Tube starts to fail

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6 days 22 hours ago #12704 by jjansen
Tube starts to fail was created by jjansen
Hi,

I have the modular Nixie clock (IN 14 tubes).
Running for 2 years now without any problems.

Last week, during a holiday, I turned the power off for 1 week.
After connecting the power again, the second indicator tube started to fail.

It does not light the complete number. Some numbers do not light at all. It is also a bit less bright (orange) compared to the other tubes.

See pictures at
imgur.com/a/LlRI9Lz
(taken while executing the tube repair routine; no effect)

Any idea what the problem might be?

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6 days 21 hours ago #12706 by Ty_Eeberfest
Replied by Ty_Eeberfest on topic Tube starts to fail
Seems like you have only 2 possibilities: either the tube itself is going bad (it happens) or the anode drive optocoupler for that position is failing. Since you have the Modular it should be easy to swap the offending tube to a different position to see what happens. If the problem stays with the position then the opto is bad. If the problem moves then the tube is bad.

Look into it later when the dust is clearing off the crater.
The following user(s) said Thank You: jjansen

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6 days 31 minutes ago #12708 by jjansen
Replied by jjansen on topic Tube starts to fail
Opto coupler is ok. So should be a bad tube
Strange that it happens after a week without power.

Might increasing the voltage help?

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5 days 22 hours ago - 5 days 14 minutes ago #12709 by Ty_Eeberfest
Replied by Ty_Eeberfest on topic Tube starts to fail
I suppose you could try increasing the voltage a little bit but if you increase it very much it will shorten the life of the 5 good tubes pretty severely. I would not recommend going any higher than 180V.

I have no idea why the problem would appear after a week of being powered off.

Just FYI - the "tube healing" mode will only fix one type of problem: cathode poisoning. Looking at the photo you linked I see the bad tube is in the1-sec position. In that position all 10 digits are used equally and cycled rapidly, thus cathode poisoning is highly unlikely to occur, A more likely failure mode in your case is a loss of gas, It happens sometimes, for no obvious reason.

EDIT: Not really a loss of gas but more like a gradual incursion of air, which dilutes the neon gas and increases the pressure (reduces the vacuum actually) inside the tube.

Look into it later when the dust is clearing off the crater.
Last edit: 5 days 14 minutes ago by Ty_Eeberfest.

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5 days 2 hours ago #12714 by Ian
Replied by Ian on topic Tube starts to fail
The only reason I can imagine that it happened after a week being turned off is that everything cooled right down and perhaps the thermal cycling was the straw that broke the camel's back... Unlikely, but the only thing I can think of.

There is also the factor that tubes can absorb a small amount of gas until the getter is exhausted, so it might have been that there is a slow leak for some time, and now the gas in the tube is reaching the critical level. Were there any drops or shocks in the previous weeks or months?

Tubes are unfortunately to some degree "consumables". This was one of the reasons why the Modular was made - I have spare tube holders and if you contact me off-forum, I'll send you a replacement or two.

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4 days 20 hours ago #12719 by jjansen
Replied by jjansen on topic Tube starts to fail
Hi Ty and Ian,

Thanks for your responses! The possible causes sound logical.
(btw. no drops / shocks in the previous weeks/months).

No problem to change the tube, that's also why I liked the modular design! I will contact you (Ian) off-forum.

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