2020 System Board Assembly - Lenovo ThinkPad L420 Hardware Maintenance Manual

2020 System board assembly

Important notices for handling the system board:
When handling the system board, bear the following in mind.
• The system board has an accelerometer, which can be broken by applying several thousands of G-forces.
Note: Dropping a system board from a height of as little as 6 inches so that it falls flat on a hard bench can subject
the accelerometer to as much as 6,000 G's of shock.
• Be careful not to drop the system board on a bench top that has a hard surface, such as metal, wood, or composite.
• If a system board is dropped, you must test it, using PC-Doctor for DOS, to make sure that the HDD Active
Protection System™ still functions.
Note: If the test shows that the HDD Active Protection System is not functioning, be sure to document the drop
in any reject report, and replace the system board.
• Avoid rough handling of any kind.
• At every point in the process, be sure not to drop or stack the system board.
• If you put a system board down, be sure to put it only on a padded surface such as an ESD mat or a corrugated
conductive surface.
After replacing the system board, run PC-Doctor for DOS to make sure that the HDD Active Protection System
still functions. The procedure is as follows:
1. Place the computer on a horizontal surface.
2. Run Diagnostics ➙ ThinkPad Devices ➙ HDD Active Protection Test.
Attention: Do not apply physical shock to the computer while the test is running.
For access, remove these FRUs in order:
• "1010 Battery pack" on page 57
• "1020 ExpressCard blank bezel and Media Card blank bezel" on page 58
• "1030 Optical drive or travel cover" on page 60
• "1040 Thermal cover" on page 61
• "1050 Hard disk drive or solid state drive assembly" on page 62
• "1060 DIMM" on page 64
• "1070 Fan assembly" on page 65
• "1080 CPU" on page 68
• "1090 SIM slot cover" on page 69
• "1110 Wireless WAN slot cover and PCI Express Mini Card for wireless WAN" on page 70
• "1110 mSATA solid state drive" on page 71
• "1120 Palm rest assembly with cables" on page 73
• "1130 PCI Express Mini Card for wireless LAN" on page 76
• "1140 Backup battery" on page 78
• "1150 Bluetooth daughter card " on page 78
• "1160 Media Card Reader slot board and Media Card Reader cable assembly" on page 79
• "1170 Keyboard" on page 81
• "1180 Keyboard bezel" on page 83
• "1190 LCD unit" on page 85
• "2010 Top shielding assembly" on page 88
Location of major sensitive components on the system board in ThinkPad L420, L421, and L520 models
The following components soldered on the top side of the system board are extremely sensitive. When you
service the system board, avoid any kind of rough handling.
a Accelerometer chip for the HDD Active Protection System
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Hardware Maintenance Manual