Turn an additional 180 degrees after the screw head touches the surface of the logic card:
180 degrees more
(Cross section)
vTorque driver
If you have a torque driver, refer to the ″Torque″ column with each step.
vMake sure you use the correct screw. If you have a torque screwdriver, tighten all screws firmly to the torque shown in the table. Never use a screw that you removed. Use a new one. Make sure the screws are tightened firmly
Retaining serial numbers
This section includes the following descriptions:
v″Restoring the serial number of the system unit″
v″Retaining the UUID″
Restoring the serial number of the system unit
When the computer was manufactured, the EEPROM on the system board was loaded with the serial numbers of the system and all major components. The numbers need to remain the same throughout the life of the computer.
If you replace the system board, you must restore serial number of the system unit to its original value.
Before replacing the system board, save the original serial number by doing the following:
1.Install the ThinkPad Hardware Maintenance Diskette Version 1.60, and restart the computer.
2.From the main menu, select 1. Set System
Identification.
3.Select 2. Read S/N data from EEPROM.
The serial number for each device is displayed. Write down the serial number of the system unit, designated as follows:
20:System unit serial number
Chapter 3. ThinkPad X20, X21, X22, X23, X24 55
