Hi Yall, I've attached a picture of the display pcb layout and a pdf of the schematic for it. The cathode drivers are just the MPSA42 with a 100K ohm base transistor and the collector is tied directly to the cathode and the emitter is tied to ground.
-joe On Mon, Feb 23, 2015 at 10:58 AM, gregebert <gregeb...@hotmail.com> wrote: > >> I will try the biasing. would biasing both sides help? This would be sort >> of like terminating the lines. >> > > No need to worry about termination at this frequency, as in reflected > waves, unless your PCB traces are several feet long... > I did check the datasheets for the MPSA42/MPSA92 and they are a good > choice because they have low leakage and high Vceo. > Therefore *driver* leakage is not your problem; can you post a schematic > of the driver & predriver circuits ? It could be the predriver. > > It's possible the device driving your PNP anode driver is leaky, causing > the PNP to turn-on slightly. Are you using a NPN predriver --> PNP driver > arrangement ? > If so, your NPN device could be leaking 0.1uA and your PNP will conduct > "beta" times this. This is easy to fix with a resistor across the PNP's > base/emitter to shunt-away > the predriver leakage. > > It's also possible there is noise entering the predriver; this is where a > scope will help. If you dont have a scope, then proceed with debugging he > predriver. > > -- > 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 email to neonixie-l@googlegroups.com. > To view this discussion on the web, visit > https://groups.google.com/d/msgid/neonixie-l/6c5852ba-b890-4d1d-b20f-0a4c2ab78324%40googlegroups.com > <https://groups.google.com/d/msgid/neonixie-l/6c5852ba-b890-4d1d-b20f-0a4c2ab78324%40googlegroups.com?utm_medium=email&utm_source=footer> > . > > For more options, visit https://groups.google.com/d/optout. > -- 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/CAE%2BVk6OWn90OEMi8ZxbfmNjM5TrfVRqhsF1A6D2%3DgeUcVeFHqA%40mail.gmail.com. For more options, visit https://groups.google.com/d/optout.
display_schem.pdf
Description: Adobe PDF document
