Page 124 - Theatre of Magic

White 0- Green
4 5 • 7
Dedlcallld Green- Green- Grwn- Grwn- flipper
Grounded Yellow Black Blue VIolet Grounded
Switch •• J207-4 J207-5 J207-6 J207-7 Switch ••
U20-15 U20-14 U20-13 U20-12
LOCK LEFT LOOP
1 SLING RIGHT
SWITCH MATRIX CIRCUIT
---------- --------- ---------------------------------- ------..,
, ,
, +12V '
j CPU BOARD I
Column(e,ample) 1---'"-:---0
,
,
,
,
,
, ,
... _-------_.-- --------_-- ------------------------------- -----_ ..•
Column
Off
On
Inoctive
Playfield Active
+5V +12V
J209
lN4148 White-XXX
lK
74LS240 I470pf Row
Off
On Row (example)
Switch Open
Switch Closed
The microprocessor is constantly strobing the column side of the switch. When point "A" on the column circuit toggles low, the
column side is active,
When a switch closes, the row side of the circuit activates. The "+" input to the LM339 drops below +5V causing its output to go
low, Corresponding row and column switches must be low at the same time for the switch to be considered closed by the
mlcropreceseor. When the switch opens, the "+" input to the LM339 is above +5V, its output is high and the row is inactive_
3-2