Updated schematics are posted here:
http://www.Pinball-Mods.com/blogs/wp-content/uploads/2013/04/Bally7NixieFabB.pdf<http://www.pinball-mods.com/blogs/wp-content/uploads/2013/04/Bally7NixieFabB.pdf>
Fab B changes:
- Changes around D[5..7];
- 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.
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