
Restoring an unusual vintage clock display - mmastrac
https://tinkerings.org/2016/05/21/restoring-an-unusual-vintage-clock-display/
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userbinator
These are known as "projection displays":

[http://www.decadecounter.com/vta/tubepage.php?item=10](http://www.decadecounter.com/vta/tubepage.php?item=10)

[http://www.decadecounter.com/vta/articleview.php?item=989](http://www.decadecounter.com/vta/articleview.php?item=989)

One company that makes them is still around:

[http://www.ieeinc.com/about-us](http://www.ieeinc.com/about-us)

A lot of other interesting old display technologies here:

[http://www.electricstuff.co.uk/count.html](http://www.electricstuff.co.uk/count.html)

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slig
Thanks for the links. I was curious to know how each digit is projected on the
same place. Looks like the masks are on a curved plate.

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Animats
Oh, those things. I used to use UNIVAC 1108 computers, which had the system
clock on the console with those displays.[1] It took about a hundred small
printed circuit cards to drive the thing. It actually was the system's time of
day clock, read by the computer, not a remote display of a counter elsewhere.
If the muffin fans under the console were not regularly cleaned, the clock
would make intermittent errors, which caused the operating system to have
problems. I once had to write software to detect this.

[1]
[http://www.silogic.com/Athena/Univac%201108.html](http://www.silogic.com/Athena/Univac%201108.html)

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jonah
Here's a guy who used a two digit "one-plane display" like this as a "period
correct" digital speedometer in his 1973 beetle.

[http://thegarage.jalopnik.com/project-make-the-weirdest-
peri...](http://thegarage.jalopnik.com/project-make-the-weirdest-period-
correct-digital-dash-1728464825)

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Someone
_" Which, for a clock showing HH:MM:SS, means 72 light bulbs to replace."_

??? There are only ten digits, and you don't even need all of them everywhere.
By my reckoning, you would need 3+10+6+10+6+10=45.

If you add the ability to display dd-mm-yy, you till would only need
3+10+6+10+10+10=49. I wonder what they did with the remainder. Spelling out
the word "ALARM!"?

Or did they simply ship spare bulbs inside the product?

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jsnell
I would imagine they wanted 6 identical modules just for the manufacturing
efficiency.

That still leaves the question of why 12 lights instead of 10. I would bet
that the separator colons are actually produced by a separate mask+lamp,
rather than having different masks for each digit on those two modules. I.e.
to show "8:" you light up both the "8" lamp and the ":" lamp at the same time.
That gets us up to 11. No theory on the 12th one though.

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S_A_P
One for each . In the colon?

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HCIdivision17
Almost certainly this. In one of the links by another commenter here, you can
see a voltmeter where the guy changes the decimal. The dots are bizarrely high
to be a decimal point, but right where you'd expect it if it's the bottom dot
on the colon.

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Symbiote
I didn't find that video, but several of these seem to be British made. The
decimal point in British use was traditionally centred: 3·141.

(I still write it like that, in handwriting.)

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xvf33
I had figured that it would be about NIXIE tubes but was happy to learn about
something I hadn't come across before. Pretty neat.

Here's an interesting channel on youtube I came across and the newest video
happens to be about the NIXIE tube.
[https://www.youtube.com/watch?v=jytF5bvPGcU](https://www.youtube.com/watch?v=jytF5bvPGcU)

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ams6110
When I was a kid, my dad would sometimes bring home scrap electronic equipment
from his lab and I'd have fun taking it apart. I remember one of those
displays, with the arrays of tiny bulbs.

