Portable
PLUS
Computer
Product History
11·9
11.4
Reference
Information
for Early C/D/E/F Versions
This section presents reference
information
for troubleshooting
and
repairing C
and
D versions
and
early E
and
F versions of the Portable PLUS. (The version is indicated by
the
model
number
printed
on
the
bottom
label
of
the
unit-refer
to table 1-1.) The E
and
F versions contain two piggyback PCAs
mounted
on
the memory PCA.
11.4.1
Removal and
Replacement
for Early ElF Versions
To
remove the piggyback PCAs from
the
memory PCA, first remove the two nuts
that
hold
each PCA,
then
use a screwdriver to carefully
pr
y
up
the edge
of
the PCA next to its connector.
Reassembly
Note:
Be
sure a spacer is installed
on
each
mounting
stud
before installing the
piggyback PCA. After installing the two nuts, place a drop of thread adhesive (part
number
0470-1306) on each nut. Finally, install a piece
of
tape (part
number
0460-2027) along
the
gap
between the piggyback
PCAs-it
should cover the connector
pads
on
both
PCAs.
11.4.2
Troubleshooting Early C/D/E/F Versions
Troubleshooting procedures for C
and
D versions
and
early E
and
F versions are identical to those
presented in chapter 8 with these exceptions (detailed information follows):
• Main Diagnostic Procedure.
When
you first
turn
on the computer, you must verify that the memory
PCA is configured properly by checking the
amount
of
available memory.
• Interpreting Diagnostic Test Results.
You
must
interpret the ROM failure codes to account for
the
presence
of
s
ix
ROM ICs that are soldered in place.
You
can't
perform component-level repair
on
the RAM ICs because they're surface-mounted.
• Repair Procedures. For
startup
problems, you must verify
the
configuration
of
the memory PCA.
For repairing the processors, the
ROM-select
IC
generates six select signals.
Main
Diagnostic Procedure.
When
you first
turn
on
the computer
and
the
main
PAM
screen appears,
you should check the
amount
of available memory
shown
at the upper-right corner
of
the
PAM
screen.
If
the
amount
is unreasonable considering
the
amount
of RAM in
the
computer, check the
configuration
of
the memory PCA as described
under
"Repair Procedures" below.
Interpreting
Diagnostic Test Results. Table 11-4 lists actions you
should
take for
the
indicated di-
agnostic test results.
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