HP 3455A - Page 165

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^Ffor
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