GN-4 family : how do you drive the "hidden" points?

[Alic]

Hi,

I've seen pictures where the top of the "poles" (or however they're called?) which hold the digits are driven either together or one at a time.

Here is the GS-4 as an example : http://www.jb-electronics.de/html/elektronik/nixies/n_gs4.htm?lang=en

 

Has anyone seen a datasheet or other source on how to properly do this (current or resistor values, etc)? 

The datasheets I have seen don't mention this. Is it even supposed to be used like this?

Thanks for your help.

[jb-electronics]

I was surprised that this works when I took the pictures you referred to, but I am not sure if it is not mentioned somewhere. Jens

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[John Rehwinkel]

I suspect it isn't really supposed to be used like this, but I doubt it's harmful.

I'd probably drive them with some additional resistance (like decimal points), both to reduce the current to match the smaller lit area,
and to allow them to be driving simultaneously with a lit digit without "stealing" all the anode current.

- John

[Dekatron42]

In some nixie tubes like the LC-513 there is a dot to the left of the digits, see for instance here: http://www.tube-tester.com/sites/nixie/data/lc-513.htm , the LC-513A doesn't have this dot. However on a few of the LC-513 and LC-513A that I have the dot can light up on the right hand side instead or on both side, on some the supports at the top and bottom can light up if the "ic" (internally connected) pins are connected.

Driving the left hand dot on the LC-513 is identical to any other of the digits but in the few circuits that I have seen an extra cathode resistor has been used to limit the current, as in this datasheet for the LC-531: http://www.tube-tester.com/sites/nixie/dat_arch/LC-531.pdf (at 250V the anode resistor is 51k and the cathode resistor plus anode resistor is stated as 300k so some 220-270k can be used).

/Martin

[Alic]

Thanks everyone for the precious input!

Now I feel confident enough to start exploring on my own.
If I am able to drive both points of a GN-4(A) well, I can start my "universal display and clock" project with 8 nixies where the ones in position 3 and 6 can act either as "separator columns" in clock mode or normal digits in display mode.