I measured at both points, the traces look the same. Anode resistors measure OK, as do the voltage divider and pull downs, etc.
Tubes are not socketed, and I have not tried adjusting the anode supply. I suspect the PNP base is open, although it measures the same as the other PNPs in the other two anode drivers. If the transistor is unable to turn on, I expected to never see 170 at the anode. But it is there. It looks like it decays at a faster rate than the other drivers. And I never see the voltage drop as one would expect when the tube ionizes, which I do see on the other drivers. Tells me no current is flowing, hence no lit digits of course. My scope is rather primitive, so not as helpful as it could be. The board is delicate, so I'm reserving my rework attempts for a well reasoned diagnosis and fix. Tonight I'll attempt to get some pictures of the scope waveforms. Terry On Friday, November 11, 2016 at 10:29:50 AM UTC-6, gregebert wrote: > > Are you measuring the anode signal at the anode-pin of the tube, or at the > driver ? Always possible something went awry on the board, etc (failed > anode resistor, tin-whisker shorting between traces). > > Is the anode supply adjustable ? Try boosting it a bit to see if the tubes > are aging and need more voltage to ionize. Seems unlikely, though, because > I would expect 1, not both, tubes on the driver to fail at the same time. > > Are the tubes socketed ? If so, number them, remove all of them, then use > a good tube to check each socket one-by-one. It will provide another clue. > > I was thinking that one or both of the tubes that doesn't illuminate has > an internal short; I've seen this with IN-1's though it was always > cathode-to-cathode, which resulted in 2 numerals turning-on at the same > time. > > If the tubes are soldered, I would try disconnecting the anodes of both > suspect tubes, then reconnecting them individually to see if one of them > has an internal short. > > -- 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/f142325e-8956-4a0a-b653-bf1cc570c70b%40googlegroups.com. For more options, visit https://groups.google.com/d/optout.
