Globe Television project (mechanical)

[Refugee]

I would beware of the fact that when a motor is running at speed the bearings effectively float in their oil.
VCR's have to have a brush on the motor shaft to get rid of static and car alternators always have to have two brushes.
Neither rely on continuity through the bearings.

[rogerdup]

Right Julie. I ordered 60 x 3v/3mm/20ma leds.
180v dc is no problem given I will use a vintage 47 anode to drive them.
The mean of coupling the leds serie to the 47 anode will be the very way as the neon lamp was: an inductance in serie between the anode and the HV +. One side of the leds serie to the anode. The other connected to the ground through a pot. to control the current (brightness) and a 4 or 5mfd capacitor in patallel on the pot.

For refugee: thank for your comment. I have some experience in driving scanning disc at 1500rpm speed. Up to now, no encountered special problem. This time, I will use and old 30cm vinyl as scanning disc. So I don't know if such static problem will appear.

[Refugee]

I would be tempted to fit a reverse parallel diode across the LED chain too as there is inductance present.

[rogerdup]

Interesting. You mean connecting this led cathode to the - (ground) and anode to the +ht ? should be a 1N4007 type, right?

[julie_m]

No; this diode should have its cathode towards the HT and its anode towards the valve anode, so it is pointing in the opposite direction to the LEDs. Its purpose is to protect the LEDs from any high-voltage kickback from the inductance.

I'd personally use a 1N4007UF, which is the ultra-fast recovery version of the 1N4007.

With surface mount LEDs the whole disk could be one bit of PCB, even RGB with the right LEDs.

[rogerdup]

OK Thanks. In fact the 1N4007uf is in parallel with the inductance.

I would have to calculate the most appropriate Z value for it. Typical z for the 47 is 7000 ohms but when connected to an audio transformer, which is not the case here.

[rogerdup]

Here the scanning disc DC motor on test. It is oversized power wise, so no doubt it will drive the 30cm vinyl easily.

[julie_m]

Do you even need the inductance in series with the LEDs? Unless it serves some important performance that I am not recognising, I would think it would be better just to use a simple resistor in series with the LEDs.

You will need to measure the LED current needed for full brightness, to help with working out the valve biasing.

[rogerdup]

Right. I review some vintage schematics and they connected the neon lamp directly to the power lamp anode.
I was trying the effect of the 3mm led on the ground glass. The spot appear too big unless the glass is very close to it. So I ordered the 1.8mm to try .

[rogerdup]

Here a schematic I made for putting leds and hole on the scanning disc. Not tested yet but should work. Using 3mm leds ultra bright recommended.
Roger
Note: this for the Globe 60 lines machine. Windows 12mm by 16mm.

[Dave Moll]

I assume the rather unfortunate word in the line about the next hole should read "shift".

[rogerdup]

Wow, yeah too bad.. I have to improve my grammatical

[rogerdup]

Originally Posted by rogerdup

Here a schematic I made for putting leds and hole on the scanning disc. Not tested yet but should work. Using 3mm leds ultra bright recommended.
Roger
Note: this for the Globe 60 lines machine. Windows 12mm by 16mm.

Updated drawing.

[rogerdup]

Hello friends interested in mechanical television and others..
The following photos to show the progresses in bringing the project to life.
I found a suitable chassis to build the Globe machine receiver on it. I will put
3 RF stages with 57 type tubes as I had no place for 24 types shield. The receiving band will be between 100 and 150 meters. In a following message, I'll explain the coils construction, and how it match with the 3 cages CV.
The globe lamps in front are from left to right 27 detector, 24 preamp. audio and 47 power amp. socket in the middle of the 47 and 24 is for connecting leds and/or motor power. At the back is a globe 80 rectifier(heater open, I have to find another one )
The third photo show the electronics for the 12v modules power supply, and the adjustable regulated voltage for motor speed control. On the two green plates are the PLL (G4JNU) for motor driving and synchronous signal coming from the opto fork.
Also, I made circuits to drive a led to make easy the viewing on the stroboscope disc to control the speed at exactly 1500 rpm.
Roger.
Note: I will definitively discard the use of a vinyl as a scanning disc, but I assumed this was understood based on my last messages

[rogerdup]

Hi Everybody,
Updating my last message about the medium wave receiver for the 60 lines Globe Machine replica project.
The receiver is completely terminated with some modifications since the first study. The two first stages uses 58 and all uses a grid tuned circuit instead of the tuned anode, thus avoiding having the CV cages put at the HT potential as in the original Denton 1932 TV receiver.
By carefully choosing the screen and anode resistors value, the sensibility appear to be correct for such a type of anode curve detection.
I'll be back with the scanning disc manufacturing progress.
Roger

[rogerdup]

Scanning disc on the way for delivery end june. Diameter will be up to 362mm and use of 1,8mm 4000mcd leds. Early tests with the final power tube 47 has been successful. The windows picture will be 20mm width by 18mm height. The 47 plate is loaded by a 1120 ohms resistor. I put the final schematic if people are interested .
To be continued by the cabinet manufacturing..
Roger

[dalekmoore2007]

Hi sounds a bit like my Inductionvisor experiments about a year ago video in the link page i had only manual sync control as i was mainly just interested in if the modulation powering idea would work.
http://www.taswegian.com/NBTV/forum/...php?f=1&t=2303
Even ended up using leds behind the disk
I wanted to power and video modulate the leds at the same time all via inductance or radio what ever you want to call it ...sure worked
No mechanical wear or noise using this system
So rotating the leds is worth using ...you can have each led have its own receiver or as i did lazy way one for all of them ..if you have one for each Led you would have a induction mask no need to make one then.

[rogerdup]

News about the Globe machine replica. Things are in progress. The mecanician agree on building the scanning disc with 1,8mm leds and a hole of 0,24mm in front of them. I had to increase the disc diameter to 360mm to get a picture not too small given I don't know how much I will be able to expand the image. The overall size of the machine should not differ that much from the original. The disc will rotate at 5mm from the inside cabinet.
In any case, for interest or comments, I put the schematic of the receiver here after. The structure is very similar to what the machine had but the 45 triodes replaced by a 47 and the 24 RF by 58. There is no DC restorer here, but I didn't saw any either, in vintage receiver this period.
Roger