Play Meter

ADDED CHIP
: ,Oi
DUAL
J · K Flip· Flo,
e
TO 09 , 6
J
K
o
0
CK
C
~
I
• ,
0
I
I
0
I
t
+
+
I
X
X
)(
0
= HI
to
~
LO
_ oJ
G-
STA'(
0
I
\
C.HA rH'I£. S STATE
0
ilUH-l 5 I S Tl o ,..l
X = IRRELeVANT
Figure 5
Figure 3
r
Finure 4 . ,
.:...;.7_
EXISTING
t
I
Hit1
I
J7,12
I
I
I
I
I
D9
played . 09 pin 6 changes state
every time a tank is hit .
L8 pin 13 is labeled start and
pulses LO each time a new game
starts . L8 pin 13 is tied to the
" clear" (C ) input of the J -K.
A ccording to the truth table
(Figure 5) , if " clear" is LO, 0 is
forced LO . So at the beginning of
each game, the playfield is the
same . Changing the wire . on the
74107 from pin 3 to pin 2 will cause
th e other playfield to be displayed at
th e beginning of each game .
,
..
COIN MACHINE
TRAINING FOR
REPAIR
MAINTENANCE
Trouble Shooting
I
L ___ ....1
START
L8, 13
I
8) Solder a jumper (e) from 74107
pin 3 to 09 pin 6.
9) Solder a jumper (f) from 74107
pin 13 to L8 pin 13 .
10) Check for shorted pins or
traces . Cut off the unused pins on
the 74107.
(This is optional.)
How It Works
Now , refer to Figure 4. J7 pin 12
is a signal that pulses HI each time
the white tank has been hit by the
black shell . J7 pin 2 is a signal that
pulses H I each time the black tank is
hit by the white shell . J7 pins 4,5,6
are an unused Nor gate . Pin 4 of J7
pulses LO if pins 5 or 6 pulse HI. So
if the white or black tank is hit by a
shell, J7 pin 4 pulses LO .
62
r
t
Figure 5 is the symbol and trut l1
table for the 74107 J - K fl ip-flop . In
our application, the J and K inputs
are tied H I. According to the truth
table, if J and K are HI , the output
(0) changes (LO to HI or HI to LO)
when clock (CK) goes from HI to
LO .
In Figure 4, J7 pin 4 is tied to the
clock input of the J -K flip-flop. So
the clock input of the J - K is being
pulsed LO each time the white or
black tank is hit by a shell . Each
time the clock goes LO , the output
(0) changes state .
Pin 3 (0) of the 74107 is tied to 09
pin 6 . If 09 pin 6 is HI , the normal
tank field is displayed . If 09 pin 6 is
LO, the alternate playfield is dis-
,
~
.. "
..
o
o
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o
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MUSIC and VENDING
~
"Your fut ure is our business.
II
Nevada Gaming
Schools, Inc.
3100 Sirius Road
Las Vegas. Nevada 89102
Tel: 702/ 873-2345
Certified BALLY trainong school
sixth year