Just took a quick look at my stash, and I also have a bunch of IN-1s coded 9205. I'm not sure if it's worth it to design something around them, then — if they fail so quickly and easily.
--J. > On 17 May 2015, at 07:27, gregebert <[email protected]> wrote: > > My driver circuit is a direct-drive constant-current source, and it was set > to the IN-1 spec current of 3.0mA. I was only using one numeral in each tube, > so all undriven cathodes were floating. The clock uses 15 tubes to display 1 > thru 12 on the clock face (it's a large neon-equivalent of a regular > mechanical clock) so the numeral is displayed constantly. > > What I found is that after a few days there would be 2 glowing cathodes: The > desired numeral, and the adjacent cathode closest to the front of the tube. I > confirmed a low-resistance short of a few ohms was present. I kept a lot of > notes, but I would need to dig around for them. I also found that the short > was caused by a tiny filament that formed between the cathodes by passing > about 100mA which caused it to glow. It usually took 300 to 500mA to zap the > short; it acted like a fuse. Afterwards the tube functioned as expected. > > As I ran my clock longer, I noticed more tubes failing in the same manner, > and each time I was able to zap them back to life. It got ridiculous having > to zap another tube almost every day, so I replaced them with Burroughs tubes > and never had any trouble. > > I suspect the filament was growing in the direction of the electric field > between the cathode and anode, and grew until it shorted the adjacent > cathode. I dont have the equipment to analyze the chemical makeup of the > cathodes or the filament that formed. I do know it was very small diameter; > not visible until it was made to glow. > > NASA has done considerable research on tin whiskers, which is probably a > similar mechanism to what was failing in my IN-1 tubes. They form in electric > fields. > > I've heard that IN-1 tubes do not contain mercury, whereas Burroughs (and > many other brands) do contain mercury. Perhaps there is some odd role mercury > plays in preventing the formation of these filaments. > > I suspect that after the USSR broke into separate nations that different > materials or processes were used in IN-1 manufacturing; there may have been > relaxed quality standards as well. My tubes are all date-coded 9205. > > I have an A101 dekatron spinning 24/7 on the same clock, and it's been > running flawlessly for more than 2 years. Despite a much higher operating > voltage (hence higher electric field), it's fine. > > -- > 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 [email protected]. > To post to this group, send email to [email protected]. > To view this discussion on the web, visit > https://groups.google.com/d/msgid/neonixie-l/53216fa6-0cd4-4b97-a0e1-7b0daccf73e6%40googlegroups.com. > For more options, visit https://groups.google.com/d/optout. -- 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 [email protected]. To post to this group, send an email to [email protected]. To view this discussion on the web, visit https://groups.google.com/d/msgid/neonixie-l/C899E94F-B0FA-40A9-BD62-95C04A8593F1%40gmail.com. For more options, visit https://groups.google.com/d/optout.
