My 70's nixie clock


As the reader can see across my pages, I always got a certain attraction for digital clocks. This one got designed and homemade in 1971-72, at a time where integrated circuits were very new and led displays were not known to be existing.

This is just to add at the fantastic collection of nixie clocks on the web.



Today, time of writing, the design is what we call a classic design. An oscillator crystal driven is divided with a programmable divisor to obtain a 1 second frequency.

The 1 second signal drives 6 decades counters to count seconds, minutes, hours. For each decade, the counter outputs drive a high voltage BCD decoder 74141AN directly connected to the ZM1000 nixie tube ( See ref1 for datasheet). As nixies behave like neon tube they need about 250 Volts supply voltage to fire up, and a serial resistance to limit current after fire up.

Time is setup manually on hours and minutes with a switch and a push button.

picture of clock front panel

The pins and wires, on front panel, are to setup the time to start and to stop the power on the connected channel. This channel drives a 220V plug where you can connect some appliance.

picture of clock internals

The power supply is on the left. The vertical boards, on the right, support the divisors and are soldered on the main board, so are the BCD decoders and nixies.


The clock can still work, but needs a battery to preserve time during power losses, that are sometimes very frequent.


Scanned copy of the original schematics can be found in the download section.


  1. Ref1: nixie ZM1000 datasheet