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SECTION
VI.
TROUBLESHOOTING
This section
of the
manual contains
troubleshooting hints, diagnostic
routines, and scope waveforms
for
both NTSC and PAL version
for the
Color Computer
3.
Scope settings are
noted on
the
individual waveform
diagrams
6.1
Introduction
The Color Computer
3
should
be
serviced only
by
qualified
technicians. Throughout
this
guide
a
basic knowledge
of
computers will
be
assumed,
as
well
as the
ability
to
use a
dual-trace oscilloscope. When
servicing any computer,
it is
important
to
distinguish
a
hardware
problem from
a
software problem.
Stated another way, just because
a
particular program does
not
yield
the
results desired by
the user, the
hardware
is
not
necessarily
at fault.
It
is,
therefore, recommended that
the
technician
be
thoroughly familiar
with
the
operation
of the
Color
Computer
3,
as
well
as
the
Theory
of
Operation. Diagnostic aids are
available from Radio Shack National
Parts
to
assist
the
technician
in the
servicing
of the
Color Computer
3.
Standard troubleshooting techniques
include these
steps:
identification,
localization, and isolation. The
first step, identification, consists
largely
of
making
sure that
a
problem
exists.
In
this
step
it
is
wise
to
check
the
obvious. Doing
so
can save
hours
of
troubleshooting
time only
to
find out that
a
cable was bad, or
that
it
was some other relatively
minor problem. After identifying
that
a
problem really does
exist,
localization
can
usually
be
accomplished
by
merely observing
the
symptoms. Isolating
a
problem down
to
the
defective component will often
involve
the
use of
test
equipment,
and sometimes, by part substitution.
Following
is a
list of
virtually
all
of the
problems
that
might
be
identified on
the
Color Computer
3:
6.2
Video
6.3
Keyboard
6.4
Processing problems
6.5
Cassette
6.6
RS-232C
6.7
Sound
6.8
Joystick
6.9
Cartridge problems
If a
problem exists
in
more
than one
area, the first course
of
action
should
be to look for
a
common
cause.
Although
it is
possible
to
have
two
or
more independent problems,
it is
more
likely that
a
single failure
can
cause
a
multitude
of
symptoms.
It
is
apparent,
for
example, that
all of
the
above areas will have problems
when
the
power supply
is
dead.
Once
a
problem has been identified
in
one of
the
above areas,
it
can
be
localized
by
observing
the
specific
symptom. For example,
if a
Cassette
problem
exists,
is it
a
Read problem,
a
Write
problem, or
a
Motor Control
problem? After
the
problem
is
localized, isolating
it to a
specific
component
is
usually not very
difficult.
-54-
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