IBM ThinkPad T20, Hardware Maintenance Manual

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Safety inspection guide
The purpose of this inspection guide is to assist you in
identifying potentially unsafe conditions. As each machine
was designed and built, required safety items were
installed to protect users and service personnel from injury.
This guide addresses only those items. You should use
good judgment to identify potential safety hazards due to
attachment of non-IBM features or options not covered by
this inspection guide.
If any unsafe conditions are present, you must determine
how serious the apparent hazard could be and whether
you can continue without first correcting the problem.
Consider these conditions and the safety hazards they
present:
Ÿ
Electrical hazards, especially primary power (primary
voltage on the frame can cause serious or fatal
electrical shock)
Ÿ
Explosive hazards, such as a damaged CRT face or
a bulging capacitor
Ÿ
Mechanical hazards, such as loose or missing
hardware
To determine whether there are any potentially unsafe
conditions, use the following checklist at the beginning of
every service task. 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
continuity for 0.1 ohm or less between the
external ground pin and frame ground.
b. The power cord should be the type specified in
the parts list.
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
alterations.
6. Check inside the unit for any obvious unsafe
conditions, 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.
Introduction
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