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
v Electrical hazards, especially primary power (primary
voltage on the frame can cause serious or fatal
v Explosive hazards, such as a damaged CRT face or a
v 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.
1. Check exterior covers for damage (loose, broken, or
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
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.
Handling devices that are sensitive to
Any computer part containing transistors or integrated
circuits (ICs) should be considered sensitive to electrostatic
discharge (ESD.) ESD damage can occur when there is a
difference in charge between objects. Protect against ESD