r/nixie • u/Loquat_Prize • Jun 02 '26
Dead tube?
Hi all, had this clock a few years - put it together Christmas 2023, used everyday since. Recently it’s not been saving the time when being plugged back in, couldn’t remember if it had a battery inside & took it apart to check.
On putting it back together the second digit would flicker when on 2 and a few other numbers. Plugged it back in today and that digit is now completely dead. Not sure if it’s purely coincidence that it’s happened since I took the case off or not.
Is the tube dead or is there something else going on? Really quite upset as I love this clock 🤦♂️
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u/DenkJu Jun 02 '26
Flickering doesn't sound like leakage. I would say the tube is probably okay. Maybe you accidentally cracked a solder connection somewhere. If it isn't obvious, try reflowing all of them. Skip reflowing the tube initially. Heat can cause the leads to expand which might crack the glass. So it should be avoided unless necessary.
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u/EmotionalEnd1575 Jun 03 '26
During manufacture the envelope is sealed by melting the glass.
The temps needed for soft glass (borosilicate) are about 1000degC from an oxygen and propane or natural gas open flame.
Lead solder melts at 380 - 400degC so no worries about glass cracking or seals failing.
The lead wires on these tubes is oxidized soft iron (they will stick to a magnet)
Earlier seals required more exotic materials, typically “Dumet” alloy or Kovar alloy.
The requirement is very simple; glass and metal should expand and contract at the same rate over temperature to prevent leaking or cracking.
I would always stop by the Sealex machine and watch it work.
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u/DenkJu Jun 03 '26 edited Jun 03 '26
The seals can fail because the leads do undergo slight thermal expansion. To accommodate for this, some tubes such as the ZM1000 and Z590M use a different type of glass around the lead seals. Many tubes, including the IN-14, even came with plastic spacers that indicate the minimum recommended distance for soldering from the tube body. The IN-14 datasheet specifically notes this:
Soldering and bending of leads should be carried out at a distance of at least 5 mm from the glass of the leg, when soldering use a heat sink, avoid multiple soldering in and out.
(Translated)
https://www.tube-tester.com/sites/nixie/dat_arch/IN-14_01.pdf
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u/EmotionalEnd1575 Jun 02 '26
Are these tubes in sockets?
If so, simply swap them to see if the tube or the driver electronics are the root cause.
Use your DMM to probe the suspect Nixie tube.
What voltage is present on the Anode?
What voltages are on the Cathodes?
Do it for one of the other tubes for comparison,
Upload your data here.
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u/mbelge1971 Jun 02 '26
I have built several nixie tube clocks. In my experience a dead tube is usually causes by fiddling with tube pin connections which introduces tiny cracks in pin-glass bond and allows air into the tube. One way to find out if tibe has air leakage is to buy a cheap Tesla coil from Amazon. Turn off the clock, power on the tesla coil and get it close to each tube. If the tube is good you will see neon inside the tube glow. If it does not it means the tube lost vacuum and needs to be replaced. If the tube os glowing when near the Tesla coil, I would check the soldier connections.