Atari STEEPLECHASE, Руководство по эксплуатации, техническому обслуживанию и ремонту

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,
This extremely low rate is slow enough to allow watching
events initiated by the pulser. Counter outputs, for example,
are more easily observed when the counter is pulsed or
clocked at this rate.
The logic pulser is also readily available from electronic
supply sources; a commercial model found satisfactory is
the Kurz-Kasch model H L 583.
(d) Oscilloscope. The most versatile test instrument, and
also the most expensive, is the oscilloscope. The high-speed
TTL integrated circuits used in video games produce fast­
rise-time signals. The oscilloscope should have a SO-MHz
bandwidth, dual trace and dual time base capability. These
latter features allow examination of both input and output
signals simultaneously, so that precise timing relation­
ships can be checked. The oscilloscope should also have
provision for internal or external sync.
Of the newer, solid-state oscilloscopes, a satisfactory
model is the Tektronix 465.
(e) VOM or Volt-Ohmmeter. This common measuring
instrument is extremely useful in video game trouble­
shooting. It can be used to check line voltage, transformer
secondary windings, continuity, resistance, power supply
voltages, and to some extent used for measurements in the
analog circuitry.
One commercial model found satisfactory is the Simp­
son 260.
6.2.2 OPTIONAL TEST EQUIPMENT:
(a) The Logic Comparator. This test instrument's main
benefit is that it can be used to check the functioning·of an
integrated circuit device while the device is still in place on
the printed circuit board. The logic comparator performs
the check by comparing the suspect ICs functioning with
that of an identical-type reference IC mounted in the in­
strument itself. Suppose that the functioning of a type-
74193 device on the PCB is suspected to be defective. First
insert a program card with a known-to-be-good 7 4193 into
the logic comparator, and then clip the comparator test
leads onto the leads of the suspect device. If there arc any
logic state differences between the reference IC and the sus­
pect IC under test, then an LED on the logic comparator
will light up to indicate which 0•1tput is not functioning
correctly. Once a defective IC .,as been located, it should
be replaced.
Logic comparators arc readily available from electronic
supply sources.
(b) Atari Universal Test Fixture. In situations where a
large number of video games arc being serviced, investment
in the Universal Test Fixture will be justified. This item of
test equipment forms a test station for troubleshooting
printed circuit boards after they have been removed from
the game cabinet. The Universal Test Fixture has a full set
of controls for operating the game and also has its own TV
monitor. The game's PCB is plugged into an edge connector
mounted on the side of the Fixture; with this arrangement
the PCB is positioned in a convenient way for connecting
probes and other test instruments.
A Program Card inserted into a receptacle in the top of
Fixture takes the place of the game's interconnect wires.
The program card thus sets up the Fixture for each particu­
lar game; the game's name is clearly printed on the program
card itself.
With the Universal Test Fixture the method of trouble­
shooting via substitution of known-to-be-good parts is made
fast and convenient. For example, suppose that the TV
picture in a game is completely broken up and you want to
determine whether the game or monitor is causing the
problem. Remove the PCB and plug it into the Fixture's
edge connector, and also insert the correct program card
for that game. If the picture on the Fixture's monitor is
correct, then you know that the problem lies in the game's
monitor.
6-3 SPECIFIC TROUBLESHOOTING
INFORMATION
The following subparagraphs give additional trouble­
shooting information about certain areas of the Steeplechase
game.
6.3.1 ANTENNA STATIC MODIFICATION: The antenna
is a wire inside the cabinet, approximately one foot long, with
one end connected to pin 12 of the PCB edge connector and
the other end intentionally left not connected. The antenna's
function is to prevent a player from getting free play sequences
by inducing a static electric charge in the coin entrance plate
or any other metal part of the game -provided that the wire
has been cut to optimum length.
On the printed circuit board, pin 12 of the edge connector
connects through adjustable potentiometer (Trimpot) R56 to
ground. The potentiometer's wiper arm connects to the base
of transistor Q4, which in turn can reset the credit latch. (The
operation of the credit latch is described in Section 3.4 of
Section Ill.) When a static discharge occurs, an electric current
is induced in this wire and an impulse is transmitted to the
credit latch circuit. This impulse resets the latch, turning off
game credit and switching the game over to the attract mode.
To test the static modification feature, touch the end of the
antenna wire with your finger. The human body usually has
enough capacitance to trigger the circuitry.
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