Alright,
I did a little investigation. Hopefully, someone can point out the "oh god,
you're overdriving them" problem...
Investigation steps:
1. Scope HV line (HV supply is TES 1364 module)
2. Multimeter on 220Ω shunt resistor to get I_control
3. Input AC Signal -- steady 10kHz, varous levels
4. Input AC Modulation signal -- 10kHz AM'd 100% depth, 1Hz
5. DC Signal Input -- remove Microcontroller and input DC to 100kΩ resistor
LPF before the voltage follower.
Results:
1. HV Line, no input signal: Mean = 143V, V_pp = 8V
2. HV Line, full scale input signal (1.8V PP 10kHz sine wave -- to front
end): Mean = 143V, Vpp = 9V
3. Measure control current full system, suing AC signal input:
I_shunt, no signal = 1mA (micro is still here, did not scope micro, but
I suspect it was putting out a small nonzero PWM value)
I_shunt, full scale = 11.5mA
4. Measure control current, DC injection to IN-13 driver:
Vin (V) I_shunt (mA) Col Len. (cm)
--------- ------------------ ------------------
0 0.045 0.5
1 2.41 2.5
2 4.9 5
4 9.4 10
4.5 10.9 11
5 11.4 11
6 13.9 11
I also measured the current through the cathode resistor (220k in series
with the non-control cathode to ground):
Vin(V) I_cath (mA)
-------- ----------------
0 0.04
0.5 0.26
2 0.38
4.5 0.5
So what we see is that under normal operation, the tubes should never see
more than ~11mA, which is substantially higher than the expected max
current to get the full scale, and these tubes have seen a couple of hours
of burn in.
tubetester.com's translated datasheet
(http://www.tube-tester.com/sites/nixie/dat_arch/IN-13.pdf
-- scroll down) agrees with everyone here, that the max working current
*should* be ~5mA. I'll grant, my striking voltage is above the max. Taking
a closer look at voltages,
I see that the voltage between the anode and the indicating cathode when
the tube is at 0 scale is 111V. When I drive it to full scale, it rises to
139V. If I'm reading the aforementioned datashee correctly, the 0 scale
drop across the anode to indicating cathode should be at max 99V, so I'm
out of spec but not grossly so.
The only thing I can think to do is adjust the HVPS to be driving them at a
lower voltage (120V), but my recollection from when I breadboarded this is
that they do not strike reliably below about 140V.
Okay, so this has been a huge ramble, but if any of you have any insight
into this -- even if it only addresses a small part, it would be greatly
appreciated.
On Tuesday, January 24, 2017 at 11:58:31 AM UTC-8, TheJBW wrote:
>
> Sadly, both tubes got tossed with the trash before I even made this post,
> so no autopsy is possible. That said, I did inspect them visually. There
> was definitely no visible darkening of the tube, but I couldn't get a good
> look at the base of the cathode due to shielding. I would have noticed
> sputtering (which I looked for) after the first failure when a new tube was
> side by side with a tube destined to fail. The older tube was not
> noticeably dimmer than the new one.
>
> Signs indicate that erosion is the cause however, because of said "tink"
> -- The question is, could the sputtering have been confined to the area
> very near the cathode? Plus, it would make sense that the "low scale"
> portion of the cathode experienced much more erosion than the high scale,
> as the control portion of the system has an auto high voltage power off
> after 30 seconds but it would turn on when there were random transients
> (ground bounce, etc) during the day, and then go back to sleep. During that
> time, the tubes would be on for 30s with 0A control current. Perhaps that
> was bad for them.
>
> I'll run a test / video for everyone with controlled current over the
> weekend -- to demonstrate bar length at 0-15mA control currents.
>
> On Monday, January 23, 2017 at 1:57:18 PM UTC-8, Jon wrote:
>>
>>
>> Sounds like a good excuse for a tube autopsy...
>>
>> If you are indeed over-driving the current then you'll be sputtering
>> material off the cathode which after a while will have two effects. Firstly
>> there will be some gradual darkening of the tube as the material deposits
>> elsewhere. And secondly you'll see gross physical erosion of the cathode -
>> you can see a similar effect on dekatron cathodes where the glow has been
>> sitting stationary for a very long time (usually the zero cathode of the
>> tubes making up the higher order decades of a multi-tube counter). Given
>> that you describe a 'tink' noise, my guess is that the cathode has eroded
>> to the point where it physically broke, perhaps under the thermal stress of
>> being activated. Time for new tubes.
>>
>> The Soviet datasheets only promise 1000 hour life for IN-9 - I can't find
>> a similar overall guaranteed life specification for IN-13. My experience is
>> that they will last much longer than that if not overdriven.
>>
>> With regard to the current required to achieve full scale, yes there's
>> normally some cathode poisoning which needs to be burned off when you first
>> fire up the tubes (worse on IN-9 than IN-13), but then they should settle
>> down and operate at the specified sensitivity. The last centimetre or so of
>> the cathode is difficult to illuminate even in a well 'oiled' tube - they
>> lose linearity at the upper extreme. Best thing to do is not to worry about
>> trying to light up this bit.
>>
>> Cheers,
>>
>> Jon.
>>
>>
>
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