Screw Notices; Retaining Serial Numbers - Lenovo ThinkPad L390 Hardware Maintenance Manual

Screw notices

Loose screws can cause a reliability problem. In the ThinkPad notebook computer, this problem is
addressed with special nylon-coated screws that have the following characteristics:
• They maintain tight connections.
• They do not easily come loose, even with shock or vibration.
• They are harder to tighten.
Do the following when you service the computer:
• Keep the screw kit in your tool bag. For the part number of the screw kit, go to:
https://support.lenovo.com/partslookup
• It is recommended to use new screws.
• It is recommended to use each screw only once.
Tighten screws as follows:
• Plastic to plastic
Turn an additional angle of 90 degrees after the screw head touches the surface of the plastic part.
• Logic card to plastic
Turn an additional angle of 180 degrees after the screw head touches the surface of the logic card.
Notes:
• Ensure that you use the correct screw. It is recommended to use new screws for replacements. If you
have a torque screwdriver, tighten all screws firmly to the torque specified in the screw information table
for each step.
• Ensure torque screwdrivers are calibrated correctly following country specifications.

Retaining serial numbers

This topic provides instructions on the following:
• "Restoring the serial number of the system unit" on page 63
• "Retaining the UUID" on page 63
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L390, L390 Yoga, S2 4th Gen, and S2 Yoga 4th Gen Hardware Maintenance Manual