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• Torque driver
If you have a torque driver, refer to the Torque column in the screw information table for each step.
– Make sure that you use the correct screw. It is recommended to use new screws for replacements. If
you have a torque screwdriver, tighten all screws rmly to the torque specied in the screw information
table for each step.
– Ensure torque screw drivers are calibrated correctly following country specications.
Retaining serial numbers
This section includes the following descriptions:
• “Restoring the serial number of the system unit” on page 64
• “Retaining the UUID” on page 65
• “Reading or writing the ECA information” on page 65
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. These numbers need to remain the same throughout
the life of the computer.
If you replace the system board, you must restore the 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 latest version of LENOVO ThinkPad Hardware Maintenance Diskette or Maintenance Key,
and then restart the computer.
2. From the main menu, select 1. Set system identication.
3. Turn off the computer, and then turn on the computer again.
4. When the ThinkPad logo is displayed, press Esc.
5. Select 2. Read S/N data from EEPROM and follow the instructions on the screen. The serial number of
each device in your computer is displayed; the serial number of the system unit is listed as follows:
• 20 Serial number
6. Write down that number.
Note: The serial number of the system unit is also written on the label attached to the bottom of the
computer.
After you have replaced the system board, restore the serial number by doing the following:
1. Install the latest version of LENOVO ThinkPad Hardware Maintenance Diskette or Maintenance Key,
and then restart the computer.
2. From the main menu, select 1. Set system identication.
3. Turn off the computer, and then turn on the computer again.
4. When the ThinkPad logo is displayed, press Esc.
5. Select 1. Add S/N data from EEPROM. Follow the instructions on the screen.
64 Hardware Maintenance Manual