Gassy Nixie Tubes

[pentium]

Picked up a Heathkit DMM with two Nixie tubes in it. One (seen left) was fine but the other (seen right) has developed a shiny coating in front of the digits which makes it hard to read.



I have seen this before on tubes but it was normally around the getter which is nowhere in the area.

[japlytic]

Re: Gassy Nixie Tubes

I've seen neons (about the size of the NE-2 type) have a silvery coating.

[Marsman]

Re: Gassy Nixie Tubes

The silvery coating in most vacuum tubes is caused from the small bead of mercury that is placed inside during the evacuation and sealing operation. When the heating coil in the tube is energized the mercury will vaporize and burn off or trap any impurities left inside. Where and how the mercury deposits on the glass seams to be random. My guess would be that the film was always there and that the tube is starting to get weak and therefore not showing through as well.

[Agent24]

Re: Gassy Nixie Tubes

Assuming this is correct: http://en.wikipedia.org/wiki/Getter

The little ring at the top is a flashed getter, and the deposit is normally next to it. (or is at least in all the tubes I've ever seen, then again that's not many) Why yours is on the side doesn't seem to make sense.


However, what I have noticed is that my old torch bulb for my Maglite turned silver (almost black in fact) completely over time. Maybe your problem is something similar, and not the getter at all?


Edit: This sounds like your problem:

Nixie tubes are susceptible to multiple failure modes, including:

• sputtering of electrode metal onto the glass envelope blocking the cathodes from view

(http://en.wikipedia.org/wiki/Nixie_t...s_and_lifetime)

[kc8adu]

Re: Gassy Nixie Tubes

the one on the right is just worn out.lot of hours on it.