Electronic – Nixie tube equivalent circuit model and transients

Sure, it would work.

I have used a slight step-up transformer (120v to 130v) to drive a nixie supply. It also had a 6.3v filament tap which was really convenient for the 5v ttl logic supply. However, I used a full-bridge rectifier followed by a electrolytic capacitor to filter both supplies. Here's why I would recommend that setup over what you're suggesting:

• It's cheap. For $1.25, you can have decent regulation of your supply voltage. I'm assuming the isolation transformer is already accounted for.
• You can/will see the nixie tubes flicker at 60 Hz.

The motivation for fancier regulation circuits is to protect the nixie tubes. They are usually the focal point of any design using them, so it's in the designer's best interest to make sure nothing bad happens to the tubes. I've seen people drive nixie tubes with expensive regulated bench supplies, and read about people using unisolated circuits. Somewhere in that range is a cost-benefit-paranoia tradeoff.

Yes, all the components need to share a common ground (if you're paranoid you can have the high voltage ground connect to the low voltage ground in one place through a ferrite bead). The "outputs" you're talking about for the BCD are just acting as switches to ground, so they don't experience the high voltage and small current on the same time. When turned on (switched to ground), most of the voltage is dropped on the Nixie tube segment and series resistor. When switch off however, they'll see the full voltage. It's difficult to tell from the linked data sheet what voltage they can handle, the part that's in English talks about a DM54/DM7441A, while the Russian part looks like it's about the K155ID1s. The two parts of that datasheet can also be found independently online, so I'm not sure if they're supposed to be pasted together. It certainly looks like people have been using these with 170VDC, so they very likely work, though the lifetime may be degraded. I'd say go for it, the chips are only $0.90 some places.