Hi guys, I would like to contribute a few points to the discussion.
In contrast to the IN-13, the IN-9 does not have an auxiliary cathode to anker the glow discharge. This we all know. However it does have a zirconium bump/spike at the bottom of the main cathode which is otherwise made out of molybdenum. The combination of Neon/Zirconium gives a lower breakdown voltage than Neon/Molybdenum, everything else being the same. The purpose remains the same: the glow to start at the bottom of the tube. For the auxiliary cathode or zirconium spike methods to be effective, the voltage must be applied with a limited rate of increase. In other words, turn up the voltage slowly. This gives the physics in the IN-9 tube (have a read here http://www.saltechips.com/products/thermneon/theory.html) enough time to strike at the bottom of the tube before the applied voltage reaches the threshold where the rest of the cathode (molybdenum) strikes. This could be why Tim is finding the tubes to strike more reliably with half-wave rectified DC - the voltage rises slowly. I certainly don't think the tubes have developed the sort of nostalgia we have for neon, but for their original power supplies! :-) Assuming there is a glow going at the bottom of the tube, that still does not guarantee that the bargraph will not 'break' if a fast rise in current (i.e bar length) is allowed. By increasing the current the glow will try to cover more of the cathode surface. The glow at the bottom of the tube is providing ions locally, thus giving the glow a *preference *to continue growing from there if enough time is given (back to formative lag). If the current rises very quickly, distant positions on the cathode become 'disconnected' and will strike independently. At this point I must mention that argon-filled tubes have a shorter formative lag than purely neon tubes. This could be why Jon has had better luck with neon IN-9s. I experienced this first hand when working with the IN-13. Even if the aux cathode was active, the bargraph column would break when I wanted to 'instantly' move from the bottom to the top of the tube. The first measure taken was in hardware, by implementing an RC lowpass filter on the signal that controls the bargraph length. This slows down the signal to the tube's driver, and also forms part of a DAC. Have a look at the implementation on page 4 here http://www.saltechips.com/docs/thermneon-assembly-manual-v1.1-web.pdf The second measure was in software, the bargraph was incremented in thousands of small, fast steps, rather than in one big step. This eliminated the column breaking up issue. Regarding cleaning by cathodic sputtering, I found there was significant variation in a batch of 20 IN-13s. At the rated 5-ish mA, a few would light up up to the middle, a few all the way to the top and variations thereof. I was fortunate enough to come across and salvage a PS325 programmable HV power supply, so I used that to pulse the tubes at 100% overvoltage and overcurrent (280 V, 10mA) for 10ms every 1s. The current was limited to 10mA. I used a higher voltage to minimise the formative lag and a pulsing scheme to prevent overheating of the cathode. The current was chosen on a guestimate basis, the physics of cathodic sputtering are above my head. It took a minute or less for each tube. I am aware these tubes were heavily sputtered at the factory to give a high purity cathode surface - crucial for linearity. Briefly connecting two pieces of bare wire will work just as fine, but either put a current limiting resistor in series or wear goggles. Hope you find this useful. Alex. On Saturday, January 5, 2013 9:54:55 AM UTC, Alex wrote: > > Hi guys, > > I have been stock piling bar-graph tubes for a while now due to > their relatively cheap price and potential for interesting looking clocks > or other animated displays. > Due to a few being smashed in a recent shipment I decided to sit down and > work through testing all 450 or so IN-9's that I have to see what they are > like. > > Now, the first interesting point is that it seems that the white topped > IN-9 can be either Neon or Argon, it seems most of mine are Argon which is > quite annoying as the neon is a much richer red! I actually paid a bit more > for a couple of purple topped argon tubes assuming them to be a lovely > purple colour hence I was disappointed to find they are identical to about > 70% of my conventional IN-9's (and badly cathode poisoned)! > > This brings me to the second point and a quick question, has anyone got > any advice on getting these things to behave a bit better, some have fairly > epic cathode poisoning with the glow starting in the middle or snapping to > / hugging the other end or making large jumps up the tube. Are these things > usually quite awful or have I just got bad batches? I have tried burning > some in at upto about 40mA which has resolved some of the minor issues but > on some seems to make them even more keen to glow from the other end... > > I have a few hundred IN-13's to test as well soon and am just hoping they > are not as bad as these have turned out to be... > > Any advice on these tubes would be appreciated, hopefully a 64 channel VU > meter will follow before long ;-) > > - Alex > -- You received this message because you are subscribed to the Google Groups "neonixie-l" group. To unsubscribe from this group and stop receiving emails from it, send an email to [email protected]. To post to this group, send an email to [email protected]. To view this discussion on the web, visit https://groups.google.com/d/msg/neonixie-l/-/7DmGYlrYvHkJ. For more options, visit https://groups.google.com/groups/opt_out.
