Lately encouraged by Dave's Nixie display project I've managed to finish my own nixie clock which I was planing to build for a couple of years.
I've built high voltage power supply based on a famous
Pile-O-Poo project which gives me a nice and stable 180V output voltage.
For driving nixie tube cathodes I've used exactly the same IC like Dave used: TPIC6B595
8-bit shift register. Output drains are connected straight to nixie cathodes. Nixie (
IN-8) anode is connected through a 30k resistor to high voltage power supply. The shift register clock, data, enable, VCC and ground lines are connected to Arduino.
Unfortunately not all things went as I expected. I'm facing with an issue. When I set the shift register output the nixie tube number is glowing nice and bright (the current is under 1mA), but when I turn off the output the number is still partially glowing. The voltage difference between ground and drain is about 50V. It looks like there's a current leakage between source and drain (Idss). How to prevent it? I've tried to rise the resistance on nixie anode, but it results now with partially glowing cathode when the output is set.
I'm surprised that Dave didn't have such a problem with his nixie display because I did everything the same like he did. Only the tube I used is different (IN-8). But they seems to have similar parameters.
Can someone give me a clue what do I suppose to do to fix this issue?