Spent some time this evening on alignment of the color demodulator. Followed the RCA manual for the Chroma AFC, Chroma bandpass, and Color Matrix adjustments. Fortunately I've got an old Sencore color bar generator that generates the I and Q type pattern the RCA manual instructions are based on. Had to spend some time with the Sencore and a modern color set first to get the color bar generator working well enough. After alignment, it looks like this CT-100 can produce some decent looking color.

Purity is not good (see first pic), regardless of adjustment of the cross purity adjustment and field cancellation. Best is with no current in the purity coil (unplugged, or adjustment fully counterclockwise). Would you guys say this needs degaussing, or something else?

If it needs degaussing, can the field cancellation coil be drafted into service as a degausser with a variac, or is that coil capable of too little current and field to do the job? (I also don't want to burn it out, of course.)

The remaining pics are simply showing that we now have reasonable color.

Convergence still has big problems, so that will be a project for another day.

Overall, we're getting closer... :)

Great work Tom :thmbsp:

looking good. Not a expert on the CT-100 but I always start with a good degaussing. On sets that have them I start by fully retracting any perm magnets that may be used for edge purity (my CTC-5 had those). then use on of the large old school degaussing rings.

Thanks to a tip in a PM from one of our friendly VK members, I was able to get the purity much better (see first picture). What I had not yet tried was changing the position of the yoke along the neck of the CRT, and that helped a lot in terms of cleaning up the top edges of the raster for red purity. Now the color rendition is acceptable over the entire screen. The small amount of pink in the upper right corner is not easily noticeable in a normal picture.

I tried using the field cancellation coil as a degausser to see if any further improvement could be made. After all, the cancellation coil does bear some resemblance to the automatic degaussing coils built into newer sets. The wire size looked like it could handle an amp with no problem, so I applied AC current up to 1 amp (about 40 volts AC) and then backed off slowly. This had no effect on purity afterwards. It probably takes a lot more current than what I applied (automatic convergence coils give a nice buzz for the moment they work, and this coil never got into that regime). In any case, I'm not interested in testing the limits of the cancellation coil, since I might damage it, and the purity is actually pretty decent now anyway.

Worked on the convergence a bit. Horizontal convergence is working properly, and I was able to get good convergence across the horizontal axis (see second pic). The vertical convergence is not working properly -- adjusting both the vertical convergence amplitude and the vertical convergence shape controls has very little effect on the screen. Also the "smile" when probing at the plate of the convergence amplifier looks possibly inverted. I wonder if I have the phase of the new convergence transformer reversed? There may be some other problem in the vertical convergence circuitry, so I'll look into that further next time I get a chance to work on the set.

I also mounted the new convergence transformer inside the housing in which the old transformer was potted, and have positioned the solid state voltage tripler module inside the HV cage (not permanently mounted yet, but it soon will be). Also adjusted the range of the DC convergence control by adding 5 megohms on the top side (for some reason my control is only 10 megohms as opposed to the 15 megohms on the schematic; adding this resistor get the sweet spot properly within the range of the control).

I also made a slight modification to the focus control circuit. I'm still having loss of focus on very light or white screens. There isn't any evidence that this is caused by loss of regulation of the HV, so I think it is the focus voltage that is sagging or otherwise changing in high brightness scenes. I adjusted the range of the control (it is only 1 megohm as opposed to the 5 megohms on the schematic, so its range is really limited) and also increased the resistive load on the focus rectifier to both improve regulation and pull the voltage down into a range where good focus in properly centered in the range of the control. This may have improved focus stability, but I am not sure yet. It still won't stay in focus on the very brightest scenes. Nonetheless, it is watchable at this point.

"Oh the tenacity!" Seriously, I am envious (not jealous) and very happy to be able to follow this thread. So very few of these sets out there. My only "roundie" is a CTC-9 that is in the queue. I only hope that I can be as persistent and have good results.

Thanks for taking the time to do the work and share it with us.

Here is a tip on how to obtain a cheap degaussing coil if you ever feel the need to have one. Step one: Find a 'modern' CRT set on the curb or grab a 1$ thrift store special. Step two: Remove the internal degauss coil from it (sets with screens over 20' tend to have good degauss coils that can handle line voltage for a few minutes). Step three loop the coil into a ~16" ring, wrap that ring with electrical tape, and connect a line cord to the leads of the coil (make sure the cord is over 7' long if you do not want to use extension cords). Step four: test it out. If it does not get too hot to hold in ~4-9 minutes it should be good enough to get the job done.

Great idea, Tom. I would suggest adding a series on/off thumb operated switch in series with the AC line, as it is useful to be able to turn the coil on and off with the flick of a finger.

Or, there are several coils available on the bay: http://www.ebay.com/sch/i.html?_trks...at=0&_from=R40. Prices vary. The larger coils work best.

-Steve D.

Thanks for the tips on the degaussing coil. I checked eBay a few days ago, and only saw one for $39, which I thought was perhaps a little steep. Buyers for degaussing coils these days are probably few and far between! Anyway, there is certainly a nice selection of degaussing coils today, so I decided to order one.

I've parted out a few color sets over the years, and have always pulled the degaussing coils as a very useful source for a lot of nice magnet and coil wire in a very accessible form. I may have one of those fully intact somewhere, but I guess it will be nice to get one of the commercial degaussing coils instead of trying to make use of an old coil from a junked color set. Certainly sounds workable enough, though.

I've been making some measurements of what's happening when the focus goes out on bright scenes. I'm becoming convinced that the problem is focus voltage instability, not a HV regulation problem. The HV hardly budges, while the focus voltage changes by several hundred volts out of about 2.5 kV. Does anyone know of a solid state replacement for the 1X2B? I may also try a string of a bunch of 1N4007s just to see if a lower impedance rectifier would make much difference. I suppose I should check whether the voltage at the output of the 1X2B (as opposed to at the focus output to the CRT) is stable before worrying about the rectifier itself. It's possible that the voltage dropping potentiometer and resistors are the problem, driven by a change in current on the focus grid. The circuit looks like it was designed with the assumption that the focus grid would have little or no current flow, but I certainly seem to have enough to cause a problem.

I've been hearing from some of you that defocusing on bright scenes is par for the course on these sets, so this experimentation with focus stability is perhaps really more about understanding the design limitations of the set, and not true restoration, I suppose.

I'm also wondering if there is just a touch of gas in my CRT, which may be having some subtle effects.

Still working on the vertical dynamic convergence -- that remains one trouble spot with the set. It's watchable, but would be nicer at the bottom of the screen with better dynamic convergence.

Well, we've gotten far enough along on this that it looks like electrical restoration will be a success, so I guess it's a keeper. :)

Next I'll work on the cabinet. I won't post a blow-by-blow on the cabinet work, but I thought it would be nice to document the original as-acquired cabinet condition. Pictures attached. Will post some more when the cabinet is done.

A few more pics of original condition. Note some damage to the feet on the right side.

Last few pics of original condition.

Does anyone know if a decal set is available for this set? Would be nice to restore the front panel control decals.

I also don't have the original main knobs for the front. I imagine those will be hard to find. Any tips on a possible source would be greatly appreciated. I believe I saw an NOS tuning knob on eBay a couple of years ago. Didn't know I would ever need one then...

I've had the same question/supposition and have observed that the blooming/focus problem occurs on modern video, whether cable or DVD, especially commercials and DVD menus. There is no CT-100 focus anomaly ever with vintage video DVDs that were originally generated with the TK-41 (early Laugh In, for example) or restored 3-strip Technicolor movies. It is my contention that the TK-40/41 and the CT-100 were designed in concert, one with, and for, the other. And that well may be why they can't handle today's dynamics.

If that's correct, it's similar to the copy protection blocks that appear on the CT-100 screen but not modern TVs. Designers blanked out retrace lines on the CT-100; how could they have imagined a need to blank brute copy-protection!

Pete

I had CT-100 decals made by Scott Wright at Solidesign:

http://www.solidesign.bizland.com/decals.html

I looked through my box of CT-100 stuff and I guess I donated my last spare set. If you contact Scott, he can print you a new sheet from the old art file. He prints as many sets as will fit on one sheet, so then you will have some spares to share with future CT-100 owners.

Phil Nelson
Phil's Old Radios
http://antiqueradio.org/index.html

I believe it's less this above, and more the fact that anything taken off the camera and then sent through any kind of image processing, digital, or analog, can take the image and expand it's dynamics to the limits of the image window for transmission..... For example, while the camera may have photographed a dark scene, meant to be black, it may not show up as black unless it's tweeked a little by a video processor.... Photoshop also allows this for stills, it's called adjusting Levels.... Almost like adjusting the contrast so some of the grays are lost....

In a video, if the blacks are extended below black, they can effect sync, if white is extended beyond white, you get some noise in the sound...

Most likely anything sent over a live camera feed keeps everything out of the too black, or too white areas, Most likely the norm back in the day.... Today the black, and especially white in DVD menus are not photographed, but generated, and un naturally sent whiter than white, causing noise, blooming in that older set...

I still have them right here next to me, I don't think I'm going to use them after I saw what Bob's Halicrafter's resto looked like. You could really see the outline of the decal against the wood, it just looked out of place to me. I guess I can send them along to Tom, same price I got them for. :thmbsp:

Hi miniman82,

I was just about to send off an email to Solidesign, but if you're willing to send me a set, I'll do my best to put them to good use. Great to see how folks here share resources and tips.

Quick question here for anyone who has worked on these or faced a similar situation on a different set -- Is there a preferred way to get the safety glass off the plastic CRT mask? Looks like the original rubber or expanded foam seal liquefied at some point and ran downward a little, and then very helpfully turned to stone with quite good adhesive properties (see picture). I'm hoping not to damage the paint on the front of the mask, which might happen if I simply try to pry it apart. Maybe a little (but not too much) heat?

Tom

I have had to remove several safety glass plates from RCA plastic crt frames which were stuck together from the foam rubber gasget that was used. I found that if you saturate the rubber with WD40 or mineral spirits the rubber will start to get gooey and then it will be much easier to seperate the glass from the crt frame. AFter seperating the 2 pieces, I use mineral spirits and fine steel wool to clean the rubber off the inside face of the glass. The plastic frame is a bit more difficult to clean. I use a plastic "Bondo" spatula as a scraper to remove the bulk of the gooey rubber that was softenend by the mineral spirits. Any type of soft plastic will probably work so as not to damage the crt frame. Then when you have the bulk of the rubber removed from the crt frame, use a rag saturated with mineral spirits and rub the remaining rubber residue from the crt frame. I even had good results doing this on a CT100 crt frame and did not do any damage to the painted areas.

I did use the heat method on a CTC4 safety glass once, but the solvent method above works well if you are patient and there is less risk of breaking the glass.

RE: the decals issue. It is my understanding that if you are doing a complete refinish and you place the decals on wet varnish, and then apply several more coats to the cabinet, that the decals will be less visable. I have yet to try this method so I cant vouch for it. But Nick is correct, if you apply the decals on the surface, the carrier of the decal will be VERY visable.

There are various setting solutions that model builders use to brush over the decal after it's been first set. The solution softens the film, allowing the decal film to pull down tight against any surface irregularities when it dries, which eliminates voids under the film that show up as white spots when the film dries. Hiding the film edges becomes a process of applying many coats of clear finish over the area - enough so that the edges can be feather sanded in. There are various
thicknesses of decal films available too. However the thinner ones will be much more fragile to apply. I use to use this stuff back when I was into model railroading when I was younger. It was really amazing how many irregularities you cold conform a decal over.

I think during manufacturing that they used the silk screening process. There's no way they could have taken the time to apply individual decals, unless it was for a prototype.

On both my CTC-4 and CT-100, I heated the frame/glass with a pair of hair dryers. Slowly apply pressure to pry them away from each other, they should come apart with little effort. Bob's right, it's a PITA to get the crap off the frame. I used a razor on the glass and some goo gone, that worked fine. But I ended up damaging a little of the paint on the mask scraping it off; I guess I always meant to repaint the damaged areas, but apparently it hasn't bothered me enough to take the thing back apart to fix it. Most of it is out of sight anyway, but some of them do drip down a ways and are more bothersome.

Thanks for all the advice on getting the black crud off. I looked over all of the above, and ended up using the following procedure which worked well:

1. Heat the edge of the glass with a heat gun, gently prying the glass up with a screwdriver and inserting little spacers as I proceeded along. It didn't take much heat -- perhaps about 100-120 degrees F was enough to get things apart. Whole operation took less than 5 minutes to get the glass off.

2. Used a razor blade to get most of the crud off the glass. No problem. A little residue left behind was easily removed with paint thinner and a rag.

3. I didn't have any mineral spirits on hand, but tried paint thinner on the crud on the mask side. I found it is a very marginal solvent for the crud, and using paint thinner alone would have taken a very long time and a lot of rubbing (mineral spirits might have done better). What worked very well was to wet the surface with paint thinner, and then use a razor blade to carefully scrape the crud off, rewetting things as material was removed. This is probably much safer than trying it dry. The paint thinner softens the crud slightly, and more importantly, lubricates the surfaces and the razor blade, so you have a nicely lubricated sliding interface for scraping the crud off. This step took maybe 15 minutes, finished up with rubbing with a cloth wet with paint thinner.

All clean, and no scratches.

------------------

On the decal subject: On previous radios and TVs I have restored, I apply the decals between coats of clear finish. The result looks perfect, with not a hint of visibility for the decal film. I have not found it necessary to apply the decal with the clear finish wet. I simply let it dry, and apply the decal using the usual water float method with a tweezer. After the decal dries in place, the next coat of clear finish can be applied. A few coats over the decal with light sanding in between gets rid of any trace of a hump from the thickness of the decal film.

Back to cabinet stripping...

Wow Tom, at this rate you'll likely be done with the set by Christmas! way to go!

Thank you for the decal note, Phil. I will need a set when I eventually have my CT-100 (re-)refinished. It has no decals now.

Been very busy with the cabinet refinishing for past couple weeks. Lots of dents to steam out and/or fill, plywood and veneer repair on the feet, etc.

Anyway, I've got the entire cabinet grain filled and stained, and wanted to confirm that the very bottom of the sides should be substantially darker than the rest of the sides -- everything from the horizontal veneer cut downward (basically the last 3-4 inches at the bottom).

How about the bottom skirt on the front? Should that also be a shade darker than the rest of the front? That was not easy to tell on mine, since the original finish was in quite poor shape at the bottom.

I'll darken the bottom areas further once I know whether that is correct.

I'll be happy to defer to the experts, but my cabinet is a uniform color from top to bottom. Of course, now it has been refinished, but I just looked at cabinet photos in its as-found condition and there's no indication that there was darker toning anywhere near the bottom (or anywhere, period).

As you've probably noticed from examining interior areas protected from sun fade, the original color was rather reddish.

Phil Nelson
Phil's Old Radios
http://antiqueradio.org/index.html

Well, a sample of one, but mine is not noticeably darker at the bottom... In fact, in front, the feet and area between them under the speaker area are slightly redder than the rest of the cabinet.

jr

That's consistent with that area being somewhat shaded from UV exposure. If you disassembled the cabinet and looked at finished edges never exposed to sun, you might be surprised how red they look.

Phil Nelson

That is indeed true, but there may also be some color differences in the base material as well, as the color changes are quite abrupt and on the "seam" lines.

jr

In that case, maybe they were originally somewhat darker and my cabinet was so faded that it all looked the same. I'm working with sample of one, too :)

Phil Nelson

Thanks for the feedback -- sounds like both of yours are uniform, and were thought to be that way originally as well.

Anyone else? Take a look at the first picture in my post at the top of page 7. That's what's making me think the bottom should be darker. In any case, I haven't done anything yet to make the bottom darker, so if the consensus is that it should all be the same, it will save me a step.

Here is an example of what I mean... The piece coming down on the right side is quite brown (almost like walnut to my eye) Below the speaker area Reddish brown, like *most* of the cabinet. Below that more reddish, except the foot is a little more brownish. I hope that it was a little more uniform when new! This set is un-restored (obviously) pretty much "as found" in 1971.

If I may say so, my set has about the nicest original finish of any I've ever seen. The entire surface looks uniform to me. http://tvontheporch.com/images/pictu...11_290x359.jpg

Well, that all looks pretty convincing. I suspect mine may have been modified at some point -- maybe a partial refinish of just the side feet areas or something like that. I'll go with uniform color on the new finish.

Some pretty nice looking CT-100s out there. Thanks for posting!

You may be seeing normal assembly-line variations. The foot is likely a different type of wood than the veneered front. Manufacturers used toner rather than stain because it did a better job of giving an even color on both the expensive veneer and the cheaper structural pieces. (Plus, toning lacquer dried very quickly, unlike stain.) Wood is a natural product, and not every piece of the same type of wood is identical.

Cabinets were made on an assembly line by humans, not robots. On ARF someone posted a video of RCA TV production in the 1950s. In the finishing segment, the cabinets are on a moving conveyor and the lady sprays on lacquer with a hose that looks like it could cover a school bus in a few seconds if she opened the nozzle a little more. It's remarkable what a good job the workers (generally) did under such production pressure. As you probably know from finishing, even a moment's inattention can produce unevenness, and different kinds of wood may still look a little different under a uniform coat, owing to differences in the tightness/depth of the grain and the way it takes the light at different angles. Then you need to factor in the unpredictable effects of UV fading over a period of decades. I have seen a photo of a CT-100 that sat in a sunny store window for years, and its color looked nothing like an original.

Phil Nelson

Indeed! The two sets at the Early Television foundation illustrate this:
http://www.earlytelevision.org/images/2_cabinets.jpg
jr
http://www.earlytelevision.org/rca_ct-100.html

I'm more of an electronic guts type of guy than a cabinet refinisher, but here are cell shots of what I like to think is pretty much a pristine CT-100.

shots 13-12-22 13.15.10 and 13-12-22 13.15.42 taken on the right side of the cabinet clearly show a dark area below the seam. But the dark clearly begins below the seam. The area was illuminated with a 6500 degree K lamp and looks the same by eye as in the photo. Phil is probably on the mark.

shot 13-12-22 13.17.38 is of my operational CT-100; it has an early history of poor storage environments. It too shows a darker lower member although it is harder to tell compared to the other set.

A new observation for me: In both cases it is evident that the grain pattern flows from the veneer side panel to the lower member. Perhaps you can detect it in the marginal cell photos. Did they use the same sheet of veneer to cover the side panel and hardwood frame members? Seems a bit extravagant, but perhaps a quality damn-the-cost practice was invoked because of the status of RCA's first color set?

Pete

Actually, it's a continuous sheet of plywood down the sides all the way to the bottom of the feet. The horizontal line is nothing but a shallow cut through what is otherwise continuous veneer.

OK, so I guess some sets had a darker finish at the bottom, and some didn't. Mine is like Pete's, except that the border between lighter and darker coincides more with the horizontal cut on mine.

Any correlation to build date, mine is fairly late (B80036743)... perhaps they simplified the toning process on the later sets? :scratch2:

jr

Jr. Doubt the build date had anything to do w/the final finish on the CT-100 cabinets. Probably more to do w/the skill of the person applying the toner/lacquer or even the lateness of a shift and a tired employee. Much the same as any mass produced product during the pre automation era & tireless robots of today. Many RCA cabinets & chassis were pulled from the line during final inspection for repair.

Photo courtesy: Dave Arland

-Steve D.

For what it's worth, mine is B8000952, cabinet #797. So that may be a relatively early one, and it has the darker area at the bottom. I decided to go ahead and darken that area again, now that I know it's not likely some kind of modification after manufacturing.

The first two pictures in my post above are of one of the last CT-100's built; the third picture is of one of the first built. So we're all over the place with build dates.

Pete