> I have a display in mind that would fire off random cathodes, some at the at the same time. However, I'm not sure if this: a) would work ok, and b) be ok for the tube (cathode poisoning?)
Aside from multiplexing, the way to do this reliably is to use individual cathode resistors instead of a shared anode resistor. As long as you keep the total current reasonable, I don't think it would harm the tube at all. Cathode poisoning comes from not using cathodes for a long time while others are lit.
- John