Star Tech Journal

25
STAR*TECH JOURNAL/JANUARY 1984
GINO RONDINA
RALLY VIDEO CAR CIRCUIT OPERATION (PART 3)
By Duane Erby, Kiddie Rides USA, Davenport, IA
I have covered many of the major circuits thus far in my series of articles
regarding the Gino Rondina Rally Video Car game. I have discussed the
video summing circuits, timing and control, and some of the circuits that
generate special effects to the CRT monitor. Many of the circuits to be
covered in this article should expand our knowledge on these topics.
To be covered are two circuits that generate the car video to the video
output circuitry that was discussed in part 1 of this series. Also to be
discussed are clocking circuits that supply signals to some of the circuits
discussed in part 2. These clock circuits, in general, control the speed of the
track and surrounding obstacles during acceleration and deceleration. They
also interact with the circuits that generate the player's race car and the
obstacle cars. To prevent excessive jerkiness in the movements on the
screen, simple RC networks were employed to slow down the action.
Beginning at Figure A is a circuit that serves to generate an engine sound
( accelerate and decelerate) and also steer the player's car circuit of Figure B.
The accelerator pedal in the ride itself contains a microswitch that connects
to the ACC points in Figure A. When the switch is closed, the 4016 IC
( G 13) enable inputs are enabled and G 13 C and D outputs drive Q 1. The
output of QI is a voltage transition from lo to hi and is labeled VCA UDIO.
This signal goes to the audio section covered in part I. VCA UD IO is merely
a control voltage that instructs the 5 5 6 in the audio stage to produce the
accelerate or decelerate sound.
ICs E13, DI 1, Dl3, and G7 are used in conjunction with each other to
generate four signals labeled SPEED 1, SPEED2, SPEED 3, and SPEED4.
During an acceleration the 22uf capacitor in line with pin 9 ofE 13 begins to
charge. As it charges, the output E13 (pins 2, 1, 13, and 14) will each
undergo a lo to hi transition. This action gives the video effect of the road,
speed changes, etc. The Op-amp E 13 is known as an enable device. The
outputs are DC level and enable the clock pulses present on the input pins 9,
13, 2, and 4 ofIC DI 1 to pass in the form of speed (1, 2, 3, and 4).
The remaining ICs of Figure A generate two very important signals
known as QXC and QYC. Since these signals are outputted by flip flops we
also have their NOTs available for use by the circuit in Figure B. The
function of this circuit is to clear binary counters and individual flip flops at
such times determined by the wiper of the potentiometer. The counters are
located in Figure B. By changing the maximum count of these devices, we in
effect are changing the timing of the circuit as a whole and the net effect is
seen as lateral movement of the player's car on the CRT monitor. I will limit
my discussion of this circuit here and will go on to say that if you experience
difficulty in steering the player's car, the first thing to check is the -5-volt
zener supply located on the power supply board. Improper voltage here will
cause too rapid or too slow lateral movement of the player's car. Check for
the + 12 and -5 volts at the pot itself and be sure there is no. wiring problem
between the pot and the logic boards. If all checks out, the problem will more
than likely be a defective op-amp at location F8, F9, or D 10. As a last resort
a logic probe will be required to find a defective digital IC.
Looking at Figure C we see several circuits that combine several signals
and output other signals. The circuit around IC ClO generates the signals
CAR*BNS, O.K., and O.K. During the play mode if the player's car
contacts a bonus marker, the bonus marker will change from whatever bonus
score is indicated to the letters O.K. This indicates that the logic circuits
have recognized the fact that the player is due some bonus points and is
graphically letting the player know this fact. The result is displayed on the
CRT in the bonus row and is summed together with "miles" to equal total
score. Ahhh yes ... for those of you who haven't figured it out yet, the first
row of digits on the CRT is the miles row. The second row is bonus points.
The third row is the total row. Total= "miles" + bonus.
ICs D13, Bll and Cll in Figure C produce the signals labeled
MENDX and MENSX. These signals are directed to IC C9 ( see schematics
in part 2). These signals are used in conjunction with the timing signals directed
to PROM A 11 which contains the necessary logic to generate anything to be
displayed in the bonus box. If the player contacts a gas marker, the video is
changed from the letters "GAS" to a dripping oil can displayed graphically.
This is the only time the letters O.K. are not displayed on a bonus routine.
Continued on next page.
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