Mini version of Scophony - its do-able

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Re: Mini version of Scophony - its do-able

Postby Markd » Wed Mar 17, 2021 2:41 am

What a great project. Look forward to further developments.
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Re: Mini version of Scophony - its do-able

Postby Gregory » Thu Mar 18, 2021 9:05 am

Markd wrote:What a great project. Look forward to further developments.

Thanks Mark, just hope it will work well at the end.

The Sync/restorer PCB is now ready for testing as below. Unfortunately I made big mistake and placed the artwork upside down when exposing the PCB. To correct this for the prototype I had to bend the IC legs up and loaded them upside down. All the other components are loaded as normal.

2020_linescan_top_pcb.jpg
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Re: Mini version of Scophony - its do-able

Postby Steve Anderson » Thu Mar 18, 2021 4:10 pm

Gregory wrote:...I had to bend the IC legs up and loaded them upside down...

Oops, but so easy to do! I suggest adding some text to be etched, say, "Gregory 2021" (without the quotes), or a project name, circuit function, even IC pin-numbers on each corner of the chips, anything that makes it obvious that something isn't quite right...slightly more work, but it saves these glitches...

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Re: Mini version of Scophony - its do-able

Postby Gregory » Sun Apr 04, 2021 7:21 am

Steve Anderson wrote:Oops, but so easy to do! I suggest adding some text to be etched, say, "Gregory 2021" (without the quotes), or a project name, circuit function, even IC pin-numbers on each corner of the chips, anything that makes it obvious that something isn't quite right...slightly more work, but it saves these glitches...

Yes certainly will do this Steve the next time, as I nearly had to scrap the PCB and start again.

Progress has been slow the last fortnight due to family health issues, now resolved. I have to-day tested the temporary line scan motor assembly successfully and now have ready all the files for the main parts of the televisor base designed. With a bit of luck I should be able to cut these tomorrow.

As yet I have not been able to test the sync restorer PCB but hopefully will do this the coming week.
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Re: Mini version of Scophony - its do-able

Postby Gregory » Mon Apr 05, 2021 3:27 am

The parts for the televisor base have now been cut and now ready for assembly.

2021 televisor2 parts.jpg
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For the frame polygon mirror I will be using the 8 sided one I previously made last time but will replace the mirror faces with wider ones which the new televisor requires. The line scan mirror remains the same 15 sided as before. Next step is to assemble the base.

Below shows the rendered 3d Autocad image of what the televisor should eventually look like, with a bit of luck

televisor2 render.jpg
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Re: Mini version of Scophony - its do-able

Postby Gregory » Wed Apr 07, 2021 5:22 am

The televisor base has now been assembled as per photos. Next stage will be to assemble the line scan assembly and test it

televisor base.jpg
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Re: Mini version of Scophony - its do-able

Postby Harry Dalek » Wed Apr 07, 2021 5:27 pm

Good to see its coming together you really had to start from scratch !
Noticed the original system had problems may be why it wasn't used again or just the war and CRT its time was up ,not here ! i will like to she your beauty display !
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1937_Aug_Scophony_TV_Notice (1).jpg
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: Mini version of Scophony - its do-able

Postby Gregory » Fri Apr 09, 2021 7:43 am

Harry Dalek wrote:Good to see its coming together you really had to start from scratch !
Noticed the original system had problems may be why it wasn't used again or just the war and CRT its time was up ,not here ! i will like to she your beauty display !

Thanks for the info Harry, and yes really bad luck BBC transmissions weren't suitable, otherwise scophony would probably has sold a few sets at the exhibition, and perhaps some sets might have survived. Also more bad luck as the war virtually put an end to Scophony and mechanical TV. Although mechanical TV had its limitations I believe it could have been developed a lot further to be reliable and suitable for mass use.

I started the first tests on the finished line scan assembly to-day and results were initially disappointing as the timing belt at the higher line scan frequencies gave excessive vibration and a reduced maximum speed, due to lower available torque from mechanical losses.

I have thus re-designed this using direct drive to the line scan motor, as in my previous design, but refined this further with an additional bearing for the polygon mirror and adjustments on the motor hub mirror mount to ensure the line scan mirror is aligned very accurately.

It now operates very well and smoothly up to a synchronized speed from the stepper motor exceeding 3500 RPM. When I make the line scan start oscillator with suitable ramping, I should know the exact maximum RPM possible, which may be even higher.

For now with the 15 sided mirror this gives a line scan frequency of 875 hz, which at 12.5 frame rate would be good for up to 70 lines. I should have pics for the modified line-scan assembly and televisor to-morrow.

The next in line, when I get time will be the frame scan assembly and final testing of the sync restorer PCB
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Re: Mini version of Scophony - its do-able

Postby Gregory » Sat Apr 10, 2021 7:27 am

2021_linescan_assy.jpg
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The photo shows the line scan assembly with the motor directly coupled to the polygon mirror. At the front of the mirror is an additional bearing to take the load off the motor bearings, as these are just brass bush bearings, and probably will wear with extended use. The polygon mirror is attached to the motor with a flange having 3 adjustable screws to enable precise alignment.

Compared to the previous televisor, the mirror is mounted vertically instead of horizontal, so that it points directly to the frame scan mirror, without the need for the 2 deflection mirrors originally used.

With the stepper drive set to 1/8 micro-stepping and using a function generator, it was possible to ramp the line scan motor frequency with a step pulse rate in excess of 20 kHz (3000 rpm). Using the 15 sided mirror this gives a maximum line scan frequency of 625 hz
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Re: Mini version of Scophony - its do-able

Postby Harry Dalek » Sat Apr 10, 2021 8:55 pm

Looks very nice ! very jealous !
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Re: Mini version of Scophony - its do-able

Postby Gregory » Wed Apr 14, 2021 6:10 am

Harry Dalek wrote:Looks very nice ! very jealous !

Harry I wouldn't be jealous yet - it might never work!

Then nest step is modifying the original frame scan mirror to fit the new televisor, by widening the base spacer and cutting a new wider set of mirror plates, whilst using the existing octagonal side support panels.
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Re: Mini version of Scophony - its do-able

Postby Harry Dalek » Wed Apr 14, 2021 5:08 pm

Gregory wrote:
Harry Dalek wrote:Looks very nice ! very jealous !

Harry I wouldn't be jealous yet - it might never work!

Then nest step is modifying the original frame scan mirror to fit the new televisor, by widening the base spacer and cutting a new wider set of mirror plates, whilst using the existing octagonal side support panels.



Mechanically it is so well constructed Gregory there's no reason for it not to apart from will to do so ,i can see a winner when i see it ! :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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Re: Mini version of Scophony - its do-able

Postby Gregory » Sat Apr 17, 2021 5:50 am

Today I had some time and managed to construct the new frame scan assembly, using some parts from the original unit.

2021_framescan_assy.jpg

The photos show the frame scan mirror installed into the televisor body.

The mechanical side is more ore less complete, except for the alignments of the mirrors and mirror faces.

The next step is to build 2 temporary oscillators using 555 timers with ramping, so that together with the stepper drives the line and frame scan mirrors can be driven to approximately the correct rotation speed. Also I need to construct a simple but safe laser driver to do the initial experiments.

The thought is to try and get some sort of picture, however bad, and then go from there to refine the televisor as much as possible and also include the sync restorer PCB when I can
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Re: Mini version of Scophony - its do-able

Postby Harry Dalek » Sun Apr 18, 2021 8:27 am

Looking very good !
Yes good idea just see how it gos as is , might show a problem or none .
More than likely best to try with a still image testcard at this stage .
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: Mini version of Scophony - its do-able

Postby Gregory » Mon Apr 19, 2021 7:22 am

Schematic of temporary stepper oscillators for the line and frame scan motors. Basically a 555 oscillator with an additional RC timing circuit to slowly ramp up to the required RPM. The frame oscillator should work well without the additional RC ramp, as this operate at around 93 RPM only. The stepper drives will be set to 1/8 step resolution.

temp stepper oscilator.jpg
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