Touch sensitive Nixe?

[Paul Parry]

Hi All,

Just assembling a clock, and I have an intermittent nixie tube ( Rodan GR116's ) that flickers and will not stay on. However just touching the tube with a finger makes it work so assume it is some strange capacitive effect.

I am not over driving the tube ( 170v ) and a 10K anode resistor - altering these + / - 10% does not really improve things.

I have several of these tubes, half work fine and other half all have this strange effect of working when touched. I know all the tubes are 'ok' as they came from a frequency counter that I powered up and saw them all working before I carefully removed the tubes.

Any suggestions appreciated.

Cheers,

Paul

[threeneurons]

Raise the supply voltage to 180V, and see what happens.

[Charles MacDonald]

> Just assembling a clock, and I have an intermittent nixie tube (
> Rodan GR116's ) that flickers and will not stay on. However just
> touching the tube with a finger makes it work so assume it is some
> strange capacitive effect.

Not all that strange, Florescent tubes that are on their last legs will
sometimes start if you rub your hand along the length of the tube.

Same principle as those Elevator floor number Gas tubes that lit up (and
sent a signal) when you touched them.

--
Charles MacDonald Stittsville Ontario
cm...@zeusprune.ca Just Beyond the Fringe
http://Charles.MacDonald.org/tubes
No Microsoft Products were used in sending this e-mail.

[Paul Parry]

Many thanks for the advice,

 

I raised the voltage to 180v and the tube seemed to behave more like I would expect and at 190v was ok. However the other tubes in the multiplex developed a hazy pink glow so I quickly turned the voltage back down. I can only conclude that the tube is on its last legs and I would never use anything even remotely suspect so I've binned it.

I had another tube that for some reason the bottom half of the digit would not light, is Neon lighter than air and just risen to the top of the tube?

 

Cheers,

Paul

 

[Jon]

If that were the cause, then I'd recommend a vigorous shake to remix the gases :)  Seriously though, the contents of your tube are 98%+ neon, with the balance being argon and possibly a trace of mercury vapour. No air of any description in there, else it wouldn't glow at all under the voltage applied in your circuit.

More likely what you're looking at is a phenomenon called cathode poisoning, where tubes unused for a long time seem to pick up a surface contamination of some parts of the cathode which inhibits the glow. Try running the tube at 1.5 or 2x normal current for a while and see if that clears it up.

Cheers,

Jon.

[petehand]

You should probably un-bin it and run it for a couple of days before doing anything so rash. I brought up a set of B6091s this week that had been sitting in a box for years. One of them worked. On the others, some cathodes wouldn't light, some struck at the pins but not the numeral, one wouldn't work at all - I finally got it to light just the '1' cathode by zapping the envelope with my wife's tazer. All of them flickered. I left them on overnight and 24 hours later, all work, all cathodes, no flicker.

[Paul Parry]

Un retrieved from the bin, I've got about 8 of them in total that I'm not happy with.

 

I will put them on soak, with a higher anode current and see what happens. I don't have a tazer lying around though! can't go to Tesco's and get one LOL

 

Cheers,

Paul