<https://lh6.googleusercontent.com/-WtBxEUgqQjA/UzeVFdAZHPI/AAAAAAAAAHs/8MBYXpXChKU/s1600/original.jpg>
<https://lh6.googleusercontent.com/-VEHJNK7a-Lc/UzeVKvOwMhI/AAAAAAAAAH0/uEh_zcaOmiY/s1600/modified.jpg> I watched it today and saw it come from an hour behind to three hours ahead in the space of less than two actual hours, and I found the culprit - it's the 50 minute tube. It counts 58, 59, 00, 01, 02, and then somewhere in the middle of the ought-minutes the 50 tube strikes again. But, not every time. Tidak, I will try reducing the LED current further, since it's easy, but it's already down at 1mA. The efficiency of modern LEDs amazes me. I have sleeved the worst offending tubes, but only up to the top of the anode ring - maybe it needs more. People can see the tubes in action and I don't want the sleeves to be noticeable. Grahame, you are right, I did change the resistor values. For those following after, originally the cathode had a 27k resistor on top of a 56k resistor, with a 56k anode resistor. I changed all the 27k cathode resistors from 27k to 56k, and changed the anode resistor from 56k to 27k. See diagrams above - top is original, second is modified. What this did was increase the amplitude of the carry pulse from 21V, which was right on the margin, to 35V, without altering the tube current. All the stages that previously stuck then worked as intended, except in the dark. I'm not about to change it back to see if it now works with the original values, as that means changing more than 100 resistors and scrupulously cleaning the PCB afterward, since a little bit of contamination can cause it to stick. But I may increase the anode resistors since there are only a few and they're at the ends of the rows. What this will do is lower the pre-trigger bias applied to the next stage. It's nominally 56V at the moment, which was marginal with the 21V trigger pulse, but with the 35V pulse I can afford to drop it somewhat. At 43k the bias would be 52V. From the XC18 data sheet, the must-trigger voltage is 62 to 74 volts. Some tubes apparently don't make it. But with the 35V pulse, they would still get over 85V on the trigger. -- 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/msgid/neonixie-l/9514742b-110a-4eb4-b32f-ee7269d55a9d%40googlegroups.com. For more options, visit https://groups.google.com/d/optout.
