Shorted GN-4

[Mac Doktor]

I have a GN-4 with an intermittent short between the 0 and 2 cathodes. It goes away when I tap the tube but it comes right back after a few seconds.

This is one of six tubes in a Systron-Donner counter. They're orange coated, no filter in front of them. It's working perfectly otherwise:

https://www.astarcloseup.com/2022/04/dawe-3001a-frequency-counter.html

Is there anything I can do? Does anybody have one on hand? The coating on them is in great shape.

Terry Bowman, KA4HJH
"The Mac Doctor"

https://www.astarcloseup.com

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

[gregebert]

First, measure the resistance with an ohmmeter. Most likely it's a metal whisker that grew between cathodes; I've seen this happen on multiple IN-1 tubes and I wont use those for any project.

If it's several ohms or more, you can try zapping it like a fuse by applying low voltage across it and slowly increase it till the short blows away. I recall seeing IN-1 "filaments" glowing around 50mA, and zapping after a few hundred mA.

[Peter Hall]

PV nixie has the GN4 for 11pounds

From🚨Peter Hall😁 insidiousnixies🦘Utube

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[Mac Doktor]

On Jun 8, 2024, at 7:50 PM, gregebert <greg...@hotmail.com> wrote:

If it's several ohms or more, you can try zapping it like a fuse

That old trick. I've never had to use it before. We'll see what happens.

Terry Bowman, KA4HJH
"The Mac Doctor"

https://www.astarcloseup.com

“...the book said something astonishing, a very big thought. The stars, it said, were suns but very far away. The Sun was a star but close up.”—Carl Sagan, "The Backbone Of Night", Cosmos, 1980

[andybiker]

I've done this once with a nixie which had two electrodes shorted with sputter and twice with dual-triodes in an amp where a whisker of grid had joined the anode.

I used a charged capacitor for the nixie and a motorcycle battery for the triodes....I was a student at the time and rode a bike!

A friend had a VFD with a similar problem - I told him this trick and it worked for him too.

I've done it on a membrane keyboard that must have grown whiskers and joined two elements.

It all depends upon the resistance of the short, whether you use a battery (low ohm) or a capacitor charged to 300v (high ohm)

If the short is caused by two numbers inside the nixie actually touching due to movement then you're out of luck.

Tapping or thumping may dislodge the short, current would only permanently weld the pieces together.

best of luck,

Andrew