Nick,
I hear that too low of a current can cause other problems with
sputtering and cathode poisoning.

On Mar 9, 4:57 am, Nick <[email protected]> wrote:
> On Mar 9, 8:46 am, "JohnK" <[email protected]> wrote:
>
> > How about you check the tolerance % of the resistors.  Did you use 10%, 5%
> > etc  ?
> > And, how about you measure the voltage drop across each of the anode
> > resistors in turn.... and with different digits ON.
>
> > BTWQ, that current increase is not large.... BUT, it may not be spread
> > evenly across the tubes; what if it is one tube drawing all the extra?
>
> Further to that - accurately measure each anode resistor, then measure
> the voltage drop across them, then for each work out the current - you
> should probably use a BIG digit, such as "8" to do this.
>
> Generally, the life of a nixie exponentially decreases with increased
> anode current. I would probably aim for an average of 2mA per digit,
> and 1.5 may be enough, i.e. always err on the low side.
>
> Bear in mind that this is NOT precision science. 10% or worse
> resistors were commonly used, and the characteristics quoted for tubes
> are really an idealised average over a sample.
>
> Note that the current requirement for a given level of illumination is
> related to the surface area of the digit. Some tubes are cute about
> this and make the "1" fatter and the "8" skinnier etc. to compensate,
> but this is not always the case.
>
> So, relax a bit, aim for about 2mA or a bit less, and stick with that.
> Note the decimal point is max rated at 0.3mA
>
> Nick

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