I told this story here to the previous generation of readers...
In a facility where I worked for a few years back in the mid-1970s there was
also a two-rack-cabinet trigger tube monster.
Its task was to check the teletype data that was arriving over an HF radio
network. When [parity] errors were detected the device issued a request for a
re-send.
The story goes that one Friday there was a fault and it was very intermittent.
The guy working on it was tearing his hair out and went home late that night.
It ran fine for the rest of the weekend.
Monday morning came and the equipment room staff tidied up and closed the
cabinet doors. Within hours the intermittent was back.
It took a while but eventually the penny dropped. The room was lit with strip
lighting [fluorescent tubes] banks that were seperately switched and also a
couple of PAR 38 flood lamps had been mounted on the ceiling pointing into
these cabinets because of the 'strange' construction and difficulty of working
on it. The room temperature did vary quite a lot too surprisingly. Desert
conditions outside with temp differentials of twenty-odd [degrees] C.
They eventually noticed that the fault wasn't present when the cabinets were
open and the bright lights were on.
The particular trigger tubes became hard to get and the particular guys working
on the equipment didn't manage to identify which tubes were the problem and
wanted to use the 'shotgun' approach with the fault. [Longer story there :-))
]
Eventually they took the doors off and made sure that the internals were
brightly illuminated!
John K
----- Original Message -----
From: Tomasz Kowalczyk
To: neonixie-l
Sent: Thursday, April 20, 2017 7:52 AM
Subject: Re: [neonixie-l] Constant current source design
W dniu wtorek, 18 kwietnia 2017 15:46:38 UTC+2 użytkownik jrehwin napisał:
- while testing it I found out that striking voltage of tubes is a max
value - I've tested one Z567M and one LC-631, they both strike with voltages
lower than their normal maintaing voltage!
Yes, it's a maximum value, so people can design circuits that are
guaranteed to strike even with a worst-case tube, under worst-case conditions
(see below).
I wonder if this low striking voltage is common among different tubes or
does the striking voltage change with temperature.
Temperature has a minimal effect on striking voltage. The big factor is
something to start the ionization cascade. If the tube is exposed to light,
photons will do the trick. Radiation of other forms will as well. Worst case
is in absolute darkness. For some designs, striking speed also matters: the
higher the voltage, the faster the tube will strike. For some designs this can
matter.
One workaround is to have a "primer" electrode, to provide a source of ions
to start the tube. While nixies don't normally come with primer electrodes,
you can use a decimal point as a primer, just hook it up via a very large
resistance. This will reduce the striking voltage and time significantly in
the dark.
- John
Wow. I didn't think much about how the ionization starts. I was quite
surprised as after reading this I turned off all lights in my room and with
150V the same LC-631 didn't start - but as soon as I put some light on it, it
indeed started glowing.
Unfortunately I can't use any decimal point as a ignition starter for the
simple reason - almost none of B13B socket tubes have a decimal point :) and I
own mostly those tubes (ZM1040, Z566M, LC-631, Z560M).
Thank you for sharing this information and making details of how nixies work
more clear to me. Also thank you for sharing the idea of programming the boost
converter to have a startup routine - this is so simple and yet I didn't think
about it.
Do you know if there is an effect of lowered striking voltage for some time
after the tube is turned off? I'm curious if it is possible to add PWM dimming
or even multiplexing with 145V power supply with 180V starting routine. As I
tested my LC-631 it seems to light up properly in darkness after it was lighted
once with my desk lamp - after that I can disconnect it, wait few seconds and
reconnect and it works immidiately. I don't know if it is a rule or just a
coincidence.
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