Homemade Color Wheel TV
 

I have been debating for some time if I was going to post one of my latest projects on this site in fear of all of you thinking I was completely nuts but seeing that there is this new section I figured what the heck.

After seeing a working color wheel TV at Steve McVoy's museum I wondered if I could build one. I have been planning to do this for some time but never thought that they would really work. Here are some pictures of my attempt. I made the color wheel from two thin pieces of Plexiglas with the filters in between. The TV is an old Coronado. The converter chassis I built from plans in a 1956 Radio Electronics magazine. Steve has given me a lot of advise and encouragement but I do not have it working yet. Lately I have been too busy with other things to work on it but hopefully I can get back to it soon.

Steve

Back of the set

color chassis

Thats really cool and a nice custom cabinet. What chassis did the article use. Any possibility of posting the article. Reason I ask is because my father once told the story when around 1955 he bought a color wheel kit and installed it to an RCA 630 chassis. He said he never did get it working but used it for a while wathcing in B&W. Now that he thinks about it there may not have been any color transmissions at the time.

Paul

Right on Dude!
 

SteveK,

Let me be the first here to congratulate you on your enterprise. That is fantastic! My only advice I can think of is to suggest you use a 10FP4 or if a 12" CRT use whatever the aluminized one is as you will really appreciate the extra brightness due to the terrific loss through the filter wheel.

I was thinking also of doing such a project but want to make mine with the RGB filters on a drum where the CRT is inside the drum. I figure I can get a larger display in a smaller cabinet that way, and the picture can be centered in the cabinet like a normal set.

It looks like you are very close to getting this project operational. Please keep us posted!

RPM's.....
 

I've been to Steve K's home and seen this little beauty in operation. It's a really slick professional job. I think with just a few adjustments Steve will have a glorious color picture. That color wheel really gets going!

this is the first time i have ever seen such a device!

Ive never really browsed these forums but this is quite intersting. Im guessing that the color wheel spins really fast therefore giving color picture. although i cant understand how it works. Intersting though!

Steve D: Thank you for the kind words. If I ever get it working you will need to be my witness here on the forum.

Haoleb: The wheel spins at 600 RPM. The NTSC color signal is converted into a field-sequential signal thus providing the red info, then green, then blue.

Rob: I am using a 10FP4. The wheel does cut down on the brightness but it is still bright enough to watch with normal room lighting. I did not use that tube by design though, it was the only one I had on hand! A color drum set would be interesting but if you used an old CRT it would have to be fairly big. Also mounting the CRT assembly and the drum assembly would be a challenge. However, I too can have the picture in the middle of the cabinet, all I need to do is stick a big extention out on the left side to hold the radio and phonograph!

Paul: The magazine article was the same as the Colordaptor that was available at the time. One could buy the wheel and coils but I don't think that the entire thing was available in kit form although I could be wrong. If you'd like I can mail you a copy of the article. I'm not sure of the legalities of posting it here.

Steve

Way to go Steve K! You know, I have lately had a wild idea to, in my spare time (HAH!) to use one of those 24 inch steel Dumont CRT's and a large color wheel, along with some kinda converter to build a HI DEF set. Certainly the scan could be run at any shape, size and line count you want. Anybody want to tackle THAT one??:D
Marlin

Big Wheel in Mo.
 

Marlin,
One of the reasons sequential color tv was impractical was that with increased screen size the wheel also had to increase in diameter, Your proposed 24" screen set would require an extremely large color wheel. In fact if that baby with its aircraft powered motor got loose, Fenton, Mo. would have a very long ditch thru it starting at your house.:(

you could cut slots in ceiling and floor for the wheel!
put some blades on it and use it to replace the hvac blower!:D

"..if that baby with its aircraft powered motor got loose, Fenton, Mo. would have a very long ditch thru it starting at your house..."
My mom always did say I would wind up diggin' ditches!;)
Marlin

HI Steve,
Thanks for the article. I emailed it to my father and here is an excerpt of his reply.

Interesting he mentions a 5 inch tube. He's probablly thinking about one of my 5AXP4 or 8XP4 test tubes. Since I thought about the possibility of a standard CRT not being bright enough I thought using an early projection crt directly viewed would give the brightness.

Take care,

Paul

Update
 

I thought that I would post an update on my color wheel project. It does not work yet but I think that I am getting closer. The converter chassis has been aligned. I now have to realign the TV chassis to pass the color signal through the video.

I continued to work on the cabinet as can be seen in the picture. I figured that if I never get it to work it will at least it will look better when it's sitting in the dump!

Looking good Steve! How can you talk about that ending up in a dump??????? Will it to the museum so that it'll be preserved.

Anthony

The first time I've seen this thread. A great looking cabinet, and the whole thing looks first rate. Worlds better than stuff I try to make! You are going to have something special when you are all done, something to be proud of.

Steve,
Thanks for the update and the picture. That looks like a factory prototype set. Very professional job.

Amazingly good job! I see so much hack work as a mechanic, it's really nice to see somebody do a quality job. It does look like a factory prototype... Not that far from the Zenith color set that was in the early color forum a while back.

I understand that Zenith built mechanical color chassis under contact for CBS... True?

Hey Guys:

Thanks for the compliments on my tv project. Now if I only get it to work.

Anthony- I'm not sure if a museum would want it as it is not real. Well, it's real but not an old one. With all that work I put into it I would not take it to the dump but based on the look of the screen surround I may turn it into a Bendix front-loader! (thanks to Steve D for that suggestion).

Steve

how is the spinning wheel??
 

Steve,

I am always impressed by the ingenuity of you guys!!!

Not to mention the skill and craftsmanship!

So how is the project going?

Is the aim to have an NTSC colour displaying through a color wheel or is the NTSC signal converted to a CBS field sequential standard and effectively being displayed on a CBS color standrd TV ie are you building an NTSC set or a CBS FS set?

Meanwhile .....do you take orders for a 625 line Pal version!

LOL

chris

Instead of switching between R G and B, you might just dynamically switch the phase shift (tint knob) of the 3.58 oscillator fed to a chroma demodulator to get R-Y, B-Y or G-Y, and then combine those with Y to get R G and B to feed to the CRT. You only need one color at a time, so a single chroma demodulator would be enough.

Another approach on syncing the wheel and switches:
With NTSC as the source, and the fact that an NTSC color set chassis would have R G and B avaliable at all times, you could just let the wheel free run and have an optocoupler or such on the wheel to sense its position and drive the R G B selection switch off that. You'd also need to know where the raster scan of the CRT is when the wheel changes color over its current position. Mainly in the vertical dimension.

Expect to see some funky motion artifacts with a color wheel display. A white moving object on a dark background will show as a trail of RGBRGBRGB ghosts.

Chris:

Thank you for the compliments. I have not had a lot of time lately to work on it as my semester recently ended and I have been busy trying to get my grading finished. I turned in my grades today but will be going out of town for a few weeks. I received much encouragement on this project at the ETF convention and look forward to getting back to it.

I realize that there are many approaches to providing a color picture using a color wheel but I am attempting to do it as described in a 1956 article. That method is to take the NTSC signal and convert it to field sequential. I have seen this circuit work at Steve McVoy's museum and witnessed the excellent picture that it can produce. At this point I would be happy with a lousy color picture!

If I get this thing to work I will try that 625 line PAL version but Chris, you will have to ship me the B+W television!

Steve

Hi Steve K. Good onya, glad to see people having a crack at the experimental methods of the early years of colour television :D !!! Best of luck getting it crankin' , hope your set will give a nice colour picture. Plus I agree with everyone else who said this, it looks like a very professional job :D !

Cheers
Troy

if CBS had succeeded??/
 

This brings the question if the CBS standard had taken off I can only assume pretty quickly all electronic sets would have been available and by now that would be all there was ....but would it have seen cheaper sets sooner?????

But how do you adjust color saturation and what about phase errror??? mmmm....

And Steve, well ...even a copy of the NTSC circuitry would get me going ...I would consult my electronics engineer mate to build it here ....:) He build me all sorts of electro-mechanical devices.

But I doubt too many of us could construct such a beautiful cabinet!

If it comes to that, I'd just install a modern small screen color set rather than throw it out. :D That cabinet looks excellent.

Colordaptor in October-November 1967 edition of Radio-TV Experimenter
 

Steve K, that's a superb job! I'm sure your perseverance will pay off and you'll get it working. The reward of receiving present-day colour television pictures using historical technology and the satisfaction of knowing you built the equipment yourself will make all the time and effort spent well worthwhile. It's great to see someone experimenting with these old techniques.

In 1981 I found an article by Al Sicherman titled "Add Color to Any TV Set" in an old October-November 1967 edition of Radio-TV Experimenter that had been stored in my father's workshop for years. This described how a rotating tri-colour filter wheel could be placed in front of an ordinary black-and-white television set and with some additional circuitry it would produce true colour pictures. I was fascinated this could actually work and so had to try it.

The article explained that in 1946 CBS had demonstrated a colour television system using a tri-colour filter wheel. However, rapid advances thereafter in development of the tri-colour kinescope tube made the colour wheel practically obsolete, except for a kit that was developed by a small manufacturer in California. At the time of printing, plans and an optional kit for a converter, the Colordaptor, were available from De Var Electronics Co., Menlo Park, California 94025. The full kit cost about $100.

A description of how the converter worked, with photographs and a block diagram, were presented in the magazine article. Unfortunately there was no schematic circuit diagram. Since the converter was designed for NTSC, whereas in New Zealand the colour television system is PAL, I would have to modify it anyway. With assistance from some schematic diagrams for a mostly solid-state PAL colour television receiver construction project published in Wireless World magazine in the late 1960s, I set about building modules for a PAL version of the colour converter. The prototype ended up being a transistor/valve (electron tube) hybrid.

The old black-and-white television set I used had an approximately 48 cm rectangular screen, so the colour filter wheel ended up being a bit over a metre in diameter! A 125-W induction motor with a toothed-belt reduction drive rotated the wheel at 500 r/min (50 Hz field rate interleaved to give 25 frames/second). That prompted me to come up with the idea of what I thought at the time was a novel solution for a potentially smaller rotating filter assembly: a drum. This would also enable the borders between filters to be parallel with the scanned lines throughout rotation, avoiding the wheel's requirement for spiral borders, which are a compromise. However, a drum's construction and balancing would be more difficult and its mounting would have to be much sturdier. Furthermore, it wouldn't easily retrofit a television set already in a cabinet, so I didn't pursue it.

The project progressed to the point of getting the chroma circuits and the tri-stable switch (based on a counter IC) working with input from a simple signal generator. I managed to get the system to display rasters of red, green, blue, magenta, yellow, cyan and white. I recall that primary colours flickered quite noticeably (16.7 Hz), exacerbated by the lower field-scan frequency.

I didn't finalize a sync' circuit design for locking the colour wheel's rotation to the tri-stable switch, so for those trials I had to constantly adjust a rheostat in series with the motor. Induction motors generally don't respond well to that simple method of speed control but it was a mystery to me what technique had been used in the Colordaptor to control that type of motor. I thought it might be possible to use a phase-controlled triac but never got as far as trying it. Just recently I learned that one of the original methods involved a saturable inductor in series with the motor. So although it's not the ideal way to regulate the speed of an induction motor, it seems that varying the average current might indeed be an effective enough and valid approach for the fine control required to synchronize the colour wheel.

Unfortunately I never reached the stage of successfully extracting the chroma information from the old black-and-white set and sending it to the chroma decoder, so I didn't get the system fully working.

Steve, your colour-wheel television has inspired me to consider revisiting my old project, though it would be with a slightly different approach now: entirely solid-state (the converter at least) and a smaller screen, wheel (or drum) and motor.

I still have that edition of Radio-TV Experimenter. Until I found this thread I thought the Colordaptor emerged in 1967. It was a surprise to learn that Radio Electronics published the idea in 1956. It would be very interesting to see that article, especially to resolve the mystery and conjecture in my mind after all these years about how an actual original circuit would have implemented certain concepts described in the Radio-TV Experimenter overview.

Hi John, welcome to the forum and thanks for the interesting post! Do you have an address for that company in Menlo Park? That's only about 25 miles from me and I'll try and research it for you.

Anthony

Hi John:

Welcome to the forum and thank you for the compliments on my colour wheel set. The 1956 article that I am using is the Colordaptor circuit from Menlo Park. I also have the updated info from them that they sent out in the early 60s. I believe that the address for Colordaptor is actually a private residence and not a factory or big company as one would expect.

I can send you a copy of that original article if you would like but it would have to wait a few weeks as I am currently out of town. Ceebee23, another forum member, (in Australia) is also considering building a color wheel set. We will have to have a race to see who can get one working first! I think that I will need that type of motivation to ever get mine working. Lately I have not had the time to work on mine as I am busy restoring several other old TVs.

Steve

Like everyone else, Steve, I'd say it looks pretty impressive so far! Wow!

It's funny; I was just thinking about this old project thread the other day when I received an email from someone about the "Land effect" in color vision. Here's a page with a very nice example of the Land effect:
http://land.t-a-y-l-o-r.com/
Notice how the cheeseburger picture has the illusion of being in full color, despite being produced from only white and red light.

I always thought it somewhat surprising that there haven't been many "practical" uses found for the Land Effect-- one of the few I've ever seen suggested was an old PopSci article which described a B&W-to-color TV converter which was being developed by a company called "Spectrac" located in Ontario. Unlike the "usual" tri-color filter wheel designs, this one only uses two colors-- red and cyan. (!) One neat side-effect of only using two colors is that it appears from the description that no scan converter was necessary to create a field-sequential signal-- the usual interlaced field pairs are (apparently) simply turned into "red" and "cyan" fields. Also, rather than a color wheel or drum, the proposed Spectrac design used a slow-moving endless plastic belt with thin diagonal black stripes, with a stationary filter screen in the middle with thin vertical stripes of red and cyan. This would produce alternating fields of red and cyan if synced with the CRT's electron beam. (the black stripes form a diamond pattern that alternately 'hides' one line of the red or cyan stripes)

Anyway, I just dug up the magazine in question-- it's the December 1971 issue of _Popular Science_. Attached is a picture (probably 'simulated') of it in action.

I would assume this product never hit the market; has anyone here ever actually seen one of these..?

Hi all.


Anthony,

The address for De Var Electronics Co. in the Radio-TV Experimenter article about the Colordaptor appeared exactly as in my previous posting; no street or road mentioned. I hunted through the rest of the magazine looking for advertisements for the company, but couldn't find any in that issue. I suppose readers at the time had to look them up in the telephone book.


Steve K,

So, it appears that Colordaptor pre-dates the 1967 Radio-TV Experimenter article by over a decade. That must take it back to within a few years of the commencement of NTSC public broadcasting. I wonder how long the plans and/or kits were marketed after 1967.

If I have another go at making a colour-wheel TV set, my progress won't be quick either, as I have a lot of other projects too.

Over the years I disassembled my converter modules, though I still have some parts like the motor and the skeleton of the wheel. It was only a prototype anyway, so was made in a very temporary manner. The filter material I used was just red-, green- and blue-coloured cellophane. Amazingly, when new, the colours and saturation of the dyes was incredibly close to the ideal (Kodak Wratten Nos. 26, 58 & 47), but faded over a few months in ordinary daylight. What filter material did you sandwich between the acrylic (Plexiglas/Perspex) sheets of your wheel? It would be interesting to find out if red-, green- and blue-coloured acrylic sheet corresponds to the correct primary colours.

When you get a chance, I certainly would be very interested in viewing a copy of the original article. I'd love to see how they implemented the tri-stable switch and the motor control circuit using valves/tubes.

If anyone is interested, I could post a summary of how the Colordaptor worked, based on the overview in the Radio-TV Experimenter article and also list what needs to be done to convert the high-level design to PAL.

If he were to do that, I'd have him build a circuit that would sequentially blank 2 of the 3 guns in the color CRT so as to rotate thru RGBRGBRGB. Take the vertical sync pulse from the vertical circuits and build a divide by 3 digital circuit using TTL chips. Use a digital decode chip to convert from the binary divide down count to 3 outputs, only one enabled at a time. This vertical scan output 1 is enabled, 2 and 3 disabled. Next vertical scan 2 is enabled and 1 and 3 disabled. then next scan 3 is enabled and 1 and 2 disabled. Lines 1, 2, and 3 control blanker circuits tied to the R, G and B signal lines going to the video CRT driver amps that in turn drive the CRT. You will need to turn up the contrast to make up for the fact that each color phosper is "on" for 1/3 the original time.

This should give you a good simulation of what a color wheel sequential set would have looked like.

how do you......
 

with a field sequential set (or for that matter a B/W set using a a color wheel adaptor)....how do you adjust color saturation ?? brightness and contrast are obvious...phase ..well that too ..but saturation ....or is that effectively fixed?

chris :)

This issue is white balance rather than saturation. In the CBS system a color balance device was instaled with each camera. The three colors were extracted. Level controls allowed the operator to achieve white balance, then the colors were put back in sequential order.

Since all receivers used the same color filters and the same CRT phosphor, white balance on the receiver was automatic. However, we noticed a noticable difference in balance on the two CBS sets we demonstrated last year. This was due to ageing of the filter material. In fact, the filters on both sets had been replaced, and the colors were different from each other. Darryl adjusted the saturation of the colors within his converter to acheive the best white balance on one of the sets (the other, the Gray monitor, had a yellowish tint when this was done). Eventually we will use the same filter material for both wheels.

but just how good was it???
 

having read so much about the CBS system ...and the infamous spinning wheels....I have always wondered just how good or ...if you prefer, bad was the system in operation....

having seen the stills of the field sequential sets on the ETF site...which are in themselves amazing ...the question remains what is a real moving image really like on this system ...was the flicker as bad as you would expect ....and what about fast moving objects???

mmmmm...one day I will have take myself to OH. and find out...(may I will bring Troy ...the other Aussie on this board with me ..!)

:D

The picture is amazingly good, especially when compared to the RCA sets of 1954-65. Colors are very sharp, no fuzzy reds, good flesh tones. And, I haven't seen any flicker. I think the flicker problem was with the early CBS systems which used 20 fps rather than 24.

My Col-R-Tel
 

I have my Col-R-Tel up and running on a Philco 12" although the CRT is not great. The picture is a very rich CT100-like color and can be saturated right off the dial. And full hue control to boot.

There is a noticable flicker that dulls down the more you watch it, but the most objectionable thing is the artifacts in the picture from the conversion process. Crawling stuff everywhere. And the resolution drops like a stone. Small graphics are tough to read.

Now if anyone has a spare 12KP4, I would like to buy it and be able to get a better picture so I could post some photos.

Dave

Below is a simulation of what I think a sequential color image would look like with a color wheel. The animated GIF is supposed to cycle from color to color in 1/100 sec, but may be slower on old computers.

Picture is a tiger in the green grass.

CBS Color wheels to go
 

Here's a British site for you color wheel do it your selfers.




http://www.sptv.demon.co.uk/ :D

On the picture of the tiger it is really pulsating on my computer. The real color wheel TV looks better...the color is pretty steady.

Re: how do you......
 

Chris,

With a colour wheel converter on a monochrome set, saturation is adjusted by varying the gain of the chroma amplifier (i.e. the "Colour" control), exactly the same as a conventional tri-colour CRT set. If you turn the gain of the chroma amplifier all the way down, the colour-difference signals disappear and only the luminance modulates the CRT (the same for all three filter colours), so a black and white image results.