Lenovo ThinkStation S20 4157 Hardware Manual page 154

10. Reconnect the heat sink fan cable. See "Locating parts on the system board"
11. Go to "Completing the FRU replacement" on page 131.
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Hardware Maintenance Manual
5. Carefully lift the heat sink off of the system board.
6. Remove the plastic cover from the bottom of the new heat sink to expose the
heat sink grease (this cover protects the heat sink grease from contamination).
Notes:
a. Do not remove the plastic cover until you are ready to install the heat sink
and fan assembly on the microprocessor. Do not touch the grease on the
heat sink and fan assembly. Do not put the heat sink and fan assembly
anywhere except on the microprocessor after the plastic cover has been
removed and the grease exposed.
b. Some heat sink part numbers will have orientation labels showing "Front
of System." Heat Sinks that do not have orientation labels should be
oriented so the fan cable is toward the board connector labeled "CPU Fan."
7. Place the new heat sink into position.
Important: Do not touch the thermal grease while handling the heat sink.
8. Align the four screws on the heat sink with the four mounting studs in the
chassis.
9. Follow this sequence to install the screws, noting that fully tight is 5 in-lbs +/-
0.5 in-lbs:
a. Partially tighten screw 1 , then fully tighten screw 2 , and fully tighten
screw 1 .
b. Partially tighten screw 3 , then fully tighten screw 4 , and fully tighten
screw 3 .
on page 137.