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Model 3455A
SERVICE
GROUP
F
Section VIII
b.
Replacement
Procedure.
1
.
Mount
the switch
body on
the
D/S
board and be
sure the
body
is
aligned with the other
switches
(NOTE:
very important as
the
switch
may
bind
if
it
is
not
straight).
2.
Using a
medium
temperature, broad,
tip
soldering iron or
woodburning
tool,
carefully
melt the
plastic
studs
down
into
a
little
dome
to
secure the switch
body.
3.
Insert
LED
with shorter
leg
toward top of
board.
Make
sure
LED
is
flush
with the board.
4.
Replace key
cap.
5.
Depress key
all
the
way
to seat
LED
in
place,
and
then solder
LED
using
a
minimum
of
solder.
6.
Hold
D/S
board
so
keys point
up and
reheat
LED
terminals to allow solder
to
flow
away
from
switch.
7.
Depress key
several
times
to
make
sure
key does
not
stick,
if
it
sticks,
repeat
(6).
8.
Remount
D/S
board
on
front
panel frame.
9.
Plug both connectors back
into
main
board.
10.
Remount
front
panel to
chassis.
1
1
.
Replace
ON/OFF
switch.
NOTE
Remember
to try
steps
(6)
and
(7)
of
"'Replace" before
replacing switch;
it
could save
time.
It
is
important
to
use
a low
or
medium
temperature
tip
soldering
iron,
as
exposure
to
SOO^F
for over
S
seconds could
damage
the
LED's.
8-F-B.
HP-IB Troubleshooting (Schematic
9).
8-D-9.
Before troubleshooting
the
HP-IB
section
of
the
3455A,
verify that
the
3455A
is
malfunction-
ing
and
make
sure the
"problem"
is
not
due
to externa]
programming
(see
Section
III
of
this
manual).
a.
If
incorrect
data
is
sent
over
the
HP-IB
lines,
make
sure the
data
is
different
than
what
is
displayed
on
the front panel.
If
the
data
is
the
same,
the instrument's
HP-IB
Section
is
not
at fault.
b.
Check
for a
bad
connection between
the instrument's
HP-IB
connector
(J3)
and
the
connector
of
the
HP-IB
cable.
Clean both
connectors,
if
necessary.
Use
a
good
freon
based
contact
cleaner.
Also,
make
sure
the
HP-IB
cable external
to
the instrument
is
good.
c.
Use
the
HP-IB
SA
Troubleshooting
Diagram
(Figure
8-H-27)
for
most of
the
HP-IB
Section
of
the
34SSA.
SA
can check most of
this
section,
except
for
the
HP-IB
lines
themselves.
Use
the
S9401A
Bus System Analyzer
for these
lines.
d.
Check
decoders
AIU19,
U20,
or
UIl.
8-75
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