Building an Antique Televisor

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Building an Antique Televisor

Postby Lawnboy » Tue Dec 08, 2020 10:00 am

I'm in the planning stages of a new project-- building an authentic-looking Televisor (sans case) that is relatively easy to construct and with a design that others can copy, based on the instructions given in Television for the Amateur Constructor. The motor will be a dual shaft universal motor just like the original, powered by the mains through a resistor or triac dimmer, and the lamp a series of LEDs just like a modern monitor. The trickiest part will be recreating the sync equipment. I would like to keep the toothed wheel, the difference being that the gear will be fed only by the amplified sync pulse extracted from the video signal. The sync assembly will not rotate. For framing, the separated sync pulse will be delayed electronically, using a circuit based on the one designed by Peter Smith for the transatlantic tests in 2003. However, I re-read Peter's analysis of the Baird sync setup in Vol 38 No 1 and am now wondering if this is feasible. I know very little about designing an amplifier to feed a coil in this way, and it now seems just using a brief pulse will be inadequate. Any thoughts on this, or who I should talk to?
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Re: Building an Antique Televisor

Postby Steve Anderson » Tue Dec 08, 2020 7:07 pm

Lawnboy wrote: ...powered by the mains through a resistor or triac dimmer,

Be careful there, a triac based dimmer is generally designed for resistive loads, (light bulbs, shower heaters and the like) not inductive loads. It's best to try and copy a variable-speed hand-drill controller which is designed for inductive loads (any sort of motor)...or even fluorescent light dimmers. The sharp switch-on partway though the input sine-wave can impart kV of voltage into an inductive load..and zap the triac..a 'snubber' network may be in order, but I'm no expert here...

The large reostat/resistor is easy to understand but it doesn't have the 'firmness' of a triac switched supply, depending on the numbers it might become more of a current-source rather than a voltage-source. Not there's any real difference between the two, just how are you gong to arrange the feedback path?

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Re: Building an Antique Televisor

Postby Lawnboy » Wed Dec 09, 2020 9:37 am

That's an interesting point, Steve. My father had a mini lathe powered by a universal motor with a simple knob speed control. At low speeds you could definitely hear the buzz of the mains, so I assumed it was a regular dimmer. I'll look into that.
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Re: Building an Antique Televisor

Postby Harry Dalek » Wed Dec 09, 2020 5:33 pm

Saturable reactor (magnetic Amplifier) does the trick ,i don't know why its not used much these days ,you can control HV safely and very simple .
I found you don't even need the DC replacing it with resistance on the secondary of you controlling transformer to a point but make sure it doesn't over heat (use high wattage resistor or don't get to the point where you short your pot add a low resistor in series or globe ) will do the trick as well ...a globe in series with the resistance will help as well dissipating the voltage ,the transformer is still outputing AC on the secondary which your using as the control device . a tiny AC transformer can control a large device same as what i am using on my phonoVison to power the tiny geared motors amazingly useful Transformer when you have a need to vary a larger transformer with to high a voltage to a lower voltage , should control a motor but i have never tried that have to admit .

youtu.be/ci9AI5KuToM
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Re: Building an Antique Televisor

Postby Steve Anderson » Wed Dec 09, 2020 6:13 pm

Harry Dalek wrote:Saturable reactor. I don't know why its not used much these days..

It is still used in radar for generating short pulse widths into a transformer to power the Magnetron. A pulse voltage is applied to a transformer that also has a saturable inductor in parallel with the primary, At first all is well, the tranny does its job and powers the magnetron with a few kW, after a while (depending on the range required) the parallel inductor saturates and shuts off the current to the transformer. It is a bit of a 'black art' though.

Even in marine applications you want a resolution of 5m or less, that's a very short time when you're trying to berth a huge container ship or cruise liner. Speed of light comes into serious play here.... 3.33ns/m. when you're trying to land an aircraft in fog, 10m of altitude = 66.6 ns there and back...Not a big deal today, but can you imagine what it was like in the 50s in London with all the pollution of surrounding housing burning coal? Here I'm talking about ground proximity warnings...

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Re: Building an Antique Televisor

Postby Harry Dalek » Wed Dec 09, 2020 7:51 pm

Steve Anderson wrote:
Harry Dalek wrote:Saturable reactor. I don't know why its not used much these days..

It is still used in radar for generating short pulse widths into a transformer to power the Magnetron. A pulse voltage is applied to a transformer that also has a saturable inductor in parallel with the primary, At first all is well, the tranny does its job and powers the magnetron with a few kW, after a while (depending on the range required) the parallel inductor saturates and shuts off the current to the transformer. It is a bit of a 'black art' though.

Even in marine applications you want a resolution of 5m or less, that's a very short time when you're trying to berth a huge container ship or cruise liner. Speed of light comes into serious play here.... 3.33ns/m. when you're trying to land an aircraft in fog, 10m of altitude = 66.6 ns there and back...Not a big deal today, but can you imagine what it was like in the 50s in London with all the pollution of surrounding housing burning coal? Here I'm talking about ground proximity warnings...

Steve A.


It is a learning curve for sure what works what doesn't ( here you must experiment )what i found if the controlling transformer is small smaller the better transformers the same size funny enough i never gave as good results ...
i can see Steve the control transformer as a switch would work very well and simple ! amazing what you can do with a transformer .
The electromagnetic spectrum has no theoretical limit at either end. If all the mass/energy in the Universe is considered a 'limit', then that would be the only real theoretical limit to the maximum frequency attainable.
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Re: Building an Antique Televisor

Postby Lawnboy » Thu Dec 10, 2020 12:01 pm

Harry Dalek wrote:Saturable reactor (magnetic Amplifier) does the trick ,i don't know why its not used much these days ,you can control HV safely and very simple .

I'd never heard of something like that before. Very interesting video clip, Harry.
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Re: Building an Antique Televisor

Postby Harry Dalek » Thu Dec 10, 2020 2:33 pm

Lawnboy wrote:
Harry Dalek wrote:Saturable reactor (magnetic Amplifier) does the trick ,i don't know why its not used much these days ,you can control HV safely and very simple .

I'd never heard of something like that before. Very interesting video clip, Harry.


Used in the V2 Rockets as well i recall ; 0 ) pretty much how they used to control high voltages with out electronics .
Experiment put 2 mains AC transformers primaries in series the one you want to adjust voltage measure the voltage on the secondary .. the secondary of the controlling transformer short it see the result .
I used the idea to control the voltage for a CRT i needed to control a transformer so the later outputting HV DC was with in range ..i used 2 resistors a few watts across the controlling transformer secondary to get the correct voltage out of the working HV transformer ...its very safe( say you put low watt resistors) in and they over heated and burnt out all that happens is the voltage out of the main transformer just drops ....win win really

As i mentioned the controlling transformer seems to work better if its a very tiny mains transformer as i recall as in giving a better voltage range how i used it ...might give better results as in the video with DC control. i have used that idea in the past as well but i went simple :wink:
The electromagnetic spectrum has no theoretical limit at either end. If all the mass/energy in the Universe is considered a 'limit', then that would be the only real theoretical limit to the maximum frequency attainable.
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