IN-18 Going Bad

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4 years 3 months ago #7121 by Kpangon
IN-18 Going Bad was created by Kpangon
Hello,

I have a IN-18 Nixie tube clock from pvelectronics, and I believe one of my tubes may be going bad. The tube has suddenly started showing significant cathode poisoning on the 0,3,5,6,8,and 9 digits. This was very sudden, as I have the clock on my desk and I did not notice any poisoning yesterday. Almost 50% of each affected digit will not illuminate, so I'm confident I would have noticed it yesterday.

The clock has been running continuously for over a year, and has shown no problems until now. It shuffles the digits for 5 seconds every minute. All the tubes were from the same batch, but it is only one tube that shows any cathode poisoning. The tube is in the hours position, so every digit gets equally used.

I removed the tube, and used the Nixie tube tester I have to "burn" off the cathode poisoning from the affected digits. It came off very quickly, and each digit illuminated perfectly after only a few minutes of baking at 8ma. I reinstalled the tube, but after a few hours the cathode poisoning is starting to return on some of the digits.

Is there any hope for this tube, or should I just install a new one? What could cause a tube to fail so suddenly? How long have you all had IN-18 tubes run before they fail?

Also, the tubes are dated 12/84. They have been run at 180v and a current of about 4.5ma.

Thanks

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4 years 3 months ago #7122 by lcc
Replied by lcc on topic Re: IN-18 Going Bad
HI have you tried it in a different position in the clock just in case there is a fault on that part of the circuit which PV kit is it the new spectrum or the old version? always worth a look at solder joints i know you said it being ruing for 12 months but could be a dry joint playing up

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4 years 3 months ago - 4 years 3 months ago #7123 by Kpangon
Replied by Kpangon on topic Re: IN-18 Going Bad
Yeah, I moved it to a different position, and the cathode poisoning still came back after a few hours. Its the new Spectrum 18 kit. All the solder joints appeared to be good when I inspected them with my loupe. One of the other tubes is starting to show some cathode poisoning as well, so I think these tubes might just be reaching the end of their life. It's a shame since they are only just over one year old.

The only thing that is strange is that the cathode poisoning comes off very easily, even during the normal operation of the clock. For example the "8" cathode will have have cathode poisoning, but within several minutes of operation it will resolve itself. For example, when it changes to 8:00 the "8" will show significant cathode poisoning, but by 8:05 it will be fully illuminated. By the time the next 8:00 rolls around the cathode poisoning will be back.

I'm going to put a new set of tubes in the clock, and if the the cathode poisoning shows up on those as well then there may be something wrong with the clock.

I took a video showing just how quickly the cathode poisoning resolves itself. you can see it on the 0,6,7,and 8 digits.
Last edit: 4 years 3 months ago by Kpangon.

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4 years 3 months ago #7124 by lcc
Replied by lcc on topic Re: IN-18 Going Bad
HI
have you had a word with Pete at pv as the spectrum kit is direct drive in stead of multiplexing so should prevent cathode poisoning it could be a part of the power supply failing in the clock the only time i had a problem with a IN-18 tube was when it had being stored for a long time and i used a nixie tube tester too restore it and it was a good 24 hours to get it good again its a lot of money to put a new set of tube in if it turns out to be a failing component in the clock i am only a kit builder so the technical side of the operation of the clocks is beyond me
steve

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4 years 3 months ago - 4 years 3 months ago #7125 by Ty_Eeberfest
Replied by Ty_Eeberfest on topic Re: IN-18 Going Bad
Watched your video and I'm not so sure that what I see there is actually cathode poisoning in the usual sense. I've seen something like that before and the cause was not the tubes, it was caused by the high voltage being just a little bit low (can't remember how many volts low anymore but it wasn't very much). Not all tubes were equally affected, probably because of "tolerances" in manufacturing.

Look into it later when the dust is clearing off the crater.
Last edit: 4 years 3 months ago by Ty_Eeberfest. Reason: Typo

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4 years 3 months ago #7126 by Kpangon
Replied by Kpangon on topic Re: IN-18 Going Bad
I thought it might have something to do with the voltage as well, but the power supply is putting out just over 180 volts with all 6 tubes running. I'll send Pete an email and see what he thinks about it.

I'll see what happens to the new tubes I put in it. I've got a bunch of IN-18s stockpiled, because I was afraid they would go up in price as they become more difficult to find. Its a good thing too, when I bought them they were just under $200 for a set of six, and now they are well over $300 on ebay.

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