Updated schematics are posted here:
http://www.Pinball-Mods.com/blogs/wp-content/uploads/2013/04/Bally7NixieFabB.pdfFab B changes:
- Changes around D[5..7] (solution for A5 & A6 digits not lite-ing):
- reworked for transistor inverters with pullups.
- U3A rewired to enable proper output with inverted signals.
- U3A always enabled ( !E tied to ground ).
- U4 I5 & I6 pull from Q1 & Q2 outputs instead of main connector so that cmos levels are observed at input of U4.
- D7’s resistor moved to base of Q20 and reduced resistance given below.
- D7’s non-emulated mode drives D2 which is now a SCHOTTKY diode so that lower Vf(D2) doesn’t impact ability to drive Q20 directly.
- Additional Boolean math notes around U3A decode logic.
- As observed in Nixie newgroup (among others); Added R70 and R71 to bases of Q6 and Q5 to help protect cmos logic in the event of a shorted MPS-A42.
- Reduced VR1 from 110V zener to 91V Zener to keep “standby” voltage rail lower than Nixie striking voltages.
- Changed R62 to 1% 30 ohm resistor to enable LED current measurement via ohms law.
- Added J5 to R62 to enable pads for LED current setpoint measurements.
- Collector / Anode resistors reduced from 22K to 2.2k to enable brighter digits in multiplex mode.
- Stuffed anode/kathode standby resistors. Was empty, is 300k.
- Changed TP4 testpoint. Was 80V is 90V.
Please let me know if you see anything of concern.
