STAR*TECH Journal
... continued from previous page
or erratically, the game would
lock up. This led me to U24 the
input buffer, but replacing the
chip netted nothing. Different
start buttons proved unsuc-
cessful also.
THE FIX
Well, since the lock-up was
associated with the duration
the Start Button was held in
the "on" position, I ascertained
that the problem was linked to
the software loop that starts
the game and thus the actual
start-up of the game. So, if you
can't fix it, make it work. I
determined that if I could de-
vise a kluge (bastard circuit)
that would keep the Start But-
ton in it's "on" state until the
game successfully started,
without the customer thinking
the game was broken (because
when he touched the Start
Button, the game didn't start
"right now").
THE CIRCUIT
Since the problem seems to be
whether the Start Button is
held "on" when the software
addresses the input port (U24
input buffer), I devised a cir-
cuit to hold the Start Button
"on" for a duration of 1 second.
With a little experimentation,
1 second seemed the right du-
ration to keep the board from
locking up and not being too
long in duration for the cus-
tomer to think the game
wasn't going to start playing.
November 1993
the circuit is a 555 timer in
astable operation. A pull to
ground at pin 2 of the 555
timer, starts the astable
multivibrator. The duration of
the multivibrator is setup by
Rl and Cl (formula: 1/Rl * Cl
= 1/x). The output of the
multivibrator is pin 3 which is
fed into a NAND gate to pro-
vide correct logic to the game
board and buffering. C2 is for
stabilization of the 555 timer.
R2 is a pull-up resistor for con-
ditioning the input to the 555
timer.
PROCEDURE
I made my kluge with perf.
board that has traces on one
side. Using wire jumpers, I
connected the circuit shown in
Figure 1. I mounted the circuit
inside the cabinet at a conve-
nient location. Then attached
it to the JAMMA harness as
shown in Figure 2.
Jt.. 517\((r
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There will be a slight dela~
between selection of players (1
to 4 players), this is just notice-
able, but necessary-to accom-
plish our goal of No Lock-Ups.
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KLUGE
Refer to Figure 1 for the sche-
matic of the kluge. The heart of
figure 2
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