Neon lamps will light from a very small current, I suspect you have a leakage issue. Try connecting a 100k or so from q9's base to ground to make sure the tranny is off. Maybe reduce the 33k feeding q9's base to 10k as well so the logic low from the micro helps to hold it off. You also have the neons connected directly to the micro, you might want to isolate the micro from the neons and use a similar anode switching method as you have used with the nixies, one of the protection diodes of the pic could be conducting causing the neon to light.
On 7 Sep, 15:39, Ron Schuster <schuster....@gmail.com> wrote: > I've built a 4-digit IN-17 nixie clock based on a 1x4 mux design. It uses 4 > neon lamps, 2 for the colon, 1 for the PM indicator and 1 for the Alarm On > indicator. I have a small problem where I see a dim flicker in the lamps > that are supposed to be off. They are driven as part of the nixie > multiplexing circuit. One side of each lamp is tied to one of the digit > anode drivers. The other sides are tied together and pulled to ground > through one common MPSA42 "cathode" driver. I think I have sufficient > blanking time between the digits. Each digit is on for 1 ms and the > blanking time between digits is 100 uSec. The nixies are showing no > ghosting at all. Any help in figuring out why my lamps are not turning > fully off would be greatly appreciated. Schematics are attached. > > Schematics.zip > 93KViewDownload -- You received this message because you are subscribed to the Google Groups "neonixie-l" group. To post to this group, send an email to neonixie-l@googlegroups.com. To unsubscribe from this group, send email to neonixie-l+unsubscr...@googlegroups.com. For more options, visit https://groups.google.com/groups/opt_out.
