Electrical Safety
Observe the following rules when working on electrical
equipment.
Important
Use only approved tools and test equipment. Some
hand tools have handles covered with a soft material
that does not insulate you when working with live elec-
trical currents.
Many customers have, near their equipment, rubber
floor mats that contain small conductive fibers to
decrease electrostatic discharges. Do not use this
type of mat to protect yourself from electrical shock.
Find the room emergency power-off (EPO) switch,
disconnecting switch, or electrical outlet. If an elec-
trical accident occurs, you can then operate the
switch or unplug the power cord quickly.
Do not work alone under hazardous conditions or
near equipment that has hazardous voltages.
Disconnect all power before:
– Performing a mechanical inspection
– Working near power supplies
– Removing or installing main units
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.
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.
Attention: 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.
Attention: 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 accesso-
ries 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.
12 ThinkPad 390/i Series 1700