Basic HTML Version
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coil to the transistor tab. If the coil now pulls in, the wiring
between the transistor and coil is bad. Use an ohmmeter to
check for the break.
..
COIL STILL DOESN'T PULL IN. Wow, this problem's per-
sistentl If the coil still doesn't pull in, provide it with an alter-
nate source of 43 volts: Connect a jumper wire to the tab of
a
working
coil's power transistor. Touch the free end of the
jumper to the top of the inoperative coil.
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If the coil finally energizes, then you've identified open B
+
wiring, Trace the wiring with an ohmmeter. Locate and
repair the break. This procedure should restore normal
operation.
SWITCHES DON'T SCORE
INTRODUCTION
The switch matrix can seem very complicated, but really it's
fairly simple. Matrixed switches are arranged in rows and
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columns. When closed, each switch connects one row to
one column. Diodes prevent closed switches from creating
spurious circuits
("phantom
ll
switch closures).
The rows
and columns originate at a PIA
(Peripheral Interface Adap-
ter)
on the Control Board.
Typical Playfield Switch Circuit
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IN4148
RI2'j
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•.
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PLAYFIELD
SWITCH
WHT-jitEO
PLA'fFIELD 51
us
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4-22
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