Visually check to see if B7971 is dead?

[Robert]

Is that possible. Looking through some B7971’s and found a completely dead one, don’t remember buying a dead one, anyway visually looks okay, no broken stem or cracks.

Thanks
Rob

[gregebert]

Sometimes it's possible. I have 2 totally dead 7971's. One has a slightly visible crack at the base of a pin, so the gas is contaminated. The other one has no visible damage, and holding near a plasma globe has no effect, either.

[Robert]

I assume this one has failed near one of the pins

Rob

On 19 Jul 2025, at 15:15, gregebert <greg...@hotmail.com> wrote:

Sometimes it's possible. I have 2 totally dead 7971's. One has a slightly visible crack at the base of a pin, so the gas is contaminated. The other one has no visible damage, and holding near a plasma globe has no effect, either.

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[Adam Piórko]

I once tested a B7971 tube that seemed dead. After cleaning the pins with a fiberglass brush, it started working.

Adam

[Dekatron42]

I have a few where the thin metal strip connecting the Anode pin, with the thin glass tube surrounding it, having been blown off, only the welded portions are left on the pin and the Anode cage, everything else is gone!

I guess someone has tried to blow a short open and instead blew this thin metal strip like a fuse - bought the B-7971's from an eBay seller, who ofcourse didn't know anything, but eBay/Paypal refunded me in full. The same seller later sold fully working B-7971's he claimee but I steered clear of those auctions.

/Martin