Nixie tube without anode mesh

[q61org]

Recently I got hold of a nixie tube without an anode mesh, and thought it would be of your interest.

This tube, as seen in attached photos, completely lacks anode mesh in front of digits. Instead it has an unusual, oblong, oval shaped anode *between* cathodes, plus an upside-down 8 at about middle of the cathode stack (which I think is more common as an auxiliary anode). Since the anode is between cathodes, the frontmost digit 3 looks *very* clean when lit.

The type is JRC 4806. Quick googling did not yield any data or specs of this tube, but it looks like it is just one of many B-5991 compatible tubes.

I bought 6 of the same type but only one of them has this mesh-less configuration. Others have usual meshes that are similar to the ones B-5991 and 8422 tubes have. Also, digits in this tube have different shapes than the other tubes. I guess this is very old variant of this type of tubes.

I personally think this mesh-less configuration is better in terms of visibility of digits, but in reality almost all nixie tubes have anode meshes. I suppose this fact suggests that anode meshes have some advantages over mesh-less configurations. Can any of you suggest what the advantage would be? My twitter friend says anode meshes may give some stability when tubes are multiplexed. I'll give it a try, but I think there should be another reason(s) to describe why mesh-less is so uncommon. Any other thoughts?

ko

[MichaelS]

Hmm, interesting question.  Since meshless tubes tend to be older, I guess that people found that a uniform fine mesh was more readable than using another thick digit that would obscure the digits behind it.

Some tubes have a fine mesh that you can barely see and uniformly dims the digits, which our brains can process more easily than having several thick interference lines going different directions.  So, people can read the tubes further away.  Only Nixie addicts look at them up close & personal.  ;-)

Power considerations must have been a factor, too.  A meshless tube probably requires more power to run as the numbers get further away.

Many tubes had numbers stacked sequentially (0-9) but some had them carefully stacked to minimize how the front numbers obscured the back ones.  It makes a lot of sense when designing a display that can be read from far away.

It's probably why large tubes have an upside down eight as an intermediate anode and may be another reason why some biquinary tubes have an intermediate anode mesh.

It all just shows how designs improve over time and try different things along the way.  Pretty neat...  It's Nixie Evolution!  :D

[Alic]

Very interesting nixie!

I thought the primary reason for the mesh was to prevent the sputtering on the glass?

[MichaelS]

Ah, yes.  You must be right.  :)

You can silvering or darkening on used tubes where the mesh isn't.

[q61org]

Wow, yes, preventing sputtering on the glass seems to be the answer -- remembered I actually have some worn tubes that have heavy silvering only on parts of glass where their anode meshes have small openings. Those anode meshes really look like they do prevent sputtered cathodes to go through them (or do they absorb the sputtering?) 

(Now I'm curious whether my mesh-less tube actually goes dark and silver all over, but I don't dare to experiment it because I only have one...)

Thanks for all the inputs!

2017年2月13日月曜日 7時13分10秒 UTC+9 MichaelS: