Star Tech Journal

6
STAR*TECH JOURNAL/NOVEMBER 1983
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GINO RONDINA
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RALLY VIDEO CAR CIRCUIT OPERATION (PART 1)
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HOFFMAN CJ HOFFMAN
CARMEL·BY·THE·SEA CALIFORNIA 93921 ·0896
By Duane Erby, Kiddie Rides USA, Davenport, IA
The following is the first of a series of articles
analyzing the circuitry of the Rally Video Car
by Gino Rondina, distributed by Kiddie Rides,
USA. The analysis is intentionally written in
such a manner so as to be understood by the
novice video game technician. Within this
article we will discuss the power supply (Fig.
C), the Audio circuitry (Fig. A), and the Video
circuitry (Fig. B). Subsequent articles will
cover the logic theory of operation, and hope-
fully provide the reader with a thorough
understanding of how the various circuits merge
at the video output circuit to form the composite
video displayed on the screen. We utilize sul>-
circuit schematics to assist in eliminating paper
shuffling and wasted time studying large
composite schematics and thereby maximize
potential revenue time.
The troubleshooting technique that should
be employed is the video technician's world
famous " studying the picture for what is not
there or there and shouldn't be can eliminate
1001 headaches" technique. If this fails, a
logic probe to the pins ofM4, L3 and MB (Fig.
B) can often tell the story. These letter/number
combinations locate the individual component
on the PC boards. As on a city map, you will
find PC boards marked with letters along one
edge and numbers along the adjacent edge.
Easy, huh?
So much for the rambling on. The power
supply (Fig. C), as you can see, is quite basic.
It employs a triple secondary transformer that
produces a 9.8vac to the large full wave bridge
on the heat sink and then to the UA 78MG/
2N3055 regulator circuit for the TTL Vee
positive Svdc supply. Voltage labeled pos.
A.B.F. is not utilized. The remaining 2
secondaries produce 15 .5 vac. Each is rectified
by individual full wave bridges. One is regulated
by a 7 812 for + l 2vdc 1-amp source; the other
is zener regulated for neg. 5 .1 vdc source.
The Audio circuit (Fig. A) generates the
"crash" sound. PS pin 11 accepts the signal
called Car·BNS which causes a "Bip!" noise
when bonus points are scored. Engine sounds
such as accelerate/decelerate are accepted in
the formofVc Audio by NIA, a 556 wired as a
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Everyone loves Whac-A-Mole!
Manufactu re d in th e U .S. A.
Makers of am usement games si nce 1970
Continued on next page.
- ~ - 11.v
WHAC
A
MOLE
Customers love to play, and
you 'll love the way it pays.
Call us and let us
tell you more.
Bob's Space
Racers, Inc.
427 15th Street
Daytona Beach ,
Florida 32017
Telephone:
904-677-0761
one-shol Pin 5 of NIA has the " Rombo"
engine sound going to a 10k resistor, one of 5,
which is a resistive" adder'' circuit that combines
the various sounds. Audio Riserva is a " beep-
ing" sound that indicates a low fuel level.
Vicita Ex. play signals that a score of 400+
points has been reached and the driver should
look for curving road ahead This signal is a
constant audio tone. Audio output is achieved
by an NPN transistor buffer driving an NPN/
PNP complimentary output arrangement The
5837 chip is a white noise generator used
during a "crash". The "boom" sound is gener-
ated by IC-PS and the transistor it drives and
associated components when triggered by the
crash signal. Later on we will cover the origins
of these control signals.
The Video circuit (Fig. B) serves two basic
functions that are required by any color video
monitor. The first function is to take all video
signals and combine each, as required, to
produce the individual red, green, and blue
chroma signals. As shown, the output ofM3, a
74LS08 Quad 2 input AND gate, pin 11 is red
signal out to the red gun driver circuits in the
video monitor. Pin 6 outputs the green chroma
to green gun driver amplifiers of the~tor,
pin 8 to the blue amplifiers. The BLK are
blanking signals that impede chroma informa-
tion during retrace periods. IC PS is an inverter
(part of a 7416) that supplies horizontal and
vertical sync pulses to the vertical and hori-
zontal sync circuits in the monitor. The remainder
of the sync circuit will be covered later.
The logical function ofM4 (Quad 2-input
NAND) and L2 (8-input NAND) is to combine
the other logic signals; Bonus (bonus point
markers), CARI (red car video), fuel video
(red bar graph top left of screen), CAR4 (½ of
video information to produce yellow cars),
TRONCHI (tree trunks), and TRAIT (track
or white center lines). Pins 11 and 12 ( time
video, fuel video) are not used on our game
version. CHA on pin 5 of M4 is from the dot
matrix character generator circuit and produces
the scores located in the top right comer of the
FF SCR
CA.li?.·SNS
AUDIO
FIG. A