This log is just the basic background of why of the clock project - for example, why am I multiplexing, or why did I do X? Feel free to skip this log if you just want the technical details.
I have wanted to build a Nixie clock for at least 10 years now, and finally got around to it. The board that holds the tubes is scavenged from a kit from tubehobby.com (the NCV2.1-14), which was a present to my wife from her father. Unfortunately the kit sat for a couple of years before we put it together - and then it didn't work. Lacking the knowledge or experience to troubleshoot, we put it in back a box and it sat there for several moves.
This last March (2021 for those reading years in the future) I finally got it out of it's box and began troubleshooting, and discovered the control board was bad. Several connections on the board weren't making contact across their respective traces - I don't know if this is because the board was bad to begin with or because I damaged it in the hack job I did soldering. (I've since gotten better at that!) Since it was so long since it was purchased, I figured any warranty would be moot, plus I might have been the one to destroy it.
So I decided this was the perfect time to learn some basic electronics, copy the relevant parts of the circuit, and design my own board. Also I figured I could write the software since I actually already knew how to do that.
The clock kit comes with two boards, one for just the tubes, and one for all the control logic. I tested all the traces and the board that holds the tubes was fine, so I decided to reuse it. Unfortunately this meant I would have to multiplex my design - the cathodes (each digit of a nixie tube is a cathode) of the tens places are all connected, and the same for the ones place.
You control each tube by turning on it's anode. In the original design this was done with transistors configured as a high side switch. I've seen many other people do this same technique as well, so I copied that. The original designer put his schematics on line, so I was able to copy the transistor hss since that was essentially black magic to me when I started this.
Power conversion isn't really my thing though, so I decided I'd just buy the High Voltage Nixie power supply kit from ThreeNeurons and use that board directly. Also, I highly recommend reading his page if you want to learn how to make a nixie clock because he has a lot of good information. Especially if you plan on multiplexing!
This was also an excuse to design and build my own PCB. It's something I've wanted to do for a while, so this is a win. Plus, I plan on building a second clock (I have lots of tubes from years ago not part of any kit), so this project is really just a warm up act!