IBM ThinkPad 390E, Hardware Maintenance Manual

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The guide consists of a series of steps presented in a
checklist. Begin the checks with the power off, and the
power cord disconnected.
Checklist:
1. Check exterior covers for damage (loose, broken, or
sharp edges).
2. Power-off the computer. Disconnect the power cord.
3. Check the power cord for:
a. A third-wire ground connector in good condition.
Use a meter to measure third-wire ground conti-
nuity for 0.1 ohm or less between the external
ground pin and frame ground.
b. The power cord should be the appropriate type
as specified in the parts listings.
c. Insulation must not be frayed or worn.
4. Remove the cover.
5. Check for any obvious non-IBM alterations. Use
good judgment as to the safety of any non-IBM alter-
ations.
6. Check inside the unit for any obvious unsafe condi-
tions, such as metal filings, contamination, water or
other liquids, or signs of fire or smoke damage.
7. Check for worn, frayed, or pinched cables.
8. Check that the power-supply cover fasteners (screws
or rivets) have not been removed or tampered with.
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ThinkPad 390E