solid state col r tel or colordaptor

[vintagecollect]

Hello,

Has anyone done a solid state col r tel OR colodaptor??

Please let me know, if have schematics and or plans for the sold state version please pm me. Does anyone sell this in a kit form?

[miniman82]

Didn't Cliff do one? There were lots of circuits!

[ChrisW6ATV]

I think on the Antique Radio forum for TVs, there was a big discussion by a man who had built a color wheel and bought an adapter that splits NTSC into sequential color, but I don't think the discussion ever got to a completed, working device. He may have been pretty close, though.

[tubesrule]

vintage:
I make those converters, one of which is for use with the Col-R-Tel. It's not strictly a replacement for the existing electronics, but an improvement over the original. With the original you had to cut into the television for horizontal, vertical and video taps, and start with a tv that had high enough video bandwidth to pass the chroma signal. With the converter, the sequential color video is sent to the tv through RF or line level, so no modification to the tv is required. Because of this you can easily move the color wheel from set to set. All that is required from the Col-R-Tel is the wheel assembly and motor control. If you are ambitious, you can design your own color wheel or drum and motor control like Cliff has done.

Darryl

[vintagecollect]

awesome, tubesrule!

You have done much to help the hobby. Please pm me w/ circuits needed for wheel control, etc. Your avatar is coool! You have a prewar or a reincarnation? Please state converter needed for color wheel and all else needed please. Do you use one of your rigs for the Felix screen shot? Please PM me of low def pre war tv clubs too! Thanks

[tubesrule]

vintage,
The specific converter for this application is the SCRF525M-SC. It was originally created at the request of John Folsom and Cliff Benhem to eliminate the electronics, and especially that nasty commutator in the original Col-R-Tel.

I don't have any specific advice on the mechanics or motor control. Cliff is the resident expert in this area. He has all the numbers for exactly what color filters are required and the motor controls he has used. Cliff is the guy who got the drum set working and donated it to the museum this year.

My avatar is an original RCA publicity picture showing a state of the art (at the time) 60 line mechanical image. I have recreated this on my mechanical sets and actually watched a few shows on them. It's not quite as bad as people might suspect.

Darryl

[vintagecollect]

CAN someone please PM me on any available wheel motor control circuits ss recently done. Post any pis would be great too. HAS ANYBODY hooked one of rigs to a rare prewar set?? You don't have to cut into circuits and modify set, maybe the museum can do this for their next convention in 2012.

[miniman82]

Originally Posted by vintagecollect

HAS ANYBODY hooked one of rigs to a rare prewar set?

It's hard enough getting enough brightness through the colored filters with a modern CRT, a pre-ww one would be an exercise in futility.

You don't have to cut into circuits and modify set, maybe the museum can do this for their next convention in 2012.

Having 4 color wheel sets of various kinds is probably enough...

[cbenham]

Originally Posted by vintagecollect

CAN someone please PM me on any available wheel motor control circuits ss recently done.

I've had to build a different motor servo for each of my five breadboard wheel sets because it is seemingly impossible to build one single circuit that works well for all of them.

This is because each set has a different mechanical configuration, a different motor, and a different size color wheel. All of the mechanical and wind resistance differences translate into very different control characteristics for a servo system to deal with.

I'm using 1750 RPM split-phase capacitor run induction motors of from 1/20 to 1/5 horsepower depending on wheel diameter. The common thread that connects them all is the use of the same type of speed control and adjustment: AC from the 120 volt line drives the control circuit and thus the motor. The control circuit is fairly simple and brute force:

To set the correct range of motor speed a 25 to 50 ohm, 25 watt rheostat is wired in series with the AC source, the motor and the other control element, a saturable reactor transformer arrangement made of two identical 35 volt, 2 amp filament transformers. The 35 volt secondaries are wired in parallel, and the primaries are wired in series but out of phase.

When a DC control voltage from the servo amplifier of from 10 to 40 volts is impressed across the primaries, the transformers saturate and pass the full value of AC voltage on to the wheel motor.

Two position and phase sensor pickups on the wheel provide synchronizing pulses back to the servo amplifier which are internally compared to the red field ID pulse or other synchronizing signal coming from the video source to spin the wheel at the correct speed and phase to display the right colors.

None of the servos I built from scratch ever worked the first time. Each one took lots of testing, measuring voltages, studying waveforms on the 'scope
and sort of working into the 'sweet spot' of the design so the wheel would lock up every time I turned the set on. The CBS wheel servo took several months to make reliable, and I continued for much longer fine tuning it.

Each set I built is a test bed and a bread board, not a finished product and not a complete and tested design that could be turned into a kit of parts like the original Colordaptor.

There are other means of spinning a color wheel.
At least two other VK members who have built mechanical sets have used DC motors and servos built with phase locked loop chips.

Some have used triacs to control motor speed, but I found early on although very convenient, they chop the AC voltage which causes motors to over heat rather quickly.

So far as I know, there is not a motor control device 'kit' available.
As each set I built is different, I built a different servo for each one, no two being alike.

Anyone who builds a color wheel set from scratch will have to build a wheel servo that is unique to his set.

I got ideas for the servos I built by reading VTR repair manuals of the 70s & 80s and studying the circuitry of the Col-R-Tel , Colordaptor and the Jay Stanley Projection wheel set articles in the electronics magazines of the 1950s. These articles
are available online and I will send links or the actual articles to anyone interested.

Please Note: Lots of assembly is required. Lots of effort and lots of frustration
will occur before your wheel will sync up every time.

There are no guarantees, and no warranties. You will become an inventor.

It is one thing to build a circuit to lock the local color oscillator in a TV to the signal from a DVD player, but quite another to precisely balance a 4 lb. plastic color wheel and develop a control circuit to keep it spinning at 599.4 RPM and within about one degree of error per rotation.

Best Luck and remember your mileage will vary.

Cliff

[ohohyodafarted]

Cliff,

Just out of curiosity, has anyone ever played around with superimposing DC onto the AC which supplies the field windings of the AC motor. It is my recolection that if you place DC onto the windings of an AC motor it will act like a magnetic brake. Perhaps, the speed could be controlled by varying a DC component in the field coils of the AC motor. Just a thought, I have no idea if it is even a viable idea.

[rld-tv01]

There are some pictures on James Hawes web site at http://www.hawestv.com/mtv_slides/benhamA.htm

[cbenham]

Originally Posted by ohohyodafarted

Cliff,
Just out of curiosity, has anyone ever played around with superimposing DC onto the AC which supplies the field windings of the AC motor. It is my recolection that if you place DC onto the windings of an AC motor it will act like a magnetic brake. Perhaps, the speed could be controlled by varying a DC component in the field coils of the AC motor. Just a thought, I have no idea if it is even a viable idea.

Hi Bob, it is a viable idea and has been used for dynamic braking of the reel motors of tape recorders by AMPEX and others. I've never seen it done by superimposing the DC on the AC power feeding the motor. The usual method is switching the AC and DC voltages to the motor windings through a relay so only one of the two is applied to the motor at any moment.

The recent post showing the wheel set on Jim Hawes website uses two motors to spin and regulate the wheel speed. There are pictures showing the mechanical configuration. This is the set I showed at ETF in 2006.

The main motor has AC applied through a rheostat and spins the wheel slightly faster than it's synchronous speed. The second motor is coupled to the shaft of the main one and has only a varying DC voltage of about 8 volts applied to it from the servo amplifier. The DC varies across the second motor acting as a dynamic brake to slow the wheel and keep it spinning in sync and in phase with the red field I.D. pulses so the picture is correct.

I used this method to sync this first wheel set I ever built because I had a very difficult time making the saturable reactor servo work. I got the idea for using the second motor from a technical book on VTR and VCR circuitry.

When I get some time, I'll investigate simultaneous application of AC and DC
to a motor and find out if it might work for wheel sets.

I know this will work with a universal motor, one with field coils and a wound rotor with brushes and a commutater, but so far I've used only split phase-capacitor run induction motors in the sets I've built.

The one thing I've never done is to build a set using a DC motor with a phase lock loop chip like the 4046 or a pulse width modulated servo.
I still have much to learn... #;^)

Cliff

[cbenham]

Originally Posted by miniman82

It's hard enough getting enough brightness through the colored filters with a modern CRT, a pre-ww one would be an exercise in futility.

A color wheel unit needs to be built on a TV with an aluminized CRT. The sets
at the ETF Museum all have aluminized CRTs but still the pictures are somewhat dim and best viewed in a darkened room.

The reason for this is that the color filters absorb 90% of the CRT brightness.

A set that produces a bright image of ~150 Ft. Lamberts only has a 15 Ft. Lambert image when a color wheel is spinning on it.

Projection sets like the RCA 648PTK or a Norelco PT200 are already dim at a brightness of only 15 to 20 Ft. Lamberts. Installing a color wheel on one of these sets would reduce that to around 1 to 2 Ft. Lamberts and require viewing in a totally darkened room.

Still, several people have done this in the past and watched beautiful color in the dark.

Cliff

[cbenham]

Originally Posted by ChrisW6ATV

I think on the Antique Radio forum for TVs, there was a big discussion by a man who had built a color wheel and bought an adapter that splits NTSC into sequential color, but I don't think the discussion ever got to a completed, working device. He may have been pretty close, though.

I think you mean Pielock. His thread is quite long and he has the test setup to the point where he can take screen shots that look very good.

Here's a link:
http://antiqueradios.com/forums/view...299b1ae46c2828

Good information here about what you will face when building a one-off color wheel set. Not like building a Heathkit or a Dynaco Tube amp at all!

Cliff

[ChrisW6ATV]

Yes, that is the one, Cliff.