sale or trade- B7971 2.5" 17-segment nixies

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8 years 11 months ago - 8 years 11 months ago #2079 by zzf7a55434
:whistle: ..and it's back to the pair of spares. the 8-pack probably ships out tomorrow. Sorry, all. I'm crossing my fingers for one more find, even if just 6.

And I should have said yes, I do have a junk pile on steroids, just most of it is 15 miles away. video games, pinballs, parts, S-100 computers, and god knows what else.

I built the lighting supply and backup in a spare mini-AT computer case hanging on the wall here in the computer room, the original p/s (removed the fan- but also the upper housing) supplies the AC-on 12.4v, and plenty of room for relays, battery, charger, 6 'zone' switches individually fused, etc.

BTW, if anyone wants a fairly inexpensive but super wide function DVM- hit eBay and search for the VC-99 from Vichy.

Cat II 1000v insulated, 3-6/7 [6000 count] 1" display with analog bar, AC/DC v to 1000v, AC/DC current to 10A, resistance to 60 megohms, auto-discharge capacitance to 2000 microfarads, frequency to 60 mhz, duty cycle 1-99%, transistor hFE test, comes with a 1000 degree c temp probe. Kicks the tail off my old Fluke 77 mk. 1.

Bob McMains,
broken joat
Last edit: 8 years 11 months ago by zzf7a55434. Reason: idiotic spelling errors.

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8 years 10 months ago #2313 by zzf7a55434
for the present i have no tubes for sale- the pair of high-production era burroughs B7971's went to merry olde england a day or so ago.

I''m hanging on to the one early low-production 'antenna' burroughs with hand-placed nickel ribbons to the segments and slightly taller glass envelope as a keepsake.

has anyone else looked close enough through the lower mica back of the display to see the wire-wound captive dark blue glass bar held to the base of the B7971's?

pictures available on request at This email address is being protected from spambots. You need JavaScript enabled to view it.

Bob McMains,
broken joat

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8 years 10 months ago #2342 by Stuckey
Hello -
I looked though some of the tubes I purchased from you and I actually can't the blue glass. Was it only on all of the tubes with the antenna?

"If the laws of physics don't apply in the future, then god help you."
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8 years 10 months ago #2343 by Stuckey
Wait, I spoke too soon. I see what you're talking about. What purpose does that serve?

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8 years 10 months ago #2344 by zzf7a55434
Replied by zzf7a55434 on topic little glass bar
I'm not sure exactly what they used this for, but probably to either scavenge gases not desired (in vacuum tubes, they fired a 'getter' charge to remove the last traces of oxygen) or to add the trace of mercury or whatever ionization assistance element they added to the neon to avoid having to have a separate anode for each segment, by 'boiling' it out of the glass to avoid exposing the workers on the production line.

one of the last tubes [later production series] I sold the bar had come loose- one of the 2 attached pix shows it, and if you look at the main pin to the left of the bar you can see one end of the heating coil welded on the side.

just another detail that has escaped notice to this point, I guess.

Bob McMains,
broken joat
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8 years 10 months ago #2347 by AnubisTTP
Replied by AnubisTTP on topic Re: little glass bar
The little glass pill in some higher end Nixie tubes is called a giver, it's used to add mercury to the tubes to extend the lifespan. The glass pill is filled with mercury and after the tube is sealed and pumped down, the manufacturer heats up the coil around the pill to melt the end off and release the mercury into the envelope.

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