OK - I've looked at my NixiSat schematic, and although the 5530 symbol implies that Vdd is connected to +5V, it's actually connected to a rail called... VDD which in turn goes directly to the input jack via a 1N4741 11V Zener and a 100R resistor, i.e. if Vin from the wall wart is truly 12V (as it should be), then VDD should be 11V.
This is still driving the 5530s way out of spec, as the drive logic from the PIC is standard TTL with a 5V Vcc. Vih should be Vdd-2, i.e. 9V in this case, and it'll be nothing like that. For the PIC, Vol = 0.2V and Voh is Vcc-0.7, i.e. 4V3 and only half what the datasheet says the 5530 needs in this use case. One idea might be rotating the 5530s around and seeing if the problem moves with the driver... Whatever happens, there are no level shifters and it "just worked", so that was OK then :) Nick -- 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 neonixie-l+unsubscr...@googlegroups.com. To post to this group, send an email to neonixie-l@googlegroups.com. To view this discussion on the web, visit https://groups.google.com/d/msgid/neonixie-l/3c779b9c-c384-422a-a749-e58ca68db50e%40googlegroups.com. For more options, visit https://groups.google.com/d/optout.
