B7971 with 2 segments lighting together

[Robert]

Hi

I have a B7971 where when the bottom left vertical segment lights the top left also lights

Is this a common issue?

Thanks
Rob

[Michail Wilson]

Not common, but if you look closely, you will see where the wire of the segment is overlapping the other.
You can smack it around to try to dislodge it, but at the risk of damage or breaking.

Over time, I've had 10 units with similar issues. I've been able to restore 8, but on 2 of them (1 I recently bought on ebay), I've separated them, but in doing so, one of the two segments would no longer light up as if the contact was bad from the start or disconnected during my smack around test.

Take a close up picture of the segments where they come close to each other. I have a couple I could upload before and after if interested.

Michail Wilson
206-920-6312

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[gregebert]

I've only had one tube develop a mechanical short between adjacent segments, most likely because they shifted and made contact. In my case, I was able to confirm this with an ohmmeter though I dont recall what the resistance was. 

Someone on this forum posted their fix for this a few years ago, basically attaching the tube to a stick, and whacking it. It might have been Michail Wilson; my apologies if I got the name/credit wrong. I'm way too much of a chicken to even think about doing this, so I keep this tube as a spare.

[Robert]

Thanks, that would be useful


Rob

> On 15 Jun 2024, at 16:24, Michail Wilson <M...@michail.com> wrote:
>
> Not common, but if you look closely, you will see where the wire of the segment is overlapping the other.

> To view this discussion on the web, visit https://groups.google.com/d/msgid/neonixie-l/SA0PR01MB6170F0193D549BE7FC942CE782C32%40SA0PR01MB6170.prod.exchangelabs.com.

[Jeff Walton]

Some narrative and photos for fixing mechanical shorts in the 7971. I've seen this primarily in the corners where segments at right angles have touched or overlapped.

https://groups.google.com/g/neonixie-l/c/w4YmXnY9dgE/m/8o-AsZZyBQAJ


Jeff Walton

[Robert]

My issue seems to be a bit different as it’s on segments 5 and 6, not on a corner, on the left hand side when looking at the tube

[Jeff Walton]

You probably have a different failure mechanism than the majority of the shorts that we have been able to deal with.   Depending on the type of tube it is (wire backplane vs PCB style), the failure mechanisms are potentially different.  If you see no visual evidence of a short near the pins, then you likely have an issue in the backplane.  Your photo shows good clearance of the cathode elements.  Have you checked the resistance between the segment pins? 

[Robert]

This is a PCB type

Thanks

Rob

On 16 Jun 2024, at 17:42, Jeff Walton <jwalt...@gmail.com> wrote:

You probably have a different failure mechanism than the majority of the shorts that we have been able to deal with.   Depending on the type of tube it is (wire backplane vs PCB style), the failure mechanisms are potentially different.  If you see no visual evidence of a short near the pins, then you likely have an issue in the backplane.  Your photo shows good clearance of the cathode elements.  Have you checked the resistance between the segment pins? 

On Sunday, June 16, 2024 at 10:45:12 AM UTC-5 Robert wrote:

My issue seems to be a bit different as it’s on segments 5 and 6, not on a corner, on the left hand side when looking at the tube

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[Leroy Jones]

I have a few el-cheapo type non-mercury Chinese nixies.   They are wire-ended, side view tubes.   Very nice-looking tubes

but very cheap construction.    Apparently, during manufacturing of these tubes at their dirty filthy factory, some random

junk gets in these tubes.   As a result, when they are laying on their sides in the box, this junk gets lodged between

digits and  causes shorts.    I have had real good luck clearing these shorts simply by holding the tube in my hand and gently

tapping with a finger while holding the tube at various angles.   This apparently dislodges the garbage and it falls to the bottom

where it cannot cause any shorts.