Nixie tubes come in many sizes and display styles. The most common tubes are numeric, meaning that they only display a single digit from zero (0) to nine (9). Each digit is an individual cathode, and they all share a common anode which is typically the mesh visible on the front of the tube.
Above Image: National 840 nixies, you can clearly see the anode mesh in front of the digits, stacked front to back. This is by far the most common type of nixie construction, although many variants do exist.
As beautiful as numeric nixies are with their ‘organic’ curvy digits, there is a limit to the amount of useful information they can display. That is why I opted to build a full fledged alphanumeric clock, which boasts some of the largest tubes you can still find today.
This clock design is the MOD-SIX; a six (6) tube clock designed by my friend and talented electrical engineer Mr. Henry Carl Ott. The tubes it uses are 4 inch tall Burroughs B7971; which are massive 15 segment alphanumeric nixies!
The MOD-SIX is sold on-and-off as a complete clock without tubes at badnixie.com (be sure to check this site out; lots of other cool nixie clocks!). Keep an out for the next batch if you’d like your own.
The clock I assembled here is a little special, as I was able to get the bare PCBs and populate all the components myself. I also made the acrylic case. You can check out this very MOD-SIX being soldered together and powered up on Youtube:
But wait! There’s more…
Of course, one clock is not enough for nixie fanatics such as myself, so I had to pick up a special edition clock also made by Ott and Barile; the “Black Emerald”, which is a ‘baby’ version of the MOD-SIX:
The Black Emerald uses the same CPU design as the MOD-SIX. It also uses Burroughs 15 segment alphanumeric nixies: specifically, the Burroughs 8971 tube. These medium sized tubes are actually much rarer than their big brother! The Black Emerald was offered as a complete kit only, with a very nice anodized aluminum art deco enclosure. It pairs well with its larger counterpart. You can see both the 8971 and 7971 tubes being offered in this Burroughs Brochure from 1970:
Stay tuned for more rare and unusual nixie projects!