This is a bit of a retrospective on things I’ve learned since I built my first nixie clock back in 2007. Its been suffering from what looked like cathode poisoning for a while, so I discontinued its use and decided to upgrade it.
First let’s look at the specs. It’s built using point-to-point wiring on two stacked boards. The top board consists of 6 Russian IN-14 nixie tubes. These are driven by 6 Russian KM155ID1 equivalents to the 74141 nixie decoder/driver, driven in turn by 3 74HC595 latching shift registers. The top board also includes six LEDs that provide blue uplighting of the nixie tubes.
The lower board contains a 5V linear regulator (a 7805), a high voltage power supply built around an NE555, a Picaxe 18X MCU, a DS1307 real time clock, some switches and a MOSFET to drive the LEDs with a PWM signal.