Silver coating on inside of glass

[alex nolan]

Hey all,

Has anyone seen a tube with the inner glass covered in silver spots inside the tube? What does this mean and is it repairable like cathode poisoning?

Thanks!

[Dan Hollis]

Is this different from the usual getter spots?

-Dan

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[Dan Hollis]

Was showing a friend the movie 2001 for the first time, and noticed nixies in one shot:

http://3.bp.blogspot.com/-0X7Adbhg1DA/UFCJSxQZugI/AAAAAAAAA04/HSOQwLM5vIo/s1600/nixie+2001.jpg

-Dan

[Kevin A.]

That could be mercury condensate. I've seen it on a few JAN (mil spec/extended life) nixies I have; mercury is used to greatly reduce cathode poisoning. 

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[Bill van Dijk]

Are we talking about a regular (non nixie) tube? The cold 866 rectifier tube for instance has a lot of condensed mercury on the inside of the glass. It evaporates when it gets hot.

 

Bill

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[gregebert]

I tried heating one of my tubes with this shiny interior coating, and it would not turn to gas. The pressure inside a nixie is fairly low, so I thought that if this was mercury, it should have boiled-off, but it didn't. Perhaps it is a different metal; I'm not going to break it open to find out.

On a similar note, I have some tubes with a black interior coating that wont budge with heat.

But, I did watch one of my 6091's at normal operating temperature with grayish internal deposits and saw the metal, presumably mercury, slowly evaporate. It probably condensed elsewhere.

[alex nolan]

This is a nixie tube, specifically a B-5441. It looks like there is some trouble getting the cathodes to fully light and it is missing the blue haze around numerals that other B-5441s seem to have.

[Mac Doktor]

On Apr 10, 2019, at 7:59 PM, Dan Hollis <parkxz...@anime.net> wrote:

Was showing a friend the movie 2001 for the first time, and noticed nixies in one shot:

http://3.bp.blogspot.com/-0X7Adbhg1DA/UFCJSxQZugI/AAAAAAAAA04/HSOQwLM5vIo/s1600/nixie+2001.jpg

There are lots of Nixie shots in Earth II:

https://en.wikipedia.org/wiki/Earth_II

https://www.youtube.com/watch?v=9xPMUFywjDw

I saw it when I was ten years old and I'll never forget those cool numeric displays. They really stuck in my mind.

Terry Bowman, KA4HJH
"The Mac Doctor"

"If only you could see what I've seen with your eyes."—Roy Batty, Blade Runner

[Mac Doktor]

If you're a fan of 2001: A Space Odyssey I highly recommend Cinema Tyler's documentary series on the making of the film:

https://www.youtube.com/results?search_query=cinema+tyler+2001

There's a lot of stuff in there that I didn't know.

[Kevin A.]

If you could take some pictures that would be helpful.

On Wed, Apr 10, 2019, 9:28 PM alex nolan <masterscri...@gmail.com> wrote:

This is a nixie tube, specifically a B-5441. It looks like there is some trouble getting the cathodes to fully light and it is missing the blue haze around numerals that other B-5441s seem to have.

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[jb-electronics]

Alex, from what it sounds like it could be so-called "sputtering." This is when over years of use some of the cathode material (the digits, which are constantly bombarded by ions) detaches from the digit and flies around in the tube. Usually it deposits on the inside of the glass bulb, and from the outside it looks like a shiny silvery coating, just like you describe. There is nothing you can do against it, it is a sign of wear on any tube.

A picture would help to make sure it is indeed sputtering :)

Best wishes
Jens

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[Bill Notfaded]

I think Jens is right... usually that means the tubes are hit ie. pretty much ruined.  I took a bunch of old frequency counters and old mulitmeters apart recently and some of them had this condition.  I'm sure many stayed turned on set on single digits for hours at a time and just got worn out.  Some of the devices tubes were fine... some had almost all the tubes with that silvered on the inside of glass in front of the cathodes problem.

Bill 

[Mac Doktor]

> On Apr 11, 2019, at 1:23 PM, Bill Notfaded <notf...@gmail.com> wrote:
>
> I think Jens is right... usually that means the tubes are hit ie. pretty much ruined. I took a bunch of old frequency counters and old mulitmeters apart recently and some of them had this condition. I'm sure many stayed turned on set on single digits for hours at a time and just got worn out. Some of the devices tubes were fine... some had almost all the tubes with that silvered on the inside of glass in front of the cathodes problem.

Same here. I have several pieces of test equipment with six or eight tubes that are virtually opaque in the first decade and fine in the last two. Each decade has a different brightness.

[【ツ】John Smout]

I have a bunch of used panaplexes with silvering hotspots. Not much I can do but laugh…

John S

[gregebert]

So it looks like the cathodes are poisoned (dark areas), and where they are still glowing, the metal has deposited nearby.

I wonder if you can depoison them with high current, and coax the metal to redeposit at the bottom of the display by leaving it vertical, where the temperature is lowest.

[Bill Notfaded]

It's almost like borderline Predator movie alien display characters now!  :^}

[Bill Notfaded]

https://www.blendswap.com/files/images/2012/09/blend_54270/metalhead_alien_wrighting_screenshot_medium_9a63adaecfcdf33437c60b24dcb8f4d3e3398182.jpg