Doesn't sound like cathode-poisoning. Are you able to observe the straps welded to the individual pins ? Making a tube this size in a production environment is not trivial, so it's possible the weld broke, got dirty, etc.
You mentioned going up to 300V; that's plenty enough because the '1' is usually at the very bottom of the stack and works on both tubes. Theoretically, that should be the most difficult to illuminate as it's furthest from the anode mesh. '3' is on the top for my 5092 & 6091, and probably for your tubes. Most likely it's an open circuit. Do you have a capacitance meter ? You could try measuring capacitance between various cathodes to see if the dead digits have unusually low capacitance. That would bolster the broken connection theory. Come to think of it, I dont remember if I've ever tried measuring capacitance on my tubes so I'm not sure what kind of values to expect. Probably in the low pF range. -- 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/6c79cd1c-04f9-4eac-bbfb-2482883cb441%40googlegroups.com. For more options, visit https://groups.google.com/d/optout.
