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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 rmly to the torque specied in the screw information
table for each step.
• Ensure that the torque screw drivers are calibrated correctly following the country specications.
Retaining serial numbers
This section includes the following descriptions:
• “Restoring the serial number of the system unit” on page 54
• “Retaining the UUID” on page 55
• “Reading or writing the ECA information” on page 55
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 LENOVO ThinkPad Hardware Maintenance Diskette Version 1.76 or later, and restart the
computer.
2. From the main menu, select 1. Set System Identication.
3. Select 2. Read S/N data from EEPROM. The serial number of the system unit is listed as 20: Serial
number.
4. Write down that number.
Note: The serial number of the system unit also is 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 LENOVO ThinkPad Hardware Maintenance Diskette Version 1.76 or later and restart the
computer.
2. From the main menu, select 1. Set System Identication.
3. Select 1. Add S/N data from EEPROM. Follow the instructions on the screen.
If the MTM and Product ID numbers differ from each other on the rear label, use what is shown for the
Product ID eld. See example below:
MTM on rear label:
TTTT-CTO S/N SSSSSSS
54 Hardware Maintenance Manual