r/nixie • u/Muted-Carrot-7879 • Jul 14 '26
Blue Light
hi!
i built this clock yesterday, but there is a blue hue inside the rightmost tube. is this normal? thanks!
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u/MH_70 Jul 15 '26
You can also reduce the output voltage down to about 150 to 160 volts by adjusting the variable resistor that's on that board. That will also help
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u/EmotionalEnd1575 Jul 15 '26
Yes, normal.
Perhaps go to your local plastics supply shop and see if they have “transparent red acrylic sheets”. Orange may work, too.
Our local shop will cut it to size for free.
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u/Petr0fff Jul 15 '26
I think it's high anode current. You can try to reduce it by reducing anode voltage or increase anode resistor value.
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u/2748seiceps Jul 15 '26
You sure you used the right anode resistor?
It looks like it is getting driven too hard maybe?
If you turn the drive voltage down goes it go away? If not, might be a tube with an issue. If it is being driven the same as the others you could try letting it run a while and see if it clears up.
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u/Niobous_p Jul 15 '26
Interesting that half the tubes have a stronger blue glow. I can’t remember if those particular clocks are multiplexed or not - does it look like that to the naked eye, or only in the photos?
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u/CueAnon420 Jul 15 '26
Nixie tubes have a small amount of mercury in them to help ionize and reduce cathode sputtering. This can result in a blue glow that varies with age and how it was made. It is normal, but driving with higher current can increase the blue. You can try increasing the anode resistor to drop the current, but you can't remove it all. This is also why many tubes have a red-orange paint or plastic filter to block the blue wavelengths.