Hi John,
The scans you posted answer all of the questions.
There is no "display controller" as you'd expect from the modern "fruit 
machine" displays.
All we have on the board is latches and level shifters.
pins 16,18,19 control a shift register (TL5812) to select the digit 
position to display (both displays selected at the same time)
there are then 4 latches - 2 for segments on top display, 2 for segments on 
bottom display
These latch the 8 bit data bus (pins 4 to 11) to each level shifter.
the first 3 latches are internal to an 8255 (antique i/o port that I last 
used in the early 80s) - selected with /A7 (pin3) low , /SEL4 (pin 13) low 
and /WR (pin1) low /RD (pin 2) HIGH
A0 and A1 (pins 14 + 15) select which one of the 3 latches to use (and 
initialise the 8255)
As this part only has 3 latches and we need 4, an extra latch has been 
bolted on in the form of IC2 (74ls273)
This is selected with /SEL4 (pin 13) low, /A7 (pin 3) HIGH, /WR (pin1) low
(I think reset should be kept high - need to check data sheets)
Supplies are 47v, 5v, 4.5vAC for the filament.

Data sheets are available for all of these chips.
I suspect that driving one is "a full time job" for something like a simple 
arduino.

I hope my ramblings help someone,
Cheers,
Andrew


On Tuesday, June 4, 2019 at 9:52:24 AM UTC+1, Nixcited delighted wrote:
>
> I now have my displays and the schematic.
>
> I have scanned relevant manual pages, power supply, interconnect, display 
> board and component identification.
>
> https://www.dropbox.com/s/bltgd4w4o9gonuy/Alvin_G_Display.zip?dl=0
>
> John S
>

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