When all of the cathodes in a single tube lose large patches of coverage in a
short period of time, it still seems that it would be a failure of the gas
mixture. Over driving the cathodes for a period of time would cause an
eventual loss of brightness but it should cause variations among the cathodes
and not a sudden loss of coverage on all cathodes.
GregEbert suggested to look at the socket to make sure that pins aren't
stressed, which seems to match your description of how the tube failed...
Three failures in the same socket does seem to be more than coincidence and it
would be a good question to determine whether mechanical or electrical. You
should follow up with the group regarding future failures and/or findings as it
is interesting.
-------- Original message --------
From: Nicholas Stock <nickst...@gmail.com>
Date: 8/16/2016 8:26 PM (GMT-07:00)
To: neonixie-l@googlegroups.com
Subject: Re: [neonixie-l] One slot on my clock keeps burning out tubes, while
the others have been good for years. Thoughts?
Could the photocoupler at HC2 be the culprit at all? When you change the tubes,
is the brightness of the IN14 at that position the same as the rest?
On Tue, Aug 16, 2016 at 8:10 PM, gregebert <gregeb...@hotmail.com> wrote:
Since it's multiplexed, it might be worth comparing the 'on' time of each tube
(I'm guessing it's H2 on the schematic ?). You'll need a scope. Maybe there is
a quirk in the controller firmware that leaves this particular tube on longer
?? There's also a slight difference in the circuit around tubes H2, H3, and H4
though nothing pops out as a possible culprit.
Any chance there's a source of heat next to tube H2 ?
Only other thing I can think of is if the particular socket puts more stress on
this tube.
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