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6-10 REMOVING AND
REPLACING THE REAR
PANEL ASSEMBLY
This paragraph provides instructions for removing and replacing the
rear panel assembly of the 682XXB/683XXB. The rear panel assembly
contains the A21 Line Filter/Rectifier PCB, the A21-1 BNC/AUX I/O
Connector PCB, the line module assembly, and the fan assembly. Refer
to Figure 6-4 during this procedure.
Preliminary Disconnect the power cord from the unit and remove
the chassis covers as described in paragraph 6-2.
WARNING
When power is removed from the instrument, always allow
five minutes for the capacitors on the A21 Line Filter/Recti
-
fier PCB to discharge before removing the rear panel assem
-
bly.
Procedure Remove and replace the rear panel assembly as fol
-
lows:
Step 1 Using a Phillips screwdriver, remove the
screw on the top of the rear panel assem-
bly that fastens the rear panel assembly
to the bracket attached to the power sup-
ply housing.
Step 2 Turn the instrument upside down.
Step 3 Remove the three screws from the rear
panel assembly. (One screw fastens the
rear panel assembly to the bracket at
-
tached to the power supply housing; the
other two screws attach the rear panel as
-
sembly to the Motherboard.)
Step 4 Return the instrument to the upright po
-
sition.
Step 5 Remove the screws attaching the rear
panel assembly to the chassis sides.
Step 6 Using a
7
16
-inch wrench, disconnect the
coaxial cables (W110, W109, and W130)
going to the rear panel 10 MHz REF IN,
10 MHz REF OUT, and FM IN BNC con
-
nectors.
Step 7 Disconnect the coaxial cables W127,
W128, and W129 from the A21-1 PCB by
lifting up on the cable connectors.
Step 8 Remove the power supply cover and set it
aside.
682XXB/683XXB MM 6-13
REMOVAL AND REAR PANEL
REPLACEMENT PROCEDURES ASSEMBLY