The sticking on K10 specifically is a peculiarity of the 6167 in my experience. I believe it's distinct from the sleeping sickness effect that Martin describes as that is essentially random in which cathodes are affected (and as he says, working the tube, possibly at elevated current, in both directions where possible, is usually an effective cure).
I mostly saw K10 sticking when I was exploring a circuit that makes use of the unique auxiliary anode connection (pin 5) which of course lies adjacent to K10. What seems to be happening was that when the glow gets to K10 there is current flow from both the main anode and auxiliary anode. The next transfer pulse moves the glow onto the transfer electrode, but when it terminates the auxiliary anode-K10 gap is still sufficiently primed so that the glow mostly steps back to K10 rather than forward to K1. I was able to mitigate this by reducing the auxiliary anode potential below what I'd originally understood it needed to be from the datasheet (the datasheet is really opaque on this point), and also by lengthening the transfer pulse to allow more deionisation time. However, if I understand Paolo's post, he's using Mike Moorrees's circuit ( https://threeneurons.files.wordpress.com/2011/09/we6167ckt.gif) which leaves the auxiliary anode disconnected. When I ran 6167s in this configuration they were generally much more reliable in not sticking on K10, though I was using rather different circuit conditions: - Va = +400V with respect to main cathodes - Transfer pulses 60V amplitude from a resting bias +30V with respect to main cathodes - Anode current 1.3mA Paolo, can you confirm you have indeed left pin 5 unconnected? If so, given that the sticking effect seems to be increasing with tube use, I wonder if we're seeing the floating auxiliary anode gradually charging up and eventually reaching a potential which is disrupting the stepping operation. Maybe use a potentiometer or potential divider to pin the auxiliary anode at some moderate voltage positive to the main cathodes (say +100V as a starting point) and see if that helps? They're funky tubes... Jon. On Wednesday, February 23, 2022 at 8:37:58 AM UTC Paolo Cravero wrote: > Hello. > I am stuck with a stubborn WE-6167 dekatron ( > http://www.tube-tester.com/sites/nixie/dat_arch/6167.pdf seems to be the > only document available). > > The tube is NIB made in 1958. I understand it is a single guide dekatron, > and the stepping cathodes are split in two groups 1-5 and 6-10. > > I built the circuit as per Mike's diagram ( > http://www.tube-tester.com/sites/nixie/dat_arch/6167.pdf) and it span > correctly. I let it run for few minutes and then it got stuck at K10. > Through the glass I can see that it attempts to jump ahead, but the main > glow stays on K10. Fiddling with wires I could get it have one round up to > K10. The more it runs the more it gets stickier. The relaxation oscillator > never stops. > > I suspected some resistor overheating or changing value, but even after > hours of power-off, it doesn't go beyond K10. Or it simply powers up at K10 > and doesn't step over, while it does visually try to jump. > > Voltages are 450V/225V (input at 12V is 220 mA). Anode current is 1 mA (I > increased the anode resistor to 250k) while the current coming out of the > active cathode(s) is 1.5 mA. Stepping goes from 200V down to 2V (green > trace). Anode voltage (450 V) doesn't sag noticeably and inductor+IRF get > barely warm. The yellow trace in the oscilloscope shot is measured at the > "+58V" point (yes, I did try to move that voltage up and down with no > difference). > > > Then I opened a second new in box WE-6167. It ran correctly for a minute, > perhaps 100 rounds, then it started hiccupping (I think between K5 and K6) > and finally got stuck on K10 with the flicker towards the stepping cathode. > > It must be something with these tubes. Does anyone remember a similar > behaviour in never used dekatrons? I've read of deks needing a high current > "preparation", but not of them failing after a good start. I would like to > get out of the K10 position! > > Thanks, > Paolo > > -- 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 view this discussion on the web, visit https://groups.google.com/d/msgid/neonixie-l/a5921b69-9cb2-49c2-b543-283ab0a889d9n%40googlegroups.com.
