Wang 300 Calc

Brent Hilpert hilpert at
Wed Sep 5 17:10:41 CDT 2007

Jason T wrote:
> > I've got a line on one of these old Nixie-tube calculators at
> > a fair price.  I know they used an outboard processor, making
> > them little more than (very pretty) terminals to a central
> > CPU.  Are they of any use other than a doorstop or eye candy
> > for the collection?  (And don't say "harvest them for the Nixies!")

Rick Bensene wrote:
> The 300 - Series Wang Calculators consisted of two parts: an electronics
> package, and
> "Keyboard/Display Units".  The electronics packages are usually
> small-briefcase-sized (single-user) or longer, shorter packages with a
> connector (or connectors for the multi-user versions)  that the
> keyboard/display units plug into.
> The Keyboard/Display units are pretty much useless by themselves -- they
> need the "brains" in the electronics package to do anything.  All the
> keyboard/display units consist of are a keyboard and keyboard encoding
> circuitry, and a Nixie tube display with display decode/driver
> electronics.  There are no mathematical electronics in the
> Keyboard/display units.
> The keyboard/display units have pretty simple circuitry inside them.  It
> wouldn't be too hard to build some kind of microprocessor or
> microcontroller-based gizmo that would emulate the electronics package
> and bring a Keyboard/Display unit to life.  You'd need some good math
> knowledge to implement the various math routines, but the interface is a
> very simple multiplexed BCD display, and a six-bit key code for each
> key, encoded by a diode matrix.

I received two orphan 320K keyboard/display units a few years ago (no logic unit).
Hobbled up a little level-shifting hardware and wrote some calculator code to
drive them from a SWTPC 6800 - in other words the 6800 was replacing the
missing logic unit. Worked fine but the next (intended) step was to redo it
all in a microcontroller and stuff it inside the 320K case so it would be a
stand-alone 'modern' nixie desktop calculator. Would be kinda nice because the
320K KDUs have a small footprint compared to other nixie desktop calcs. There
is very little spare room in the case however. I think I anticipated it would be
feasible if one used an external wal-wart (ugly) for the power transformer.
The KDUs are very well built: cast aluminum case, micro-switches for the keys...

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