Keysight N9912A Service Manual page 122

Repair and Replacement Procedures
Removing and Replacing the Measurement Group Assemblies
Replacing the A5 System Board
1. Separate the front and rear cases. See
Cases" on page
2. Remove all measurement group assemblies as one unit. Refer to
"Removing All Measurement Group Assemblies as One Unit" on
page
3. Remove the I/O side panel. Refer to
and Gasket" on page
4. Remove the A6 SOM board and flexible RF cables. Refer to
A6 SOM Board and Flexible RF Cables" on page
Enlarged Side View in 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
Re-assembly
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
8. Remove the waffle gasket from the RF bottom shield and discard it. A new
gasket is provided in the
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
system 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
➊➐➓
(
15.Reinstall the A6 SOM board and reinstall or reconnect all coax cables that
were removed or disconnected previously. Refer to
SOM Board and Flexible RF Cables" on page
7-36
7-9.
7-29.
7-14.
Kit.
Repair and Re-assembly
). Repeat this torque sequence one additional time.
"Separating the Front and Rear
"Replacing the I/O Side Panel, Doors,
7-33. Refer also to
Repair and
Repair and Re-assembly
Kit.
Repair and Re-assembly
"Replacing the A6
7-33.
Keysight N9912A Service Guide
"Replacing the
Kit.
Kit, for the