seven segment display history

[Brent Hilpert]

Ethan Dicks wrote:
> 
> On Sat, Mar 01, 2008 at 08:54:10PM -0800, Brent Hilpert wrote:
> > Ethan Dicks wrote:
> > > > > There is a vendor and part number etched on the face: Sperry SP-738.
> >
> > Forgot before, Heathkit used those Sperry/Beckman displays in their 70's-era
> > digital doodads like clocks, indoor-outdoor thermometers, weather monitors,
> > tachs, & c., might be a place to look for schematics for examples of real-world use.
> 
> Oh, yeah.  I even have one of those 6-digit Heathkit clocks.  Still, the
> trick with those is that some of the Sperry/Beckman displays have keep-
> alive-anodes, and some do not.  From the one link that was recently
> posted, it's clear that there was a large variety of displays made back
> in the day, and you could select a display for your requirements (especially
> how many primary anodes for multiplexing).
> 
> In this case, I have a particular display, one of the more complex ones,
> looking for an application; not the other way around.

No, I didn't mean to suggest that you would want to re-implement one of the
Heathkit designs/apps, just that the Heath schematics might be available and
might provide some circuit examples/hints of biasing techniques, drivers, & c.
(not always included on spec sheets).

e.g.: As it turns out, I have the schematic for the GC-1092 clock here (don't
have the clock, just the schematic, which has been hanging around in my files
since the 70's). It uses SP-352 displays, and shows the keep-alive cathode and
supply, etc.

Don't know why that web page refers to the Sperry/Beckman displays as Panaplex,
my understanding was Panaplex was a Burroughs trade name for their 7-seg
gas-discharge displays.