Bally 5000 Plus, Manual

Page: 373 / 388

11.
Appendices
Appendix
5: POWER SUPPLY
The
+
5V,
+
12V, and - 12V outputs are monitored by comparators
3
and 4 in the
LM339.
IF
these voltages fall below
+
4.5V, + 1O.BV, or - 1O.BV, respectively, then the comparators
generate an error signal at their respective outputs.
The error signals from comparators 1,
3,
and 4 are "or-ed" together into comparator 2.
When the output of comparator 2 goes to a high level, it provides base current to transistor
Q
1 which in turn generates the power fail signal for the game microprocessor. Components
R14 and , C2 comprise a time delay circuit which on power-up holds comparator 2 in the
power fail state for 400 milliseconds. This, in turn, holds the microprocessor inactive until
all supply voltages have stabilized to at least the minimum guaranteed operating voltage for
all circuitry.
11-11