Lenovo T420 - Manual (Page 114)

1210 System board and ExpressCard slot assembly
For access, remove these FRUs in order:
•
“1010 Battery pack” on page 63
• “1020 ExpressCard blank bezel” on page 64
• “1030 Serial Ultrabay Enhanced device or travel bezel” on page 65
• “1040 Hard disk drive (HDD) and solid state drive (SSD)” on page 66
• “1050 DIMM slot cover” on page 69
• “1070 PCI Express Mini Card for wireless WAN” on page 71
• “1080 Keyboard” on page 73
• “1110 PCI Express Mini Card for wireless LAN” on page 81
• “1120 Keyboard bezel assembly, FPC cable, and Bluethooth daughter card” on page 83
• “1150 Speaker assembly” on page 91
• “1160 LCD unit” on page 93
• “1170 Fan assembly” on page 97
• “1180 CPU” on page 101
• “1190 Base cover assembly and DC-in connector cable” on page 102
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 HDD Active Protection System is not functioning, be sure to document the drop in a
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 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.
Removal steps of system board and ExpressCard slot assembly
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 CPU
b Accelerometer chip for the HDD Active Protection System
108 ThinkPad T420 and T420i Hardware Maintenance Manual