Dell OptiPlex All-in-One Plus 7420 - System Board Removal and Installation

3. Install the back cover.
4. Install the stand.
5. Follow the procedure in After working inside your computer.
System board
Removing the system board
CAUTION: The information in this removal section is intended for authorized service technicians only.
Prerequisites
1. Follow the procedure in Before working inside your computer.
2. Remove the stand.
3. Remove the back cover.
4. Remove the memory.
5. Remove the graphics card.
6. Remove the system-board shield.
7. Remove the I/O cover.
8. Remove the bottom cover.
9. Remove the I/O bracket.
10. Remove the M.2 2230 solid-state drive in slot 0 or the M.2 2280 solid-state drive in slot 0, whichever is applicable.
11. Remove the M.2 2230 solid-state drive in slot 1 or the M.2 2280 solid-state drive in slot 1, whichever is applicable.
12. Remove the wireless card.
13. Remove the heat sink.
14. Remove the processor.
About this task
NOTE:
Replacing the system board removes any changes that you have made to the BIOS using the BIOS setup program.
Make the appropriate changes again after you replace the system board.
The following image indicates the connectors on your system-board.
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Removing and installing Field Replaceable Units (FRUs)