6-12 REMOVING AND
REPLACING THE
A21-1 PCB
This paragraph provides instructions for removing and replacing the
A21-1 BNC/AUX I/O Connector PCB, which is located on the rear
panel assembly (see Figure 6-4).
Preliminary Disconnect the power cord from the unit. Remove
the chassis covers as described in paragraph 6-2.
Remove the rear panel assembly as described in
paragraph 6-10.
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 A21-1 PCB.
Procedure Remove and replace the A21-1 PCB as follows:
Step 1 Using a Phillips screwdriver,remove the
four screws that fasten the A21 shield to
the A21 PCB.
Step 2 Remove the shield and set it aside.
Step 3 Disconnect the ribbon cable connector
from the A21-1 PCB.
Step 4 Using a ANRITSU P/N T1451 tool, remove
the dress nuts from the 12 rear panel
BNC connectors.
Step 5 Carefully remove the A21-1 PCB from the
rear panel assembly.
Step 6 Toreplace the PCB, reverse the removal
process.

682XXB/683XXB MM 6-17

REMOVAL AND

REPLACEMENT PROCEDURES A21-1 PCB