Mystery Cinema-Television device

[Vintage_RC]

The pictured device has recently come into my possession. Cinema-Television was a company started by Baird in the 1920's and carried on on one form or another until 2012. This particular device has a 1920's or 30's look about it with its Bakelite B4 base.

The question is what is it? The top is flat but not particularly clear, it has a cylindrical outer electrode but the internal electrode is very difficult to see. The third photo shows a view through the top illuminated with a bright torch.

Only two connections are made to the base, my best guess would be a photocell or a neon device.

Does anyone know exactly what it is and what it was used for?

[ms660]

These photo cells also look similar:

http://www.r-type.org/exhib/aab0062.htm

http://www.r-type.org/exhib/acn0002.htm

http://www.r-type.org/exhib/aaa1650.htm

Lawrence.

[Vintage_RC]

Agreed that externally they look similar but the electrode arrangement is different. The only way light could get into the device I have is through the top which is not very clear and there is no obvious target for the light. Having said that I suspect it is some sort of photocell. There is no type number on it but that might have been where part of the label is missing.

[Refugee]

The second link Lawrence posted has got a label stuck over the photo sensitive side.
You would have to pull the label off in order to use it.
I have got a couple that came from the optical sound system on cinema projectors.

[Vintage_RC]

I took a close look at the label region on my device but in this case the cylindrical electrode is continuous with no openings. I managed to get some better photos of the inside by shining a very bright light into the small gap below the cylinder. They only seem to deepen the mystery, there is no evidence of any photo sensitive coating that I can see. Perhaps I should apply some volts through a high value ballast resistor and see if it glows?

[G6Tanuki]

It does look more like it's intended for end-on illumination. I wonder what the black disc in the centre, with what looks like a thinner wire going to its centre in the style of a 'point contact' diode of yore, is about??

I doubt it's intended to glow.

From what I remember, Cinema-Television Ltd [Cintel] were taken over by Rank some time in the 50s and became Rank Cintel.

[McMurdo]

Browsing the cintel brochure, there's an option for 'end view circular ' photocells which I suppose could be an option.

http://www.r-type.org/pdfs/cintel-57.pdf

[lesmw0sec]

Given that the interior looks highly reflective, I am wondering if the light-sensitive area is the bottom of that black disc, with the surroundings acting to concentrate the incoming light?

[PJC58-Hythe]

It's a photocell and you can test it using the circuit in the image below.

Connect the output to a high impedance amplifier with an input stage of around 5M impedance, or an oscilloscope. Then use a white LED fed with a 400Hz Sine or Square wave from a source with enough voltage and current to drive the LED, shine this into the photocell and you will hear the 400Hz signal or see it on the oscilloscope if you are using that method.

[Refugee]

Originally Posted by G6Tanuki

From what I remember, Cinema-Television Ltd [Cintel] were taken over by Rank some time in the 50s and became Rank Cintel.

The two I have got are side view and one has a Rank label so will be later production.
I felt sure that I tested one with an old Japanese meter with a 22 volt battery and got a response.
I tried with a DMM and got a response all be it a bit rough as I was using LED light with a chopper drive.
I was getting readings that were between 200K and 3 Meg.
One of my AVOs with a good 15 volt battery would have got a more stable reading but at least I have proved that there is no need for an exotic test circuit.

[Vintage_RC]

I've got a dual 30V Coutant bench supply so I can easily get 60V for some tests. Regarding the "black disk" in an earlier post it is an illusion due to the strong lighting from underneath. I have no idea what would be the anode or cathode, if I get it wrong would it harm the device?

[Refugee]

The part number on my one with a label is GS16 and there is a data sheet with a pin out.
http://www.r-type.org/exhib/aai0128.htm

[Vintage_RC]

I have had an opportunity to test the device which is indeed a photocell. The pinout turned out to be different to the GS16 and is shown on the attached test circuit. I was surprised at how well it worked at low supply voltages, a current of 5uA was obtained under bright light right down to 30V and it was still responding at 10V. A summary of the test results follows:-

Cinema-television photocell tests

Test circuit "Photocell.jpg" attached

DVM was a Tenma with a 10M I/P resistance
Illumination was darkness or an LED torch held close to the flat face
Supply was a Coutant regulated DC bench supply

V Supply, V Load, I Load, Illumination
75V, 17mV, 0.0034uA, dark
75V, 25V, 5uA, bright
40V, 25V, 5uA, bright
30V, 25V, 5uA, bright
20V, 18V, 3.6uA, bright
10V, 9.5V, 1.9uA, bright