Lenovo ThinkCentre M90n-1 Hardware Maintenance Manual page 88

Avoid contact with the hot computer. During operation, the computer becomes hot enough to burn the skin.
Before you touch the computer, turn off the computer, disconnect power, and wait approximately 30 minutes
for the computer to cool.
Replacement procedure
1. Remove the bottom cover. See "Bottom cover" on page 67.
2. Remove the M.2 solid-state drives. See "M.2 solid-state drives" on page 69.
3. Remove the Wi-Fi card. See "Wi-Fi card" on page 70.
4. Remove the wireless WAN card. See "Wireless WAN card" on page 71.
5. Remove the system board. See "System board and coin-cell battery" on page 74.
6. Remove the left cover. See "Left cover and front Wi-Fi antenna cable" on page 76.
7. Turn over the computer so that the bottom cover is facing down.
8. Remove the internal speaker.
9. Route the internal speaker cable through the hole used to hold the cable, and then install the internal
speaker.
10. Turn over the computer so that the bottom cover is facing up.
11. Reinstall all removed parts.
12. Reconnect the external cables and power adapter to the corresponding connectors on the computer,
and then reconnect the power cord to the electrical outlet.
Note: If a locking device is available, use it to lock the computer.
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M90n-1 Hardware Maintenance Manual