These are front and back pictures of a Burrough's B-7971 Nixie Tube clock that I built back in 1979 when I was a senior in High School (I designed the PC board on October 1, 1979). The digits are 2½ inches high. The clock circuit is based on a schematic that had been provided by the surplus parts vendor along with the three stock exchange ticker display cards that the tubes and sockets came from. The ticker card also had some high voltage switching transistors that were used in the construction of the clock. The clock uses a National Semiconductor MM5311 clock chip and uses the 60Hz line frequency as its time base. Unfortunately, the original circuit was a very poor transformerless design and blew several capacitors, resistors and Zener diodes during its initial test run (it was spectacular!). I wound up making my own design changes, including adding a transformer, and it has worked fine ever since it officially went "live" on February 11, 1980. Over the years, I have replaced some parts with newer smaller components but it still uses the original clock chip and high voltage transistors that came from the stock exchange display card. Back in 1979, I was a cash strapped student and did not have the money to purchase the best parts except for a rather hard to find 160V/10W Zener diode that I obtained surplus. I designed the PC board and wooden stand myself. I currently have seven brand new spare B-7971 tubes that I purchased 15 years ago. However, after almost 20 years of continuous operation (the clock took a break when I was away at college), the original tubes are still working fine and show no signs of needing replacement.

To learn more about Nixie tube clocks, visit Mike Harrison's Nixie Tube Clock Page at http://www.netcomuk.co.uk/~wwl/nixclock.html. Be sure to visit the Nixie Clock Gallery at http://www.netcomuk.co.uk/~wwl/nixiegallery.html where this clock is also listed.

The IEEE published an article on Nixie Tubes in their June 2002 issue of Spectrum. The article is available to members (login required) at http://www.spectrum.ieee.org/spectrum/jun02/features/nixi.html. It is also available to anyone at http://www.amug.org/~jthomas/ieeenix.html.