Agilent Technologies FieldFox N9923AN Service Manual page 109

RF Vector Network Analyzer
N9923AN
Replacing the A5 System Board
1. Separate the front and rear cases. See
2. Remove all measurement group assemblies as one unit. Refer to
Measurement Group Assemblies as One Unit" on page
3. Remove the I/O side panel. Refer to
on page 7-12.
4. Remove the A6 SOM board and flexible RF cables. Refer to
Board and Flexible RF Cables" on page
previous illustration. Note which cable is connected to which pc board connector to aid
in reinstallation.
5. Disconnect cable W3 from the A5 system board.
6. Remove four screws (item 4) from the system board shield and remove the shield.
Discard the screws, new ones are provided in the
7. Remove six screws (item 5) from the A5 system board, lift it up from the RF bottom
shield, and unplug it from the A4 RF board connector. Discard the screws, new ones are
provided in the Repair and Re-assembly
8. Remove the waffle gasket from the RF bottom shield and discard it. A new gasket is
provided in the Repair and Re-assembly
9. Manipulate the new waffle gasket by hand to eliminate curling and install it on the RF
bottom shield using the three dowel pins for alignment. It is not necessary that the
gasket be completely flat, just enough to remain in position while installing the new A5
system board.
10. Plug in the new A5 system board to the A4 RF board, over the new gasket, and aligned
with the three dowel pins in the RF bottom shield.
11. Position a new waffle gasket, from the
board top shield, on the A5 system board using the two dowel pins for alignment.
Manipulate this gasket by hand to flatten it if necessary.
12. Reinstall the system board top shield over the gasket and aligned with the dowel pins.
13. Hand-tighten four new screws (item 4) to secure the system board top shield and six
new screws (item 5) to secure the A5 system board to the RF bottom shield.
14. Torque these ten screws in the sequence shown by the circled numbers ( – ). Repeat
this torque sequence one additional time.
15. Reinstall the A6 SOM board and reinstall or reconnect all coax cables that were
removed or disconnected previously. Refer to
Flexible RF Cables" on page
16. Remove the system board to FPIB cable from the old A5 system board and install it on
the new board.
17. Reinstall the I/O side panel. Refer to
on page 7-12.
18. Perform the steps under
Service Guide N9923-90005
Removing and Replacing the Measurement Group Assemblies
"Separating the Front and Rear Cases" on page
"Replacing the I/O Side Panel, Doors, and Gasket"
7-29. Refer also to Enlarged Side View in the
Kit.
Kit.
Repair and Re-assembly
"Replacing the A6 SOM Board and
7-29.
"Replacing the I/O Side Panel, Doors, and Gasket"
"Post-replacement Procedure" on page
Repair and Replacement Procedures
"Removing All
7-25.
"Replacing the A6 SOM
Repair and Re-assembly
Kit, for the system
7-37.
7-8.
Kit.
7-31