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 electrical currents. Many customers have rubber
floor mats near their equipment that contain small conductive fibers to decrease electrostatic discharge.
• 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.
• 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 Field Replaceable Units (FRUs)
• Before you start to work on the computer, unplug the power cord. If you cannot unplug it, ask the
customer to power-off the electrical outlet that supplies power to the machine and to lock the electrical
outlet in the off position.
• If you need to work on a computer 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 a tester, set the controls correctly and use the approved probe leads and accessories for
– 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 the maintenance information. Use extreme care when measuring high voltages.
• Regularly inspect and maintain your electrical hand tools to ensure they are safe to use.
• Do not use worn or broken tools and testers.
• Never assume that power has been disconnected from a circuit. First, check that it has been powered off.
• Always look carefully for possible hazards in your work area. Examples of these hazards are wet floors,
non-grounded power extension cables, conditions that may cause or allow power surges, and missing
• Do not touch live electrical circuits with the reflective surface of a plastic dental mirror. This surface is
conductive, and touching a live circuit can cause personal injury and damage to the computer.
• Do not service the following parts with the power on when they are removed from their normal operating
positions in a computer:
– Power supply units
– Blowers and fans
– Motor generators
and similar units. (This practice ensures correct grounding of the units.)
• If an electrical accident occurs:
– Use caution; do not become a victim yourself.
IdeaCentre B340Hardware Maintenance Manual