IN-16 without Neon but with Argon

[Paolo Cravero]

Hello.

As I said in the IV-6 thread, I bought some apparently dead IN-16 that react to a Neon tester (HVAC) with a violet/lavender glow.

Since there is gas, it will light up one way or another!

This is the promising result with 632 Vdc at about 9 mA: https://youtu.be/NfKj6_Kf8DE (color does not match reality).

To me it looks like a normal Nixie at undervoltage conditions. I can probably add some other 100V using battery powered DC-DC boosters.

Paolo

[gregebert]

I still think the tube has leaked. 600V is a lot of voltage, and it's going to get pretty warm at 9mA.

From Paschen's curve, the ionization voltage is at a minimum at a certain pressure, around a few mBar. At pressures above AND below that point, the ionization voltage increases. As a tube leaks, it's pressure increases as atmospheric gases leak in and that will increase the ionization voltage and change the spectra.

[Christian Riise Wagner]

That's pretty cool that it somewhat lights up. However I think that you're mistaken in your assumption that the neon has escaped, leaving only argon in there. The gas mixture in a Nixie tube is at a very low pressure, so my guess is that atmospheric air has leaked into the tube, thus increasing the pressure inside. This would also explain why the voltage needs to be that high. And ionized atmospheric air does indeed light up purple.

[Paolo Cravero]

Hello.

I was wrong on the leak direction, indeed. I did further experiments with the couple of tubes that react to the neon tester (HVAC source applied to one pin, and holding the tube with the other hand).

I could pile up power supplies to just below 700V and digits still don't light fully. Given its small surface, the decimal point always works. The voltage drop in the tube is between 350 and 390V depending on the current. At 9mA it gets warm to the touch. Pleasantly warm, could be 35°C (+15°C from room T). Then I tried again 630V @ >=4mA and it is still possible to get a glow with the 350V drop. The nice thing is that the glow constantly moves up and down the digit, therefore with a proper power supply it could be used in some art display. Colour changes with current.

It has been a nice practical learning experience.

Paolo

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