Philips pm2521 - Fault-Finding; General; Service Hints; Fault-Finding Procedure

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4.
FAULT-FINDING
4.1.
GENERAL
4.1.1.
Service hints
If servicing
is necessary
the following
points
should be
taken into
account in
order
to
avoid damaging
the
instrument.
—
Take care to
avoid
short-circuits
with
measuring clips
and hooks
if the
instrument is
switched-on,
especially
near the input
terminals
when
high-voltages are
present.
—
Use
a
miniature
soldering iron (35W
max.)
with
a
thin
cleaner or a
vacuum
soldering
iron.
—
Use
an acid-free
solder.
—
When
fault-finding,
remove top
and bottom
covers and
make sure that
the POWER
SUPPLY
is
connected
with
the main
board.
—
After repair,
the
instrument should be
recalibrated.
4.1.2.
Fault-finding procedure
This chapter
gives a fault-finding
procedure to locate
the faulty
section
in
the instrument.
From this
procedure the faulty
parts can
often be found by using
the
detailed flow
charts.
NOTE: The
procedure is only
intended as an aid to
fault-finding,
and
abviously that
the faulty
component
will not
be found in
every case.
Measuring
instruments
used:
—
Digital
multimeter.
—
Oscilloscope.
—
Counter.
4.1.3.
Fault-finding with
the signature
analyser
When the normal
fault-finding
does not
find the fault,
then it is possible to
use a
test-ROM.
The testrom
with several tests
for the
PM2521 is based
on signature
analysis. It
can trace
faults
at
component
level for
the controller
section,
display section
and even a part
of the analog
section.
The signature
analysis
fault-finding consists of a:
—
Testrom
with the
following tests:
—
Free
run tests
—
RAM and I/O test
-
Visual
L.C.D.
test
(noS.A.)
—
Switch
decoding test
—
Relay/FET
test
—
Static relay/FET test
(noS.A.)
—
Counter test
—
Interrupt
controller test
—
Test service
note
which includes:
—
Description
of how to
use the signature
analyser
—
Circuit
diagrams with
signatures
The
test— ROM
and
the service
note can be
ordered from
Concern
Service under
code nr. 5322
694
54013.