[sdiy] Will Reverse Voltage Harm a Nixie Tube?

[KA4HJH]

>Yes, that's true, I'd venture a guess that if wired backwards, the common
>electrode will light instead of the numeral.

Something like that.

>However, either way will prove
>that the gas is still in the bulb.  Can these things fail other than by
>overvoltage abuse or gas leak-out?

Several ways. The cathode slowly loses its ability to emit electrons (or
quickly if you hit it with lots of current). The gas nuclei can be lost as
they zoom past the anode and embed themselves into the envelope. This is
called "hardening" and slowly reduces the volume of gas inside the envelope.

The Nixie is a fairly low current device so it should last a while but I
have no idea what the MTBF is. Properly made devices of this type (neon
signs, laser tubes, etc.) can have MTBF's of 10-20k hours or more.


Note that HeNe laser tubes are DC. Running them on a reversed potential is
NOT recommended since the anode is not designed to be an emitter. There are
also power supply issues with them because the cathode has a relatively
high capacitance AND the gas mixture has negative resistance. IOW, it will
"oscillate like a sieve" if you give it a chance.

-- 

Terry Bowman, KA4HJH
"The Mac Doctor"