IBM 2179 Hardware Maintenance Manual page 111

Observe the following rules when working on electrical equipment.
v Find the room emergency power-off (EPO) switch, disconnecting switch, or
electrical outlet. If an electrical accident occurs, you can then operate the switch
or unplug the power cord quickly.
v Do not work alone under hazardous conditions or near equipment that has
hazardous voltages.
v Disconnect all power before:
– Performing a mechanical inspection
– Working near power supplies
– Removing or installing main units
v Before you start to work on the machine, unplug the power cord. If you cannot
unplug it, ask the customer to power-off the wall box that supplies power to the
machine and to lock the wall box in the off position.
v If you need to work on a machine that has exposed electrical circuits, observe the
following precautions:
– Ensure that another person, familiar with the power-off controls, is near you.
Remember:Another person must be there to switch off the power, if
necessary.
– Use only one hand when working with powered-on electrical equipment;
keep the other hand in your pocket or behind your back.
Remember:There must be a complete circuit to cause electrical shock. By
observing the above rule, you may prevent a current from passing through
your body.
– When using testers, set the controls correctly and use the approved probe
leads and accessories for that tester.
– Stand on suitable rubber mats (obtained locally, if necessary) to insulate you
from grounds such as metal floor strips and machine frames.
Observe the special safety precautions when you work with very high voltages;
these instructions are in the safety sections of maintenance information. Use
extreme care when measuring high voltages.
v Regularly inspect and maintain your electrical hand tools for safe operational
condition.
v Do not use worn or broken tools and testers.
v Never assume that power has been disconnected from a circuit. First, check that it
has been powered-off.
v Always look carefully for possible hazards in your work area. Examples of these
hazards are moist floors, nongrounded power extension cables, power surges,
and missing safety grounds.
v Do not touch live electrical circuits with the reflective surface of a plastic dental
mirror. The surface is conductive; such touching can cause personal injury and
machine damage.
v Do not service the following parts (or similar units) with the power on when they
are removed from their normal operating places in a machine. This practice
ensures correct grounding of the units.)
– Power supply units
– Pumps
– Blowers and fans
– Motor generators
v If an electrical accident occurs:
– Use caution; do not become a victim yourself.
– Switch off power.
– Send another person to get medical aid.
Chapter 8. Related service information
103