Star Tech Journal

STAR* TECH Journal
October 1992
would appreciate it if you have
been following a logical service
procedure so that you do not have
to be walked through the prelimi-
naries. Procedure? Read on ...
One of the most important as-
pects of confirming the complaint
is being able to reproduce it.
Some problems are constant, oth-
ers come and go. Anything that
will consistently affect the prob-
lem is evidence that can be used
in isolating the bad parts. Some
examples:
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If the team is functioning prop-
erly, two things will occur. One,
• he will be told in specific terms
what the machine is, or is not
doing that needs to be taken care
of. Secondly, he will make sure
that information is relayed to
anyone he then sends the ma-
chine or board to. If those two
rules were followed the industry
would look a lot more intelligent
than it does.
~
•
The second aspect of the team is
that there is backup available for
whatever you may be doing. You
may be in over your head on a
machine you have never seen be-
fore in the darkest corner of the
dingiest bar in the smallest town
of your area, but there is someone
you can reach by phone who can
give you some pointers.
There are really only two qualifi-
~. cations here for getting good help.
The first is that you need to call
during regular business hours,
the other is that the one you call
:
The second as-
pect of the team
is that there is
backup ...
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Action related. An older Rockola
Juke with a circuit breaker blown
right at the end of the record
pointed to a reversing relay. Any
sequence of events that leads to
the problem is significant. Many
customers talk nonsense about
what they think is causing the
problem, but every once in a
while there is vital information
there ...
Stage two in our procedure is to
isolate the problem to a stage, a
board, or an assembly. This may
make the difference between
whether you have to remove and
possibly ship a board or a whole
game. On a video game there are
a few critical checks that will tell
a lot in a hurry.
Most crucial is the five volt sup-
ply. If that is missing or below,
say 4.5 volts the game hasn't got
a chance of coming up. lfit is over
six volts it is safe to expect major
damage to the logic boards. 12
volts, and -5 volts are associated
with audio on newer games.
A quick check for video output
from the logic board is with a
voltmeter. The RGB outputs will
measure something less than five
volts, but the important thing is
to look for change over a ten sec-
ond or so period. This is because
the average voltage on each color
will change as the scenes change
on the game. The same goes for a
missing color. Your meter cannot
read the video signal, but the
voltage average will tell you al-
most as much. Make sure it is in
attract mode for this test, as the
screen may not change with a
credit on it.
Always check the five volt level
on the board itself. Plugs are a
notoriously weak point in the sys-
tem. When in doubt, scope the
voltage for noise of hum. A bad
filter capacitor, such as the big
blue one in the older Atari's, can
leave enough 'holes' in the output
to keep the computer locked up
while still reading about 4.8v on
the meter. Likewise, other bad
caps or transistors can do the
same with noise.
Next month: Substitution and
Isolation techniques. The Team
Approch, Profitability and
more ...