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Model
1331A
8-30.
SEMICONDUCTOR REMOVAL AND REPLACE-
MENT.
8-31.
Figure
8-1
is
included to
h elp
identify the
leads
on the common
shapes and sizes
of semiconductor
devices.
When
removing a semiconductor, use long-
nosed
pliers as a
heat
sink
between
the
device
and
the
soldering iron
.
When replacing
a semiconductor,
ensure
sufficient
lead
length
to
dissipa
te
the
soldering
heat
by us
ing
the
same length of exposed
lead
as
used
for
the
original
part.
8-32.
CIRCUIT BOARDS.
8-33. The
following
paragraphs provide
information
regarding servicing procedures for
etched
circuit
boards.
8-34.
BOARD CONNECTIONS.
8-35.
Square-pin connectors are identified
on
cir-
cuit boards
by
the
color
code
of the
connecting
wire.
Connector pins
on
plugs
and jacks
are
identified by
either
a numera
l or
a letter. The
letters G,
I,
0
,
a
nd
Q
h
ave
been
omitted.
T
a ble 8-1
shows
the types
of
board connections
used in
the instrument.
8-36.
SERVICING ETCHED CIRCUIT
BOARDS.
8-37.
This
instrument
uses
etch
ed
circuit
boards
with plated-through
component
h
oles.
This allows
components to
be
removed or
replaced by
unsolder-
ing
from
either
side
of
the board. When removing
large
components, such
as potentiometers, rotate
the
soldering
iron
tip
from
lead
to
lead
while applying
pressure
to the part
to lift
it from
the board.
HP
Service Note
M-20E conta ins
additional information
on
repair of
etched
circuit
boards.
8-38.
HEAT
SINKS.
8-39.
The
h
eat
sinks used on this instrument are
a
ll
of
the friction type.
They can
be removed by
care-
fully pulling them
off.
When
rei nsta
lling,
support
the
hottom
of
the transistor before
pushing the
heat
sink
on. Transistor
damage
may
result if
the
transistor legs are
bent.
8-40.
TROUBLESHOOTING.
8-41. The
most
important prerequisite
for s
uccessful
troubleshooting is understanding
how the instrument
is
designed to
operate a
nd
correct
use
of
front
panel
controls.
Improper
control
settings or circuit
Service
connections can
cause apparent
malfunctions.
Read
Section
III
(Operation)
for an explanation of
controls
a
nd
connectors a
nd
general operating
considera
tions.
Read Section
IV
(Principles
of Operation) for ex-
planations
of
circuit theory.
8-42.
If
trouble
is
s
uspected,
visually inspect the
in-
strument.
Look for loose
or
burned
components
that
might
s uggest
a
source of
trouble.
Ch eck
to
see
tha
t
a
ll
circuit
board
connections
are making good contact
and are not s
horting
to an adjacent
circuit. If no
obvious trouble
is
found,
check the
power supply
voltages
in the
instrument.
Prior
to
any
extensive
troublesh
ooting,
a
lso check
th
e
external
power
sources.
8-43.
DC VOL TAG ES.
8-44.
On some of
the
schematics,
de
voltages are
indicated for active
components
(transistors, etc.)
Conditions
for
making these voltage measurements
are listed adjacent
to the
schematics.
Since the
con
-
ditions
for
ma
king
the
measurements may differ from
on circuit to
a nother,
a lways check
the specific
condition listed adjacent
to the
schematic.
8-45. WAVEFORMS.
8-46.
Waveform m
easurement points
(illustration
11
on
table
8-1) a re
placed
on
the
schematics
along
main signal paths.
The
numbers
inside
the
measure-
ment point
symbols
a re
keyed
to
waveforms
and
waveform
measurement conditions
adjacent to the
schematics.
Like the
de voltage
measurement
con
-
ditions,
wa veform
measurement conditions
vary
from one
circuit
to
a
nother.
8-47. TROUBLE
ISOLATION.
8-48.
The
power
s upplies
and
a
mplifiers in
Model
1331A
a re
conventional a
nd
respond
to conventional
troubleshooting techniques.
Schematics
1
through
6
a
nd
associated
illustrations
are
provided
as trouble-
s
hooting
guides.
8-49.
The
pulse circuits
on
schematic
7 react
differ-
ently
for
each
of
the
instrument's
modes and
func-
tions.
Schematic
7 is
reproduced
again in
figures
8-20, 8-21, and
8-22.
Figure
8-20 s hows
signal
paths,
de
voltages, and waveforms
for write mode.
Figure
8-21
is for
store
mode,
and figure 8-22
is for the
erase
function
.
The test
equipment
lis ted
in
Section
V
is s uitable for
troubleshooting the instrument.
8-3
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