Assembly notes

Neons

Use 33kOhm resistors for HV507 outputs (schematic has 100k and I’m too lazy to fix that)
It took me a bit to get a handle of shaping the leads. You can look at the detailed pictures to get some inspiration. The critical thing is to keep safety distance between the leads as well as between leads and pcb traces. The original intention was to use 4x12mm neons for minutes (outer ring), 5x13 neons for hours (inner ring) and 6x16 neons for hour marks. HV507 struggled to supply enough current and as a result, 6x16 neons weren’t lighting properly. 4x10 also have some minor issues but in the end it’s fine. 5x13 have the best performance so I’d probably suggest to just use those.
One neon at the bottom (between DC jack and bottom nixie) needs special care so that there’s big enough gap between the jack and neon leads. Use multiple layers of electrical tape or other means of separating them.

NL-5870: This is the tube I used. Should be offset by about 3mm off the pcb (glass to pcb distance). I suggest to solder two pins and adjust the position as needed so that they are perfectly positioned. Don’t rush it, take your time. “9” and “3” tubes are especially important to position just right, so they are in the middle of the board.
NL-5750: This tube can be used (untested). If you were to use this tube, make sure to double check the pinout and make new daughter boards if needed. As opposed to the NL-5870, this tube has higher base so it should be seated flat on the PCB.

This board use unique SMD placement of the SN74141 drivers. You take the chip, bend the legs, lightly press the IC on the board and solder like that. I used sockets so that I can replace the ICs if needed. When using sockets, you will need to strip the leads after bending because they are too long.
While the board is designed for SN74141, there are pin-compatible alternatives like MH74141 from Tesla or soviet K155ID1. I personally recommend using old stock SN74141 / MH74141 because the soviet ones are low quality. SN7441 can be used but can’t be blanked.