Relocate tubes on single clock

[Forfanatic Tsai]

Hi, sorry this might sound like a noob question.....

Will you relocate tubes on a clock? like switch second tubes with hour tubes for balancing life time. Or just left them there until they fails?

I own one Spectrum 18 from PV electronics now and IN-18 price is flying high now :( (sure I won't care this if it's a set of cheap IN-12s lol)

[Jeff Walton]

It will depend on who you ask, so be prepared for opinions and reasons.  We all value the tubes highly and try to do whatever we think will prolong and extend their lives.  Keep some spares for a rainy day…

 

I would have no problem moving them around (that’s my comfort level) but the cathode poisoning prevention routines are supposed to help prolong the usable life of the tubes.  Even within a single tube, you might normally observe small variations.  You only run the risk of damaging the pin seals to the tubes by physically moving them around.  Careful handling and straight pins will reduce the risk.

 

One widely used practice for tubes that are used, is to place any tubes that have weak digits (other than 1 and 0) in the tens of hours position because that position uses the least of the digits on a regular basis.  The tens of minutes and the tens of seconds are the next “hiding place” for tubes that have weak upper digits.  Only the seconds and minutes positions are evenly used in the conventional six digit clock.

 

I have one nixie clock that ran for over 35 years without a tube failure (CK8754 tubes).  I think that the overall brightness was slightly lower after all of those years but they faded together.  The tubes were never rotated and in fact, the pins were soldered to wires in the perf board  with point-to-point wiring.  They were direct drive at rated current.  While these tubes were not IN-18, I think that nixies, if driven within spec using modern designs and cathode poisoning prevention, can expect a decent life.  The Spectrum clocks have cathode poisoning prevention and currently feature a PIR motion sensor that will extend the life of the tubes when no one is around.  I think that using the PIR feature will have more of an overall life extending effect than moving the tubes around.

 

Jeff

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[Forfanatic Tsai]

Thanks Jeff, I do have PIR sensor installed...guess I better don't mess them around lol

[Kyle Jones]

When you really think about it moving them around not only risks breaking them but can cause multiple tubes to have uneven wear vs just a couple. The 10s hour spot only does 0, 1, and maybe 2 so you end up with the most time on those digits. Move that tube to the seconds where it gets equal time on each and you still have more time on those first digits but after a while they'll start to look dimmer than the larger numbers.

Not sure how many examples of worn out IN-18s there are on the forums here. Probably WAY more gas seal breaks than worn out mercury spiked nixies.

[Jonathan Peakall]

I agree about breaking 'em and uneven wear, and the digits that get
cathode poisoning aren't getting used, so who cares?

I was tinkering around on the code for my oldest clock and checked the
hours tube. Couldn't see any difference after 15 years of operation. The
first 9 years it was on 24/7. The last six it has had a motion sensor on
it and only runs with someone in the room. These are B5991 tubes.

Jonathan

[Alic]

I don't own a nixie clock long enough myself, but I've heard of several examples of nixie clocks running for a long time where the tube of the 1st hours digit had to be replaced. It seems that no cathode poisoning prevention was used back then though.
The future will tell which of the current life prolonging measures is the most efficient.
Turning the nixies off when nobody is looking seems to be the obvious choice.
Now all I need is to find a way to hide that ugly PIR sensor ;-)

[Jonathan Peakall]

Alic,

Cathode poisoning only affects the unused digit. So it isn't a reason to
replace a tube, as the affected numbers are never used. The only time I
could see it being an issue is in the hours tube that you might go from
displaying civilian time and then you want to display military time.

I remotely located my PIR sensor so it is hidden and in a good position
to detect people. So I do have a wire leading from the clock but at
least don't have the sensor sitting like a wart on the clock. It makes a
great night light, off when you don't need it, on wen you do!

Jonathan

[Alic]

I thought that there was actually an exchange of matter between the cathodes going both ways when all the cathodes are on alternatively.
Which means that if only 1 or 2 cathodes are used, theses cathodes erode faster.
I don't know if the sputtering on the glass in the front is also worse on the first hours digit?

But I also understand that the lifespan of a nixie is mostly a sum of the lifespan of each cathode.
In some datasheets you can find the lifespan if only 1 digit is used or if the same digit is on for a long time (the datasheet I just found says every 100 hours though...). Page 6 of the PDF from Telefunken for example :
http://www.tube-tester.com/sites/nixie/dat_arch/Telefunken_01.pdf

Perhaps the cathode poisoning prevention can prolong the lifespan a little, but the first hours digit will inevitably fail first simply because in every case the same 1 or 2 cathodes are on much longer than the others.

So for me the question remains.
Let's say there is a way to switch the position of the nixies without risk, by moving them with their sockets for example :
Is it better to change the position regularly and have the 0s and 1s fail (much?) later but on all nixies more or less at the same time, or is it better to "sacrifice" one nixie, knowing that it will have to be replaced much more often?

[A.J. Franzman]

On Thursday, June 2, 2016 at 11:43:26 PM UTC-7, Jeff Walton wrote:

From: neoni...@googlegroups.com [mailto:neonixie-l@googlegroups.com] On Behalf Of Forfanatic Tsai
Sent: Friday, June 03, 2016 1:08 AM
To: neonixie-l
Subject: [neonixie-l] Relocate tubes on single clock

 Will you relocate tubes on a clock? like switch second tubes with hour tubes for balancing life time. Or just left them there until they fails?

 

 

I would have no problem moving them around (that’s my comfort level) but the cathode poisoning prevention routines are supposed to help prolong the usable life of the tubes.  Even within a single tube, you might normally observe small variations.  You only run the risk of damaging the pin seals to the tubes by physically moving them around.  Careful handling and straight pins will reduce the risk.

I seem to recall discussion in the old Yahoo NEONIXIE-L of a U.S. Army report that scheduled monthly testing of in-service vacuum tubes (necessitating their removal from equipment) caused such a service-wide statistical increase in tube failures that the practice was largely abandoned; for most purposes it was deemed not worth the cost to have them fail more often (or be discovered to be about to fail) during scheduled downtime, than to simply let them fail whenever they happened to do so. I searched in the archive some but couldn't find the thread... does groups.io have an "Advanced Search" feature?

 

On Wednesday, June 8, 2016 at 8:37:03 AM UTC-7, Alic wrote:

I thought that there was actually an exchange of matter between the cathodes going both ways when all the cathodes are on alternatively.
Which means that if only 1 or 2 cathodes are used, theses cathodes erode faster.

There is definitely an exchange of matter, but that may or may not be a good thing. In mercury-doped tubes, presumably it is a good thing to return some mercury to the "off" cathodes from the presently "on" cathode, but I'm not sure the equivalent is true for non-mercury tubes.