Let's look.

  

The colors on the CTC-11 look pretty true, including flesh tones, which are hard to render.

The first photo shows some red/green misconvergence. Note the color fringing on the upper right edge of the woman's hair and the more obvious red/green defects in her costume at the bottom.

The world of the M.A.S.H. guys is drabber, so an average viewer wouldn't see much to complain about, except slight fringing in the "ion" logo at lower right.

Convergence, Take Four

Meanwhile, I had gotten a couple of new potentiometers in the mail. Here's a view of these cheap little critters.

I replaced the worst potentiometer on the board, but still gained no improvement after yet another full adjustment. Notice how red and green lines are bowed out at the top and bottom of the screen.

All of the capacitors on the convergence board were original, and although "orange drop" (dipped mylar) caps tend to be reliable, these were over forty years old. I replaced those caps and, while I was at it, the four 100-ohm resistors as well.

The new pot is the white one at the upper left in this view. The new caps are mostly little yellow guys. Three of the capacitors had oddball values, such as .082 mfd, which I produced by piggybacking a pair of caps in parallel.

Referring again to the diagram, the pot that I replaced is the Vertical R-G Difference Amp. The two pots that should solve my red/green convergence problem are in the middle row: the Vertical R-G Master Amp and the Vertical R-G Master Tilt.

Rats. After installing 13 new components on the board, the problem persisted.

Would the Real Convergence Board Please Stand Up?

While working on the board, I had noticed a couple of components not shown on the schematic. At far upper left in the previous photo, you can see the top of a cylindrical metal can rectifier, next to a 270-ohm resistor. A friend in a TV forum told me that these were used in models CTC-15 and higher, and are not present in the CTC-11.

In short, my convergence board and assembly belong to a different, later model. This does not sound good.

The two additional components lead to one of the board's R-G controls, so it's not inconceivable that they might affect R-G convergence. Comparing the CTC-11 and CTC-15 schematics, it appeared that these were the only differences, apart from a different value in one of the pots. Crossing my fingers, I temporarily disconnected the CTC-15-specific components and installed a jumper.

Foiled again! Still no improvement.

Repairing a Broken Wire

When I mentioned the mismatched board and assembly in another forum, one of the members half-jokingly suggested reversing connections to the Red and Green coils on the assembly, to see what happened.

I wasn't desperate enough to start rewiring coils, but I did stick my head into the cabinet to see how tricky that might be. (Answer: pretty tricky.)

Looking closely at the Green coil, I spied something new. A wire had broken off its terminal. Since the wire end was hanging very close to the terminal, this wasn't obvious to the casual eye.

After I repaired that wire (it's the white-green lead), it was not hard to get improved convergence.

        

Yes, convergence really does work better when all the wires between the board and the coils are connected!

Declaring Victory

Television oldtimers have told me that convergence in these sets always involved compromise. The controls are interactive, so a tiny change for the better in one area may nudge things slightly off in another. At some point you need to quit monkeying around and pick the picture you like best, understanding that it'll never be perfect.

I did four more go-rounds at convergence and finally declared victory. Now this a TV that I can enjoy watching. The first of these images is a still photo. The second is a link to a brief video clip. (Please excuse the tinny audio; the microphone in my digital camera is the size of a pinhead.)

  

Cosmetic Restoration

As found, this television had an incorrect channel selector knob. It also was missing the fine tuning knob. I got replacements from a fellow collector. The tuning knob looks close, but I'm not sure it's an exact match for this cabinet. The fine tuning knob isn't quite correct, either; it's a hair too thick for the opening, and tends to bind. I have the right number of small knobs, but two of them are too dark for the cabinet, more black than medium brown. Drop me a line if you happen to have any of these items in your junkbox.

The cabinet needed more than light touchups. The finish was badly faded from exposure to sunlight. The original color is a medium dark brown, but the side panels have faded to a sickly greenish yellow in some areas. The top also had deep gouges from dragging heavy equipment across it.

     

I avoid sanding when possible, but the gouges left no choice. Here is the top after I sanded it and wetted it with mineral spirits to get an idea what the grain would look like.

I used a rubber sanding block to make sure the old finish was removed evenly, starting with 220 grade and going to 320 and 400 grade paper. This cabinet should be attractive when I'm done.

The rest of the cabinet required no sanding, but the discolored finish needed stripping. There also was a dent in the metal speaker grille, so I decided to remove everything from the cabinet, rather than try to work around the CRT, control panel and speaker grille

Removing Bezel and Control Panel

The first step is to remove the picture tube. Be careful—it's heavy! This is best done with a helper.

I left the convergence board, yoke, blue lateral magnet, and purity rings attached to the picture tube. Removing these would force me to readjust the purity and convergence from scratch after reinstallation. This way, perhaps I can get by with a minor tweak to the convergence. The convergence board must be unscrewed from the cabinet, of course. I temporarily taped it to the convergence yoke and CRT neck.

Moving a big picture tube involves a risk of implosion. I wore safety goggles, gloves, a thick jacket, and a scarf around my neck. Catching a shard of flying glass in your eye or jugular vein can really spoil your day!

The CRT is held in place by four metal straps fastened with sheet metal screws. Loosen the bottom ones first. Be ready to catch the tube after loosening the second screw on top. Grasp the freed-up tube by the bell, avoiding stress on the fragile neck. Laying a towel or piece of cardboard inside the cabinet, will give the tube something to slide on as you carefully bring it out.

The control panel is removed by loosening eight sheet metal fasteners on the inside. The fasteners will slip off after turning them partway; you don't need to completely unscrew them. Be careful not to break the panel's plastic mounting posts. You also need to remove a horizontal strip of wood from the upper inside of the cabinet.

The bezel around the picture tube comes off after you remove several screws from the inside. The speaker board detaches complete with speakers and grille cloth. After removing the bezel and panel, I put the mounting screws back in their original holes so they wouldn't get lost or mixed up.

I stashed the CTC-11 parts in a spare room while waiting for the cabinet to be finished. Looks like a pile of junk, but I really will make it back into a television some day, I promise!

Stripping the Cabinet

I stripped the cabinet one side at a time, using a gel-type stripper.

After the stripper did its work, I removed it by scraping with an old putty knife and mopping with wet paper towels. When the cabinet was dry, I went back over that side with paper towels and lacquer thinner. Finally, I gave it a very light sanding to match its color and smoothness to the top.

Rinse, repeat. You get the idea. Here is the cabinet after a sanding session, trundled inside to escape a sudden rain. Earlier in this project, I had built a sturdy rubber-wheeled dolly specifically to fit this set. It has been a lifesaver.

That's as far as I had gotten by late October, 2009. The cabinet was stripped and ready for new finish, but the weather turned cold and rainy, not conducive to spraying lacquer outdoors. As winter set in, I pondered what to do.

Two Slight Detours

While this project was underway, I stumbled across a second CTC-11, priced at $1 in a local ad. Eager to learn more about color sets, I picked it up and plunged into its restoration. Soon after that, I ran across another bargain, a DuMont RA-103, and finished that restoration, too. Read about those projects by clicking on the images below.

  

Time for a New Cabinet!

In February, 2010, I gave up on finishing the cabinet myself and brought it to Michael Mueller, a Seattle furniture maker and refinisher. We agreed on a price and a couple of weeks later, I had the cabinet back, looking sassy. What a contrast to the battle-scarred hulk I had brought home months earlier.

  

Will I remember how to put all of these things together?

The speaker board, bezel, and control panel are back in place. Before reinstalling them, I cleaned and polished all of the plastic and painted surfaces with Novus Plastic Polish #2. Don't get too aggressive with the paint on the control panel. It's rather delicate stuff.

Installing the Picture Tube and Chassis

Now to replace the picture tube. The yoke assemblies and convergence board are still taped around the neck.

Before putting the tube back in, I donned a jacket and safety goggles. I also put an old towel in the bottom of the chassis compartment.

Installing a heavy picture tube by yourself is not fun. I finally got the job done, but it would have been easier with a helper. The CRT mount on this TV is just plain cheesy. After you maneuver the tube into its supporting front brackets, you secure it by screwing four bent pieces of sheet metal to braces. In hindsight, I should have fashioned some kind of temporary support to hold the tube in place while I fussed with these sharp metal strips and screws.

Oops. While rassling the CRT into position, I managed to snap a lead to the green convergence coil. Notice the loose green wire.

Slipping off the convergence yoke and resoldering the lead took only a few minutes, but this escapade defeated the purpose of leaving that gear on the CRT neck in the first place. Now I'll need to do a full-dress reconvergence. Oh, well—it might have been unavoidable, anyway.

A couple of tasks remain before I can reinstall the chassis. When I restored this set, I cleaned the tuner as I had done many radio bandswitches, by spraying DeOxit on the contacts and working the tuner through all of the channels several times. When restoring my second CTC-11, I found that the quick spray-on method didn't quite cut it. I got better results by dipping Q-tips in DeOxit and rubbing them on every contact surface, following up the cleaner with an electronic lubricant.

These wafer-type tuners are known to be troublesome, so I cracked this one open and took the time to clean it properly.

While I had the chassis on the bench, I also re-cleaned two controls that had acted a little scratchy after their first cleaning: the volume control and vertical hold.

Is It Really a TV?

Enough fussing, already—let's fire this thing up!

Hmm, less than perfect. The first photo shows wild misconvergence, a split screen, and a slight horizontal tilt. This is a monochrome scene from the beginning of the Wizard of Oz, so the general absence of color isn't a problem. As you can see from the image artifacts, the colors are all present, just not in the right places!

I found the way back to Kansas before long. Initial corrections took only a few minutes with the yoke, vertical controls, and convergence magnets. Since everything had been pulled off the CRT neck, I spent about an hour redoing the purity, grayscale, and convergence. (The "blue" crosshatch pattern is actually white; my camera makes most black and white TV images too blue.)

     

Here's the TV in my workspace after tweaking. Not bad.

Kindly Degauss After Moving!

Now, to take an "after" photo, showing the finished restoration in a less cluttered background. I moved the TV across the room and turned it around for better lighting.

Arrgghhh! What happened here? The Scarecrow's cornfield is on fire, Dorothy looks like she ate a green popsicle, and the Yellow Brick Road is yellow, orange, and purple!

     

I had read that moving an early color TV can disturb the colors, but I wondered whether the effect could be this drastic. A query to the Videokarma.org color TV forum quickly gave me the answer (Yes) and the advice to try degaussing.

Degaussing coil to the rescue! I got this one from a retired oldtimer.

Degaussing fixed the problem in about one minute. The procedure is simple. You stand about ten feet back from the TV, then switch on the coil and advance, holding it in front of you. When you reach the face of the picture tube, you slowly move the coil around in circles for about 30 seconds. Then you slowly back away at least six feet, place the coil flat on the floor, and switch it off.

Degaussing is necessary because the Earth has a magnetic field. The electron beams in the picture tube are directed by magnetism in the yoke, convergence magnets, purity rings, and convergence coils. In this case, merely shifting the TV's orientation in Earth's magnetic field undid some of my careful adjustments and sent the electrons astray.

Not long after this TV was built, manufacturers eliminated this problem by including a built-in degaussing coil that energizes briefly each time you switch on the set.

Degaussing can't hurt the picture tube. It's worth doing before any setup procedure such as adjusting purity, as well as after moving the TV. (Don't put an energized degaussing coil behind a TV like this, which may demagnetize the convergence magnets and purity rings.)

2011 Update

After using the TV occasionally for a couple of years, I noticed that the vertical linearity had gone off, and I couldn't correct it with the usual adjustments. The horizontal sync was also getting a bit twitchy.

When I first restored this TV, I had replaced some small capacitors on the audio board but I left all of the non-polarized originals on the sweep boards. In the meantime, my restoration of a 1958 CTC-7 had shown me how much the old "maroon drops" can degrade with age. They may not have failed completely, but they had grown leaky enough to create real problems.

Recapping the vertical and horizontal boards didn't take long, thanks to my recent practice on the CTC-7 and a Philco Miss America set.

        

Now, I could easily obtain correctly linearity and the horizontal was more stable, too. After returning the set to my office, I degaussed the picture tube and re-did the convergence for good measure. Recapping those boards was so easy that I'm tempted to give my CTC-11H the same treatment as a preventive.

Final Thoughts

Here's a final photo showing my CTC-11 at its best. The initial restoration took more than a year, with many time-outs and diversions, but I'm pleased with the result. This CTC-11 is a keeper!

Although setup procedures can be tedious, they're essential in every color TV project. Merely replacing capacitors may give you a color picture, but not one that's accurate and rich. I recommend the RCA Color TV Pict-O-Guide, readily available in used markets. It explains the theory behind purity, convergence, and so on, and describes every procedure with plenty of color illustrations. The 1964 edition of this book is just right for this model. The Sams service literature also describes the procedures, but in more summary fashion.

I wouldn't recommend an early color TV as a beginner's project, but it can be rewarding if you have some experience and a lot of patience. Again, I'd like to thank all of the folks in TV forums who offered generous advice. You know who you are!

Phil

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