I've tried depoisoning a few of these 6844/5031 tubes with zero success, even at high current (20+ mA). They get hot, but wont clean-up. Whatever contaminates the surface of the cathode is rather stubborn. Perhaps it's an oxide; many of these failing tubes have a black haze inside the tube, which I suspect is Iron(II) oxide. There is a lack of oxygen, so the familiar Iron(III) oxide wont form.
On Saturday, April 27, 2024 at 1:19:52 PM UTC-7 Leroy Jones wrote: > Picture of clock built in 2010 that uses NL-6844A tubes. > > On Saturday, April 27, 2024 at 1:49:40 PM UTC-4 Leroy Jones wrote: > >> Hmm. This thread somehow got deleted. But anyway, as I was >> saying.....The National NL-6844A always tests better and with much more >> success than the Burroughs version ever does. >> These are certainly NOT ideal tubes. Short life. No mercury. But they >> do make up for their deficiencies by looking cool while they actually >> operate correctly. >> Especially on a clock that has them mounted on a clear case, and sticking >> out the front. -Chuck >> >> On Saturday, April 27, 2024 at 12:28:57 PM UTC-4 David wrote: >> >>> I have seen this also on these tubes. The 6844A is an early tube design >>> that didn't have mercury added to prevent cathode poisoning. I doubt that >>> anyone has done recent research on this phenomenon, so we're left with >>> conjecture. Here's mine: after the cathode gets poisoned, the plasma has to >>> be generated somewhere. That somewhere is the lead wires. Later tubes had >>> insulating paint applied to the lead wires to prevent this. It's usually >>> white or green. >>> >>> >>> David Forbes, Tucson AZ >>> >>> > On Apr 26, 2024, at 7:29 PM, Leroy Jones <leroypu...@gmail.com> >>> wrote: >>> > >>> > >>> > Hello, A while back I was testing a batch of Burroughs 6844A nixie >>> tubes. >>> > None in the batch worked correctly. Only the cathode lead wires >>> glowed, not the >>> > digits themselves. I have noticed this repeatedly on Burroughs 6844A >>> tubes. >>> >> -- You received this message because you are subscribed to the Google Groups "neonixie-l" group. To unsubscribe from this group and stop receiving emails from it, send an email to neonixie-l+unsubscr...@googlegroups.com. To view this discussion on the web, visit https://groups.google.com/d/msgid/neonixie-l/571f4cb9-40d4-4e7f-b5d1-8544b75d3569n%40googlegroups.com.
