Thank you for the responses so far. What interests mwe the most about
all of this, is that this is making me wonder exactly what it is
that determines initially when the tube is brand new, the difference
between the bond wires and the actual digit cathodes. Upon close
examination of these dud tubes, and a known good working one, I can see
no obvious difference between them. Looking closely, I see that the
bond wires run very closely to the outside of the cylindrical shaped
anode. It makes perfect sense to me that these wires be surrounded with a neon
glow, simply because they are so close to the anode. I want to know
what the tube designers did to prevent this glow, and why it is happening now.
In other words, what exactly has happened to these tubes from sitting
in their boxes since 1968, which would make the wires glow
now, yet they did not glow whehn the tubes left the factory. Or
possibly this was a defective batch that was never any good from day 1.
I suspect that they have leaked. Something is probably up with the
internal pressure, and/or the gas mixture. Perhaps some air got in.
Not enough to completely kill it, but enough to cause this highly
abnormal behavior. I bet Dalibor might know. Perhaps I'll contact him and
attempt
to pick his brain a bit. If anyone would know, he would.
I will say this much, however: Looking back over the past 20+ years
of nixie tube collecting and use, I am concluding that
Burroughs 6844A tubes are often found bad for a variety of reasons.
Have had many scrounged up at hamfests, etc. Lots of bad ones.
However, the National brand NL-6844A tubes seem to have a much better
chance of still being ok.
6844A turns out to be not such a great tube. But I built a clock that
has them prominently sticking out from the clear front
panel. I have another clock in the works that uses 8422 tubes.
Those seem to be quite good as far as a high percentage of them
still being ok. So my search for 6844A spares will continue. I am
now working with the Ebay seller of these (8) 6844A duds to
see if I can get back my $78 (ouch!) that I spent on them. -Chuck
---- Original Message ----
From: "Paul Andrews" <p...@nixies.us>
Sent: 12/11/2020 9:32:49 AM
To: "neonixie-l" <neonixie-l@googlegroups.com>
Subject: [neonixie-l] Re: Bad batch of Burroughs 6844A nixies
I have about 12 6844A, all NOS, none of them work - they show the same
symptoms that you described.
On Friday, December 11, 2020 at 1:45:30 AM UTC-5 gregebert
wrote:
I have not been able to figure that out for years. You would
think the internal leads were coated with an insulator so they dont glow, or
perhaps they use a different metal with a higher workfunction than the actual
cathodes, so they would not glow in normal circumstances. But when the cathodes
are still visible, I dont understand why they have no glow. I doubt they would
be selectively plated with another metal, which completely sputtered away,
leaving them unable to glow.
I have a bag of dead nixies, mostly 5031/6844, took 2
out, and microwaved them for 2 seconds. Got a brilliant crimson glow. One of
them shows some cathodes working, so now I have to go back thru the bag to make
sure I find the totally dead ones, or at least the ones that have glowing only
on the bondwires, and nuke them in the microwave oven. I have other boxes for
dying nixies, and so-so nixies, so I'm really surprised anything in the
"body-bag" of dead ones actually glowed. Unless perhaps the zap from the
microwave oven did something to the internal metal.
I have some more experimenting to do.
On Thursday, December 10, 2020 at 4:57:40 PM
UTC-8 Chuck wrote:
Burroughs 6844A is domed not flat. I
also have some National Electronics NL-6844A tubes. Frankly, I have had much
better
luck with the National Electronics
brand. This recently purchased batch of (8) Burroughs 6844A tubes is a bad
batch.
The boxes all are stamped MAR 4 1968.
The tubes themselves are date-coded 6750 F20. In white letters stenciled on
the glass:
"Burroughs 6844A NIXIE".
The test I did was that the anode got
connected to +170 volts DC through a 15k resistor. Then the digit cathodes
were selectively
grounded to the negative side of that
power supply. On all (8) of these Burroughs tubes, most of what is seen is
an intense glow concentrated
around the tiny internal wires which
connect the digit cathodes of the stack, to the pins. These tiny wires pass
closely to the outside of the
Anode casing which surrounds the digit
stack. The glow strikes in the wrong place. The glow is around the lead
wires instead of being
around the digits. I am very
confident from the way these tubes were in those boxes, that only one of the
batch had even ever been out of the box.
So I am curious what causes the glowing
lead wires.
Chuck
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