Retaining Serial Numbers; Restoring The Serial Number Of The System Unit - Lenovo ThinkPad Edge E420 Hardware Maintenance Manual

Notes:
• Make sure that you use the correct screw. If you have a torque screwdriver, tighten all screws firmly to the
torque shown in the table for each step in Chapter 8 "Removing and replacing a FRU" on page 55. Never
use a screw that you removed. Use a new one. Make sure that all of the screws are tightened firmly.
• 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 52
• "Retaining the UUID" on page 53
• "Reading or writing the ECA information" on page 53

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 Identification.
3. Select 2. Read S/N data from EEPROM.
The serial number of each device in your computer is displayed. The serial number of the system unit is
listed as 20: Serial number.
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 LENOVO ThinkPad Hardware Maintenance Diskette Version 1.76 or later and restart the
computer.
2. From the main menu, select 1. Set System Identification.
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 field. See example below:
MTM on the rear label:
52
Hardware Maintenance Manual