Portable PLUS Computer
Troubleshooting
8·3
The following list summarizes the tests that
you
can use:
• Built.in diagnostic tests. Tests that are included in
and
executed from internal ROM.
You
use
a
menu
(figure 8-2) to select tests. These tests clear the Electronic disc
(Edisc)-be
sure
to
back
lip
all
files
onto
a
disc
before
running
these
tests,
then
reformat
the
Edi
sc
and
reload
the
files
after
the
diagnostic
tests
are
complete.
• Disc.based diagnostic tests. Tests that are included on the service disc, loaded into internal RAM,
and
executed from
RAM.
You
use a
menu
(figure 8-3) to select tests of each portion
of
the com-
puter. (One of the routines
burns
new
configuration EPROMs if the diagnostic module is
plugged
in.)
• Diagnostic module oscilloscope routines. Routines that are included in
and
executed from
EPROM in the diagnostic module. They establish conditions for using
an
oscilloscope to check
the
circuits.
A summary of each diagnostic test is included in chapter 10, "Reference
Information:
Test results will be printed automatically
if
an
HP-IL "ThinkJet' printer (HP 2225B) is connected to the
computer.
For assembly-level repair, the diagnostic tests indicate a bad assembly.
For component-level repair, the diagnostic tests indicate a bad component.
You
can use the oscillo-
scope routines to isolate
and
verify faults.
After
repairing
a
unit,
verify that
it
is
good
by
performing
a
complete
system
test
.
Tools
and
equipment needed for checking
and
repairing the computer are listed in table 1-3. (Refer-
ence information about special service equipment is in section 10.5.)
8.2
Troubleshooting
Procedures
This section describes how to use the diagnostic tests
and
procedures to locate
and
repair a problem.
Begin troubleshooting at the main diagnostic procedure in section B.2.1 below.
CAUTION
Be
sure to wear a grounded wrist strap and work at a bench that
is
electrostatically protected.
Many electronic components,
especially
the
display
module,
are highly susceptible to damage
by
electrostatic discharge.
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