I agree with Terry, you need to put some base resistors there. Your ubiquitous 9.1K will do. Of course, test whether the 4503 and the MPSA42s are still working. CMOS logic is not output short circuit proof, nor the MPSA42 can take too much base current. Additionally, the 9.1K base resistors will protect the 4503 in case of an open EB junction failure in the MPSA42. This due to the 4503 output parasitic diodes.
Gastón On Thursday, April 4, 2013 9:03:19 AM UTC-3, Terry S wrote: > > The 4503 is an tri-state device -- do you need pullups on the outputs? > I can't tell from a quick glance how you are using it. How about > series resistors to the bases of the transistors? I see those on A1 > thru A4. Without some series resistance your driver can only go to .7 > (Vbe) and I'm not sure how well it will like being clamped that low. > > > -- 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/msg/neonixie-l/-/PN_bi5dBXiAJ. For more options, visit https://groups.google.com/groups/opt_out.
