in-9 bar length

[Thomas Kunzfeld]

hi guys,

I recently bought a bunch of different nixie tubes and as my very first project I designed a simple
thermometer with an in-9. at first the problem was that the bar was only about 3 cm long,
even at more than the highest rated current. I read somewhere that those tubes sometimes need
some sort of "burn in" phase, so i ran them at about 18 mA for half an hour. after that, the bar was
about 8 cm long. However, after not running for two days, the bar length dropped again by about
1 cm.

i use a switching power supply at about 130 V.

is there some way to get around this problem? or do I have to run them continuously...?

thanks!

[threeneurons]

Not to sound condescending, but did you check the polarity.

I find as I get older, I hook things up incorrectly, more often. In my youth (35 and under), I could wire-wrap a 30+ IC board. It would take 2 days to wire it up, and another day and a half, to do a continuity check against the schematic. Maybe, I'd make as many as 3 mistakes. I'd make that many mistakes today, on a circuit a tenth as complex ! 

[gregebert]

You may want to try IN-13 tubes; others have posted their successes with them on this site. I've yet to try them myself.

I had a bad experience with IN-9 tubes several years ago, and gave-up on them because the ones I have showed erratic and unrepeatable behavior. I've also had bad experiences with IN-1 nixies, but that's a different rant.

[Alex]

Use un-smoothed half or full wave rectified power, the repeated re-ignition seems to help on these.

- Alex

[Thomas Kunzfeld]

i checked the polarity multiple times, but just for trying I switched it around,
but then the tube would not ignite at all. so I am quite sure it is correct.

[Thomas Kunzfeld]

I heard that the in-13 would be better, but the in-9 were the cheapest... now I know why.
I would like to hear your rant about in-1 tubes, because I also bought a bunch
of these and wanted to use them in my next project...

[Thomas Kunzfeld]

i tried using a mosfet after the current sink which was driven by a
square wave. this should have the same effect of re-igniting the tubes, right?
however, this did not really help, I even tried a lot of different frequencies (from 10 hz to 500 hz)

[threeneurons]

Both the IN-13 and IN-9, have sustain voltages ~100V. The IN-13 is fullscale at ~4.5mA, and the IN-9 at ~10mA. If you're using a 130V supply, then just hook up the most basic circuit. The supply, a limiting resistor, and the IN-9 tube. Calculate the resistor for 10mA, with 30V (the difference of supply from tube). That would be 3K. Use the closest resistor you have. 3 1K in series, would be good. Then see what you have. With htis set up, measure the voltage out of the supply, then tube  drop, then the resistor drop. Do this all with it running, and not dissembled , while taking all three measurements.

I personally do not like using current meters while doing these kinds of measurements. The current will be the voltage drop of the resistor(s) divided by the resistance. Actually, I don't like using current meters at all. If I have to take a direct current measurement, I like using a current clamp.

[threeneurons]

My prior post is intended to isolate the problem. The tubes, themselves, maybe defective. Follow the rule of KISS (Keep It Simple Stupid). If you try to test them, in a complex circuit, you can't determine what is at fault. Too many variables. Divide-and-conquer. That's why you need just the tube, one resistor, and the power supply. See what you get, before proceeding. At least we can establish if the tubes are good, or not. As it stands, we don't know if the tubes are bad, or the circuit is not functioning as intended, or another component is defective. With a simple circuit, we eliminate as many variables as possible.

[gregebert]

Any thoughts about using a true DC supply (ie, filtered) versus half or full-wave rectified AC ? I seem to recall trying full-wave with and without a filtering cap, and both resulted in similar erratic behavior with my IN-9's.

[Dekatron42]

Looking through Russian literature I can only find circuits which use the IN-9 in half-wave rectified designs for checking the mains voltage, I haven't found any circuit with any control of the signal in any other way, you can see such voltage control pens on this site: http://www.petrofflab.ru/p/blog-page_12.html but you'll have to scroll down a bit but don't skip the rest as there are many nice photos there!

The IN-13 however is always shown in circuits with some type of control with transistors or other simple designs.

So I think that the IN-9 was mainly designed for simple designs with half-wave rectified voltages in mind and the IN-13 was designed with control in mind. There is even a photo of a VU-meter with IN-13 in an old Russian book. There can of course be other circuits but these designs repeat themselves across books from different writers.

/Martin