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System board assembly and fan assembly - ThinkPad Edge E420

For access, remove these FRUs in order:

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 still functions (see below).

    Note: If the test shows that HDD Active Protection 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 conductive corrugated material.

After replacing the system board, run PC-Doctor for DOS to make sure that HDD Active Protection 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.

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] PCH (Platform Controller Hub)
[c] GPU (Graphic Processing Unit): Discrete graphics chip

Note: GPU ([d]) is only for the Discrete Graphics models. Integrated Graphics models do not have GPU on the system board.

For models with a discrete thermal module:


For models with an intergrated thermal module:



Step Screw (quantity) Color
1 M2 × 6 mm, wafer-head, nylon-coated (2) Black 0.181 Nm (1.85 kgfcm)


When installing: Make sure that the connector is attached firmly to the system board.



When installing:

  • Make sure that the cables are attached to the cable guides firmly.
  • Make sure that you route the cables correctly and you tape up the cables in the proper positions as shown in the following figure.


  • When you route the cables, make sure that they are not subjected to any tension. Tension could cause the cables to be damaged by the cable guides, or a wire to be broken.

Loosen the screws [2], but do not remove them.

Note: Different models might have different numbers of screws in step [2]



When installing: Before you attach the fan assembly to the computer, apply thermal grease, at an amount of 0.2 grams, on the part marked [a] as shown in the following figures. Either too much or too less application of grease can cause a thermal problem due to imperfect contact with a component. You need to peel the thin film off from the rubbers marked [b].

For models with a discrete fan assembly


For models with an intergrated fan assembly


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