148 Keysight FieldFox Handheld Analyzers Service Guide
Repair and Replacement Procedures
Removing and Replacing the Measurement Group Assemblies
7-
Replacing the A5 System Board
1. Separate the front and rear cases. See “Separating the Front and Rear
Cases” on page 115.
2. Remove all measurement group assemblies as one unit. Refer to
“Removing All Measurement Group Assemblies as One Unit” on page 136.
3. Remove the I/O side panel. Refer to “Replacing the I/O Side Panel, Doors,
and Gasket” on page 120.
4. Disconnect cable W3 and W4 from the A5 System board.
5. For N995xA and N996xA models, it is necessary to remove the top panel
assembly. Refer to “Removing and replacing the RF Top Panel Assembly”
on page 138.
6. Refer to Figure 7-27. Remove the RTC board. Refer to “Replacing the Real
Time Clock (RTC) Battery Located on the A5 System Board Shield” on page
144.
7. Remove the System board shield by removing the nineteen screws (2).
Discard the screws, new ones are provided in the Repair and Re-assembly
Kit.
8. Refer to Figure 7-28. Remove the four screws (2) that secure the A6 SOM
board (1) to the A5 System board. Discard these screws; new ones are
provided in the Repair and Re-assembly Kit.
9. Unplug the A6 SOM board from the A5 System board.
10.Refer to Figure 7-29. Remove the two screws (1) 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 Kit.
11.Refer to Figure 7-30. 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. Make sure the bullets are straight up when connecting the
System and RF boards.
12.Refer to Figure 7-28. Replace the SOM board onto the System board.
Install four new screws (2) from the Repair and Re-assembly Kit and
tighten them in the torque sequence indicated by the circled numbers (1 -
2 - 3 - 4) in the illustration.
13.Refer to Figure 7-31. Place the System shield onto the System board by
aligning the dowel pins. Replace the nineteen shield screws. Torque these
screws (plus the two System board screws, #13 and #21) in the sequence
shown by the circled numbers (1 - 21). Repeat this torque sequence one
additional time. Torque to 12 in-lbs.
14.Place the RTC board onto the System board shield and secure with the two
screws. Torque to 9 in-lbs.
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