I did nothing heroic. I used the cheapest transistors I could find (PolyPaks, John Meshna, etc.) and carbon comp resistors. I used the resistor values in the old "73 Magazine" article "Build a Giant Nixie Clock" from the mid-1970s, and increased the HV power supply voltage until it was "bright enough" (about 175V on my old Lafayette VOM). The resistor values may have changed with time, but I think they were initially 1-2ma per segment.
I built three clocks with a total of 18 tubes. So far, after 40+ years, there have been zero tube failures. The $20 I spent on spare tubes (at $1 each) has been a waste of money. The tubes were multiplexed. I found that the biggest problem is that the tubes sing at the mux rate, and the volume increased with the drive current. (Someone once suggested that the sound was coming from the power supply, but this was way back in the old days and I only built linear power supplies operating at the line frequency of 60 cps.) On Friday, August 19, 2016 at 9:00:55 AM UTC-7, gregebert wrote: > > According to the b7971 datasheet, the maximum allowable current is 21mA. > Yet when you add-up the currents for each cathode to produce the '8' or > '*' characters, they add up to 40mA, which is way over the spec limit. > > For those of you who design their clocks, did you scale-back all segment > currents so they never exceed 21mA ? > > I'll probably current-limit each cathode individually, and put another > current-limit on the anode. Even though that adds up to a lot of > transistors for a direct-drive clock, these tubes are getting pretty scarce > and expensive so I'm not taking any chances. > > > > -- 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/3acb2b95-6cd8-48a2-9d14-586f95b413d0%40googlegroups.com. For more options, visit https://groups.google.com/d/optout.
