Surely you've effectively got 10 of those resistors in parallel so the tube current is 10x rated....
Poor old anode.... David On Wed, 31 Mar 2021, 23:02 Jon, <[email protected]> wrote: > You're putting AC across the tube? In addition to what Paul said, think > about the scenario in the negative half-cycles. There you've got ten > 'anodes' (the display digits, normally cathodes) each with their own > resistor pouring current through one 'cathode' (the normal anode box/grid), > which is definitely not sized for that current flow nor designed to have > the glow on it bombarding its surface with lots of energetic particles. So > all bets are off on tube behaviour in my view. > > In either polarity of the cycle, the common electrode might be seeing > 22.5mA through it if your initial calculation holds. But very likely it > doesn't, because that calculation assumes the normal tube maintaining > voltage which I would have no confidence in being the case under these > conditions. If the maintaining voltage drops significantly when the tube is > run like this, then your current flow will be even more than you calculate. > Maybe that's how you get to 9W. > > Ouch. Wouldn't bother putting that tube in a clock! > > Jon. > > > On Wednesday, March 31, 2021 at 10:34:06 PM UTC+1 Paul Andrews wrote: > >> You should calculate the anode resistor you need for one segment. Use >> that, then connect all the cathodes to ground. I have done this many times >> accidentally. Now the hand waving part: Imagine the connection between the >> anode and cathode is a resistor and you connect all of the cathodes >> together - you are putting all of those resistors in parallel. You are >> limiting the current on each one to 2.25mA, so you are pumping 22.5mA >> through the one tube. I get that to be about 2W - (230-140)*0.0225. >> >> On Wednesday, March 31, 2021 at 4:11:49 PM UTC-4 gregebert wrote: >> >>> Very interesting; thanks for posting. >>> >>> You might want to try successive numbers of lit cathodes, say 01, then >>> 012, then 0123, etc and see how the current increases, and also see if it >>> changes over time due to heating. >>> >>> I dont recall seeing this behavior with segmented tubes, like the 7971. >>> In fact, on my clock I have a current regulator on each cathode, and >>> another one for the anode, for every tube.....that works out to 128 current >>> regulators on that clock. >>> >>> On Wednesday, March 31, 2021 at 12:18:08 PM UTC-7 Bill van Dijk wrote: >>> >>>> Just a guess, but I think by lighting them all up you get some kind of >>>> “super ionization” in the tube, which could then increase the current and >>>> heat dissipation. >>>> >>>> >>>> >>>> Bill >>>> >>>> >>>> >>>> *From:* [email protected] [mailto:[email protected]] *On >>>> Behalf Of *Yohan Park >>>> *Sent:* Wednesday, March 31, 2021 3:15 PM >>>> *To:* neonixie-l <[email protected]> >>>> *Subject:* [neonixie-l] Lighting all digits at the same time: Why does >>>> this happen? >>>> >>>> >>>> >>>> I have a few Chinese QS30-1 tubes lying around which don't have much >>>> value for me and was wondering how it would look to have all digits lit at >>>> the same time. >>>> So I looked up the specs which say 170V and 2.25mA >>>> So I calculated the needed resistor to have it hooked up to 230V which >>>> is a little below 27K >>>> I then connected a 27K resistor to one cathode and it lit perfectly >>>> fine (230V AC so the anode also glows). >>>> So I then connected 10x 27K resistors to all the cathodes and plugged >>>> it in. >>>> Holy Moly! The thing lit up like crazy and was drawing over 9 Watts and >>>> was getting VERY hot. So I turned it off again after a few seconds. >>>> Can anyone tell why it's behaving like that? >>>> >>>> -- >>>> 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 view this discussion on the web, visit >>>> https://groups.google.com/d/msgid/neonixie-l/bffb114c-9810-4d65-8e98-ee13f6c860fcn%40googlegroups.com >>>> <https://groups.google.com/d/msgid/neonixie-l/bffb114c-9810-4d65-8e98-ee13f6c860fcn%40googlegroups.com?utm_medium=email&utm_source=footer> >>>> . >>>> >>> -- > 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 view this discussion on the web, visit > https://groups.google.com/d/msgid/neonixie-l/c8c35a61-fa0a-4249-9311-47061c50865cn%40googlegroups.com > <https://groups.google.com/d/msgid/neonixie-l/c8c35a61-fa0a-4249-9311-47061c50865cn%40googlegroups.com?utm_medium=email&utm_source=footer> > . > -- You received this message because you are subscribed to the Google Groups "neonixie-l" group. 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