Globe Television project (mechanical) - UK Vintage Radio Repair and Restoration Discussion Forum

rogerdup · 25th Apr 2018, 6:37 pm

Hello Gentlemen,
Some friends ask me to go again on a mechanical TV project. I found on the ETF pages a link to the hawestv.com literature.
The Globe Television Corp. Us midget set made in 1932 described there caught my attention. Only poor photos of this set are available I think. Based on the size of the tubes appearing on the back, I could imagine the average size of the machine that is :64cm high, 45cm width, 30cm depth. A big midget. The nipkow/brillouin scanning disc is 30cm diameter and made for 60 lines.
So, I think to get started with it, but first need to understand how the crater lamp and the lens were acting together to project the 4x5 inches pictures.
If somebody has info about this, I would be very grateful.
No problem to make a similar cabinet, nor for finding the bulb lamps.
Roger

Dave Moll · 25th Apr 2018, 7:53 pm

You might also find this a useful site.

peter_scott · 25th Apr 2018, 8:19 pm

You can get valve list here.
You weren't far off with the dimensions.

http://www.americanradiohistory.com/...32-May-Jun.pdf

Page 103 says that the scanning disc has 60 lenses (not just pin holes).

See also the projector at the foot of page 105 and article on page 108 not mention page 87 and few others.

Peter

peter_scott · 25th Apr 2018, 9:11 pm

1931 Nov/Dec Television News page 338 article on crater tubes.
1932 Television News Sept/Oct page 190 there's an article on crater lamps and the next article is on Lens Disc Design.

Peter

rogerdup · 25th Apr 2018, 9:46 pm

Thanks Dave and Peter. Reading the litterature, this lens scanning disc appear very complicated to make, and I think we wil have not sufficient skill to go through it. Fist difficulty: find 60 lens correct type for this application!
Thanks for reminding me the Radiomuseum source..I got the real sizes
Roger

rogerdup · 26th Apr 2018, 7:58 pm

First step, on the way to build the prototype: the bulb shaped valves.

From left to right:
UP:
Two 24 tetrode RF amplifier
One 80 rectifier
LOW:
27 detector,
24 1st préamplifier,
27 2nd preamplifier
47 power amplifier (the originals 45 not affordable)
47 power amplifier. The p.a. tubes connected in parallel.
To be continued (I think..)

Roger

wd40addict · 27th Apr 2018, 1:03 pm

Interesting it seems to have been at least partially designed by Alan DuMont. Later to get into CRTs and become the main US oscilloscope manufacturer. He later crashed his eponymous company by trying to break into domestic TV. Tek took the scope market and the rest is history!

rogerdup · 27th Apr 2018, 4:48 pm

At least as interesting as trying to re-construct the machine, is the history attached to it !

peter_scott · 28th Apr 2018, 3:15 pm

In the same magazine as your Globe article there is "Own Lens Disc!" on page 87. This describes lens of about 12 mm diameter with focal lengths 28 to 50 mm. You could get similar spec lenses off the shelf e.g.
https://tinyurl.com/y8k3mdgh

Although for 60 you might need to pay £270.

Peter

rogerdup · 28th Apr 2018, 7:08 pm

Thank for the link Peter.
270 L is not an investment I can afford for this project.
Regarding the 30 centimeters of the scanning disc diameter of this machine, I calculate the window picture to be 11 millimeters high by 16 millimeters wide. This really very small and need a drill tool diameter of 0.18 millimeter diameter for punching the hole as a reference for centering the lens. I have not been facing such reduced window in my previous 60 lines prototypes and I am not sure to be able to get through this as said before.
I have ordered lens of 7mm diameter with focal 11mm for test.
Anyway a good new: found a DC motor 1600rpm -37 volts, suitable for driving the scanning disc and to be synchronized by a PLL.
Roger

rogerdup · 29th Apr 2018, 7:44 am

I am thinking to put in place of each hole a 3mm led very low angle.
All connected in parallel. I think they would be similar to the light that was passing through the lens.
To be tested today finger crossed..

julie_m · 29th Apr 2018, 8:18 am

Nice bit of lateral thinking there!

I see no reason why moving the actual light source, rather than an aperture in front of a single, fixed light source, shouldn't work .....

peter_scott · 29th Apr 2018, 9:04 am

Excellent idea!

Peter

rogerdup · 29th Apr 2018, 4:41 pm

I am not sure that this solution will work but anyway the fun is in experiments.
I will tell you what happen.. keep the suspense on

I had no time to test it today, I was in the radio club sorting an testing bulb shaped valves most of them dud.

Panrock · 29th Apr 2018, 5:08 pm

Quote:

Originally Posted by rogerdup

I am thinking to put in place of each hole a 3mm led very low angle.
All connected in parallel./

Hi Roger. How are you going to connect them to power, on the moving disc?

Or maybe I have misunderstood...

Steve

Dave Moll · 29th Apr 2018, 6:56 pm

I remember a display some years ago at the NBTV Convention using a drum of LEDs. Unfortunately, I don't recall whose it was nor how they supplied power to the LEDs, though presumably it used a sliding contact to connect to whichever row of LEDs was in the display position. A similar arrangement could probably be used around the disc, lighting each LED in turn.

julie_m · 29th Apr 2018, 8:42 pm

If there is an aperture mask in front of the disc, then there will be no need to have only one LED lit at a time. The whole chain could be connected in series or parallel, and modulated alike; only the diode in the aperture will contribute to the visible image. And it's probably using less power having 59 LEDs that nobody is going to see, than the heater of the valve that is amplifying the video signal with which they are driven .....

Dave Moll · 29th Apr 2018, 8:47 pm

True, the drum display I saw didn't use an aperture mask.

rogerdup · 29th Apr 2018, 8:57 pm

I Steve and Dave,
For the leds I need only use two wires and one going from one to the other. There is two thin wires going from first led to last led fixed on the disc. At the end the two wires goes close to the shaft and one connect to a brass circular plate with a spring contact.The other wire connect to the ground. So is also the motor shaft and no other special circular contact is needed for this one.
If the 3mm led is for 3v5, That's for 60 in serie a 210 volts to feed them. Seems to be compatible with my idea to drive them with a vintage valve 47 type.
Hi Julie,
Right. I will use a windows aperture very small on a 30 centimeter scanning disc. I plan to display on a grounded ? sanded? glass.

julie_m · 29th Apr 2018, 9:09 pm

True. I was doing my own calculations in my head, and it seemed reasonable to drive a series string of LEDs directly from the anode of a valve like that. Though I was estimating 180V

If you find you have not got enough HT to light 60 LEDs in series, you could always split them into two strings of thirty (perhaps with separate series resistors to help equalise the currents and therefore the brightnesses), or a string of 30 parallel pairs.

25th Apr 2018, 6:37 pm	#1
rogerdup Retired Dormant Member Join Date: Jan 2018 Location: Chamalières, France. Posts: 167	Globe Television project (mechanical) Hello Gentlemen, Some friends ask me to go again on a mechanical TV project. I found on the ETF pages a link to the hawestv.com literature. The Globe Television Corp. Us midget set made in 1932 described there caught my attention. Only poor photos of this set are available I think. Based on the size of the tubes appearing on the back, I could imagine the average size of the machine that is :64cm high, 45cm width, 30cm depth. A big midget. The nipkow/brillouin scanning disc is 30cm diameter and made for 60 lines. So, I think to get started with it, but first need to understand how the crater lamp and the lens were acting together to project the 4x5 inches pictures. If somebody has info about this, I would be very grateful. No problem to make a similar cabinet, nor for finding the bulb lamps. Roger Attached Thumbnails

25th Apr 2018, 7:53 pm	#2
Dave Moll Dekatron Join Date: Feb 2005 Location: West Cumbria (CA13), UK Posts: 6,127	Re: Globe Television project (mechanical) You might also find this a useful site. __________________ Mending is better than Ending (cf Brave New World by Aldous Huxley)

25th Apr 2018, 8:19 pm	#3
peter_scott Dekatron Join Date: May 2003 Location: Edinburgh, UK. Posts: 3,274	Re: Globe Television project (mechanical) You can get valve list here. You weren't far off with the dimensions. http://www.americanradiohistory.com/...32-May-Jun.pdf Page 103 says that the scanning disc has 60 lenses (not just pin holes). See also the projector at the foot of page 105 and article on page 108 not mention page 87 and few others. Peter __________________ http://www.nostalgiatech.co.uk https://www.youtube.com/c/PeterScott/videos Last edited by peter_scott; 25th Apr 2018 at 8:41 pm.

25th Apr 2018, 9:11 pm	#4
peter_scott Dekatron Join Date: May 2003 Location: Edinburgh, UK. Posts: 3,274	Re: Globe Television project (mechanical) 1931 Nov/Dec Television News page 338 article on crater tubes. 1932 Television News Sept/Oct page 190 there's an article on crater lamps and the next article is on Lens Disc Design. Peter __________________ http://www.nostalgiatech.co.uk https://www.youtube.com/c/PeterScott/videos Last edited by peter_scott; 25th Apr 2018 at 9:27 pm.

25th Apr 2018, 9:46 pm	#5
rogerdup Retired Dormant Member Join Date: Jan 2018 Location: Chamalières, France. Posts: 167	Re: Globe Television project (mechanical) Thanks Dave and Peter. Reading the litterature, this lens scanning disc appear very complicated to make, and I think we wil have not sufficient skill to go through it. Fist difficulty: find 60 lens correct type for this application! Thanks for reminding me the Radiomuseum source..I got the real sizes Roger

26th Apr 2018, 7:58 pm	#6
rogerdup Retired Dormant Member Join Date: Jan 2018 Location: Chamalières, France. Posts: 167	Re: Globe Television project (mechanical) First step, on the way to build the prototype: the bulb shaped valves. From left to right: UP: Two 24 tetrode RF amplifier One 80 rectifier LOW: 27 detector, 24 1st préamplifier, 27 2nd preamplifier 47 power amplifier (the originals 45 not affordable) 47 power amplifier. The p.a. tubes connected in parallel. To be continued (I think..) Roger Attached Thumbnails

27th Apr 2018, 1:03 pm	#7
wd40addict Octode Join Date: May 2009 Location: Stevenage, Herts. UK. Posts: 1,518	Re: Globe Television project (mechanical) Interesting it seems to have been at least partially designed by Alan DuMont. Later to get into CRTs and become the main US oscilloscope manufacturer. He later crashed his eponymous company by trying to break into domestic TV. Tek took the scope market and the rest is history!

27th Apr 2018, 4:48 pm	#8
rogerdup Retired Dormant Member Join Date: Jan 2018 Location: Chamalières, France. Posts: 167	Re: Globe Television project (mechanical) At least as interesting as trying to re-construct the machine, is the history attached to it !

28th Apr 2018, 3:15 pm	#9
peter_scott Dekatron Join Date: May 2003 Location: Edinburgh, UK. Posts: 3,274	Re: Globe Television project (mechanical) In the same magazine as your Globe article there is "Own Lens Disc!" on page 87. This describes lens of about 12 mm diameter with focal lengths 28 to 50 mm. You could get similar spec lenses off the shelf e.g. https://tinyurl.com/y8k3mdgh Although for 60 you might need to pay £270. Peter __________________ http://www.nostalgiatech.co.uk https://www.youtube.com/c/PeterScott/videos

28th Apr 2018, 7:08 pm	#10
rogerdup Retired Dormant Member Join Date: Jan 2018 Location: Chamalières, France. Posts: 167	Re: Globe Television project (mechanical) Thank for the link Peter. 270 L is not an investment I can afford for this project. Regarding the 30 centimeters of the scanning disc diameter of this machine, I calculate the window picture to be 11 millimeters high by 16 millimeters wide. This really very small and need a drill tool diameter of 0.18 millimeter diameter for punching the hole as a reference for centering the lens. I have not been facing such reduced window in my previous 60 lines prototypes and I am not sure to be able to get through this as said before. I have ordered lens of 7mm diameter with focal 11mm for test. Anyway a good new: found a DC motor 1600rpm -37 volts, suitable for driving the scanning disc and to be synchronized by a PLL. Roger Attached Thumbnails

29th Apr 2018, 7:44 am	#11
rogerdup Retired Dormant Member Join Date: Jan 2018 Location: Chamalières, France. Posts: 167	Re: Globe Television project (mechanical) I am thinking to put in place of each hole a 3mm led very low angle. All connected in parallel. I think they would be similar to the light that was passing through the lens. To be tested today finger crossed..

29th Apr 2018, 8:18 am	#12
julie_m Dekatron Join Date: May 2008 Location: Derby, UK. Posts: 7,735	Re: Globe Television project (mechanical) Nice bit of lateral thinking there! I see no reason why moving the actual light source, rather than an aperture in front of a single, fixed light source, shouldn't work ..... __________________ If I have seen further than others, it is because I was standing on a pile of failed experiments.

29th Apr 2018, 9:04 am	#13
peter_scott Dekatron Join Date: May 2003 Location: Edinburgh, UK. Posts: 3,274	Re: Globe Television project (mechanical) Excellent idea! Peter __________________ http://www.nostalgiatech.co.uk https://www.youtube.com/c/PeterScott/videos

29th Apr 2018, 4:41 pm	#14
rogerdup Retired Dormant Member Join Date: Jan 2018 Location: Chamalières, France. Posts: 167	Re: Globe Television project (mechanical) I am not sure that this solution will work but anyway the fun is in experiments. I will tell you what happen.. keep the suspense on I had no time to test it today, I was in the radio club sorting an testing bulb shaped valves most of them dud. Last edited by rogerdup; 29th Apr 2018 at 4:48 pm. Reason: grammatical

29th Apr 2018, 6:56 pm	#16
Dave Moll Dekatron Join Date: Feb 2005 Location: West Cumbria (CA13), UK Posts: 6,127	Re: Globe Television project (mechanical) I remember a display some years ago at the NBTV Convention using a drum of LEDs. Unfortunately, I don't recall whose it was nor how they supplied power to the LEDs, though presumably it used a sliding contact to connect to whichever row of LEDs was in the display position. A similar arrangement could probably be used around the disc, lighting each LED in turn. __________________ Mending is better than Ending (cf Brave New World by Aldous Huxley)

29th Apr 2018, 8:42 pm	#17
julie_m Dekatron Join Date: May 2008 Location: Derby, UK. Posts: 7,735	Re: Globe Television project (mechanical) If there is an aperture mask in front of the disc, then there will be no need to have only one LED lit at a time. The whole chain could be connected in series or parallel, and modulated alike; only the diode in the aperture will contribute to the visible image. And it's probably using less power having 59 LEDs that nobody is going to see, than the heater of the valve that is amplifying the video signal with which they are driven ..... __________________ If I have seen further than others, it is because I was standing on a pile of failed experiments.

29th Apr 2018, 8:47 pm	#18
Dave Moll Dekatron Join Date: Feb 2005 Location: West Cumbria (CA13), UK Posts: 6,127	Re: Globe Television project (mechanical) True, the drum display I saw didn't use an aperture mask. __________________ Mending is better than Ending (cf Brave New World by Aldous Huxley)

29th Apr 2018, 8:57 pm	#19
rogerdup Retired Dormant Member Join Date: Jan 2018 Location: Chamalières, France. Posts: 167	Re: Globe Television project (mechanical) I Steve and Dave, For the leds I need only use two wires and one going from one to the other. There is two thin wires going from first led to last led fixed on the disc. At the end the two wires goes close to the shaft and one connect to a brass circular plate with a spring contact.The other wire connect to the ground. So is also the motor shaft and no other special circular contact is needed for this one. If the 3mm led is for 3v5, That's for 60 in serie a 210 volts to feed them. Seems to be compatible with my idea to drive them with a vintage valve 47 type. Hi Julie, Right. I will use a windows aperture very small on a 30 centimeter scanning disc. I plan to display on a grounded ? sanded? glass. Last edited by rogerdup; 29th Apr 2018 at 9:03 pm.

29th Apr 2018, 9:09 pm	#20
julie_m Dekatron Join Date: May 2008 Location: Derby, UK. Posts: 7,735	Re: Globe Television project (mechanical) True. I was doing my own calculations in my head, and it seemed reasonable to drive a series string of LEDs directly from the anode of a valve like that. Though I was estimating 180V If you find you have not got enough HT to light 60 LEDs in series, you could always split them into two strings of thirty (perhaps with separate series resistors to help equalise the currents and therefore the brightnesses), or a string of 30 parallel pairs. __________________ If I have seen further than others, it is because I was standing on a pile of failed experiments.