NOS Nixie Lifetime

[Steve Scorn]

Hi group,

Does an unused NOS Nixie have a serviceable lifetime? I'm aware of cathode poisoning etc when powered on, but if correctly stored, would a NOS Nixie be just as good in 50 years as today?

Thanks for the help.

Steve

[Roddy Scott]

Hi Steve,

Considering that most of the NOS Nixies that we use range from 30 to 40 years old and are mainly reliable enough to last for about 30,000 hours using cathode poisoning prevention, I would not think that it would be a problem in general. 

Correct storage prior to acquisition would ensure a longer lifetime but if incorrectly stored this could lead to premature failure.

Most of the Nixies I have show some oxidation on the pins but it does not affect their performance. Cleaning this off, as mentioned in a previous post, could lead to the danger of the seal being compromised and this is the main thing that will make a tube fail or drastically shorten its lifespan.

I store my Nixies in bubble wrap and in a wooden box with dessicant 'pillows' which stops any moisture affecting them as Ireland is not the driest of countries! If you live in an arid area then the dangers from moisture are reduced. 

Like everything else, if you take care of it, it will last longer and this applies to Nixie tubes as well.

[gregebert]

My first nixie clock is built from tubes manufactured in 1963 (Burroughs 5092, my favorite). They were salvaged from a surplus RF generator I bought in 1975 (sorry, no pics but it looked & sounded awesome when powered-up), then sat in my open-air junkbox until 2011. Judging by the small amount of dust inside the RF generator, it couldn't have been powered-on for more than a few hundred hours, so these tubes are basically NOS. The clock has been in-service 24/7 almost 5 years now, with no hint of degradation. Of all my nixie tubes, this group of 6 is the only set for which I have solid historical info.

I've built 7 other clocks since then, with all sorts of tubes purchased on Ebay, and only 1 tube out of 55 has failed. 

[Walter2]

Nixies do have a lifetime (stored), but it expresses itself slowly. Mainly, loss of gas pressure, I see this effect most often in panaplex displays (which are actually glued together), and in russian tubes, which seem to have a poorer lead seal at the base.  In every box of 50 russian tubes, I generally find one that is totally dead.  US made tubes seem to fare better, but older types, like the 6844A are now at about 60 years old, and it is common to see low gas pressure in them.  the symptom is increased voltage to strike, and sometimes poor digit coverage on the larger cathodes, or in the extreme case, nothing happens.  I have often seen tubes 50 years old work perfectly, but equally, they also can be improved by cycling them through all the digits a few times.  Old used tubes are more problematic, any unused digits often are poisoned, and have to be carefully restored.  Like any "vacuum" tubes, their success is dependent on the quality of the glass seal, whether to hold in gas or vacuum.  rough handling of the leads or shock are the primary failure mechanisms to break the seal.

We have built a test jig to run and cycle all the tubes along with a variable supply and series resistor that runs up to 300V.  this allows us to find tubes with low gas, poisoned cathodes, base flash-over and other problems, plus it can be used to re-condition tubes and bring them back to optimal performance. I would suggest something like this if you intend to do a lot of nixie experimenting, as it allows you to really see the tubes work under different voltages and currents, and be sure the tubes are suitable before attempting a build. this is especially useful if the tubes solder in.

all the best,
walter  (sphere research corp)