If you have an oscilloscope, debug will be easier. Have you tried biasing the anodes to a lower-voltage during the off state ? If they are at a voltage lower then the sustaining-voltage, the digits will stay dark. Typically this is done with a large-ish resistor tied to 1/2 the HV supply voltage. If that's not convenient, you can use a pulldown resistor. I would experiment with 1Meg-to-gnd and see if that does the trick. If the glow is less, then try a slightly lower value. You want to use as high a resistance as possible to minimize wasted energy.
As far as the cause, my first guess is the anode transistor is a tad leaky. I didn't look-up the datasheet info, but if Vceo (bipolar) of Vdsmax (NMOS/PMOS) is less than the anode supply voltage, you're entering a gray-area (yes, I'm aware that people use lower-rated Vceo devices because of the voltage-drop across the tube. I never do, but it's my money so I spend a bit more for over-designed devices). Next, check the leakage currents (Icbo, Iebo). Bipolar devices should be well under 1uA. I typically choose devices at 100nA or less because of transistor 'beta'. For NMOS/PMOS, I try to get Idss around 1uA, but my first clock was 25uA and it works fine. Forget about tube capacitance; I measured less than 10pF on my 5092''s Someone already mentioned direct-drive, and all my designs use direct-drive (even my wristwatch). Not sure if that's an option for you at this point. -- You received this message because you are subscribed to the Google Groups "neonixie-l" group. To unsubscribe from this group and stop receiving emails from it, send an email to neonixie-l+unsubscr...@googlegroups.com. To post to this group, send an email to neonixie-l@googlegroups.com. To view this discussion on the web, visit https://groups.google.com/d/msgid/neonixie-l/10fdcddd-1510-4d11-92c2-edfdec6843a2%40googlegroups.com. For more options, visit https://groups.google.com/d/optout.
