solid state col r tel or colordaptor

[old_tv_nut]

Originally Posted by cbenham

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

The CBS/Motorola "EVR" film video player in 1970 used an induction motor with a simple SCR control circuit, so (IIRC), it actually had pulsed DC going to the motor. At first it used a shaded-pole motor, but that operated so poorly that I convinced them to spend the extra money for a capacitor-run motor. The pulsed DC was not very kind to the motor, resulting in low efficiency and lots of wasted heat.

The film had sync windows down the middle that were sensed by a fiber light pipe source shining through onto a phototransistor that triggered the SCR, so the SCR itself was the phase detector between the trigger pulse and the phase of the AC line.

[vintagecollect]

hello cbenham,

pielock did a great job on his colorwheel. The motor used looks rather small, the setup is very efficient. I'm hoping to hear from him sometime soon.

[mbates14]

I built my colorwheel motor control circuit using a microprocessor.

It takes a long time for the disc to lock because of the "flywheel effect" but it eventually locks, maybe if i apply more braking force against the motor/disc, it will lock faster and suppress "hunting"

But the microprocessor controlled servo that i used, seems to be rock solid once it locks in. works with various types of motors and setups I have tried. I havent messed with it in a couple of years though, other than i got a new hub from cliff. But i scratched the wheel so bad from tucking it away and pulling it back out, that its almost unwatchable. Which reminds me, i need to send his hub back to him, as i had his copied and recessed to hold magnets for the timing pickup.

[vintagecollect]

I'm getting some ideas for the motor speed control, A PWM type for DC motors, A larger DC12v motor for a smaller disc? The hobby shop sells a pricey kit, online has motor control already assembled at a better price. Has anyone here done an opto phase control to synce wheel to picture RGB correctly? any idease please.

[old_tv_nut]

Mechanical TV hobbyists make decent servos for the wheel speed when the optical detection pulses are at 400 Hz. I did one for my mechanical TV.


Besides the wheel inertia, however, it is much more difficult to make a decent servo for something at the low rate of 20 Hz that you have with the Col-R-Tel. I never was very successful with getting the 15 Hz mechanical TV wheel to phase up automatically, event though the speed was well controlled.

For what it's worth, the servo development is here:
http://www.bretl.com/mechtvprogress2...o%20design.htm

I think a multiple-pulse-per-rev servo for speed with an added once-per-red-field phase detector of some kind might be worth a try.

[vintagecollect]

pwm motor controls are common, it looks pielock uses a foreign pre made jobber. The motor looks 12v w/ a high torque gear box. No reply yet from him. Looking to get info on motor at least, is his wheel watchable w/out a phase lock? Waiting for feedback.

hey tv nut,
WAS you mech set watchable w/out sync? did it go out of sync a lot? Is a color wheel viewable w/out red sync pulse, HOW often would it go out of sync?

[old_tv_nut]

Originally Posted by vintagecollect

pwm motor controls are common, it looks pielock uses a foreign pre made jobber. The motor looks 12v w/ a high torque gear box. No reply yet from him. Looking to get info on motor at least, is his wheel watchable w/out a phase lock? Waiting for feedback.

hey tv nut,
WAS you mech set watchable w/out sync? did it go out of sync a lot? Is a color wheel viewable w/out red sync pulse, HOW often would it go out of sync?

Mech TV practically impossible to view without sync. Sort of "look, there's a picture - oops" as you constantly adjust. Peter Yanczer has shown some systems where camera and monitor both used synchronous motors running from the AC line. These were not perfectly stable, but constantly hunted back and forth a bit. The servo does a much better job.

For Col-R-Tel, the hunting from a synchronous motor would be tolerable, I think, but a synchronous motor (60 Hz line) would have a different problem because vertical is 59.94 Hz, so the phasing would continuously drift over about a 17-second period.

[vintagecollect]

Has ANYONE used the original 2 tube setup for motor sync using AC motor w new ss adapter??? I figure the most expensive part to build circuit is power xfrmer unless someone has a junk box w/ spare power transformers. HOW WOULD someone use red signal to original colodapter sync circuit?? Would a pre amp circuit be needed. I have a clean copy of schematic if someone wants this in good detail. Any ideas

[cbenham]

Originally Posted by mbates14

I built my colorwheel motor control circuit using a microprocessor.Which reminds me, i need to send his hub back to him, as i had his copied and recessed to hold magnets for the timing pickup.

That's a great idea! I never thought of embedding magnets in the hub.
Thanks,
Cliff

[cbenham]

Originally Posted by old_tv_nut

I think a multiple-pulse-per-rev servo for speed with an added once-per-red-field phase detector of some kind might be worth a try.

I tried two sets of pole pieces and pickups early on in the CBS wheel test bed set, 48 red field and 144 all field pulses.

The only immediate change was the fairly loud 144 Hz whirring sound as the pole pieces passed the pickup!

I think it would have worked except I blundered the 144 pickup and shattered the disk edge where the 6 pole pieces had been.

There are still more schemes to try as soon as I get time.

Cliff

[cbenham]

Originally Posted by vintagecollect

Has ANYONE used the original 2 tube setup for motor sync using AC motor w new ss adapter??? I figure the most expensive part to build circuit is power xfrmer unless someone has a junk box w/ spare power transformers. HOW WOULD someone use red signal to original colodapter sync circuit?? Would a pre amp circuit be needed. I have a clean copy of schematic if someone wants this in good detail. Any ideas

I've breadboarded several different Colordaptor Servo and TRITCH circuits and adapted them to do the color switching and wheel control for a Col-R-Tel disk and chassis, where the original printed circuit switch and brush system had been destroyed.

While it worked, it was very iffy and not very stable. The wheel would lose sync when the air conditioner started. A big, hot, heavy SOLA constant voltage sinusoidal transformer makes it work OK.

By the way, the TRITCH circuit is very critical to make work. The hardest part is to find the three equal 560K grid return resistors. They don't need to be *Exactly* 560K but they do need to be precisely *EQUAL* in value.

The Colordaptor system uses an audio output transformer to control the motor speed. I've also substituted a vertical output transformer [the 4 lead type, not a 3 wire autoformer] and it worked about the same as I described above.

The only power needed for the Colordaptor servo is a few mils of plate B+ for the 12AT7.

The 6AQ5 doesn't actually draw current from the power supply. It is configured as a half wave grid controlled rectifier. The harder it conducts, the lower the voltage drop across the secondary of the transformer and the faster the motor goes.

HINT: place a 1000 volt full wave bridge rectifier between the transformer primary and it's connections to the 6AQ5 Plate and Cathode. Doing this changes it to a full wave grid controlled rectifier. This works better than the original halfwave version.

As for detecting the red field pulse coming from Darryl's converter, I designed
a transistorized version of the original tube type red pulse detector that's in the Gray Research CBS monitor at ETF.

I built two of these for the CBS sets I displayed at the ETF Convention last year.

The red field pulse is in the same place in the sync signal in both of Darryl's converters, the CBS and the NTSC.

While I've not built one to work with the NTSC converter YET, I'm about to do so because I have a project that needs one.

At this point the only difference I think I'll find is the need to retune the detector tank circuit from the CBS frequency of 58.320 KHz to the NTSC frequency of 31.462 KHz.

The detected red field pulse is the signal that would feed the Colordaptor servo circuit, and be compared to the wheel pulse in the 12AT7 controlling the motor speed through the 6AQ5 and the output transformer.

More as time allows...

Film@Eleven.

Cliff

[cbenham]

Originally Posted by cbenham

The detected red field pulse is the signal that would feed the Colordaptor servo circuit, and be compared to the wheel pulse in the 12AT7 controlling the motor speed through the 6AQ5 and the output transformer. Cliff

Attached is .jpg of the Colordaptor Schematic. http://www.videokarma.org/attachment...1&d=1306567041

[vintagecollect]

thanks mbates and cbenham for input.

This post was created in hopes of getting info to make the aurora designs converter easier to setup completely as a color wheel. The engineer did an awesome job of improving over old circuits to be more reliable. I see several posts w/ scattered info on how motor control and sync was done, BUT none in great detail to recreate any one setup easily. I could see an interest spurring if both circuits are done here for sharing.While some have the equipment and tech level to reverse engineer both circuits, known good circuits would benefit someone wanting more of a plug and play approach, to widen the interest in these units.


Any b/w tv w/ enough brightness could be colorized. Saving a few more b/w vintage sets from the trash. easier to move, store, etc. Color wheels have always been rare and few survive. Easier to find a place for a larger color wheel tabletop tv than a color console, etc.

[benman94]

The Colordaptor schematic isn't available for download. Would someone mind reuploading it? I'm very interested in what the differences between the Col R Tel and the Colordaptor are... One would assume that they would be nearly identical besides a chroma pickup point and the delay line.

[cbenham]

Originally Posted by benman94

The Colordaptor schematic isn't available for download. Would someone mind reuploading it? I'm very interested in what the differences between the Col R Tel and the Colordaptor are... One would assume that they would be nearly identical besides a chroma pickup point and the delay line.

Col-R-Tel was a commercially made unit, ready to connect to your B&W TV.
That is one in my avatar.
Colordaptor was a magazine article with a set of instructions and some major parts available from the designers. This was in 1956.

P.M. me and I'll email you all the info I have on both types.

As I've said before, the color electronics part is easy. The wheel part is not.
I have built 5 wheel sets in the last 6 years. The motors are different for each one based on the speed and size of the wheel, and the servo circuitry for each one is also different.
If you build a wheel set, you will see what I mean. The servo circuit is more difficult to make work than the color circuitry is.

Cliff