Lenovo 10YC, Hardware Maintenance Manual, Page: 9 / 106

After replacing a CRU, reinstall all protective covers, including the computer cover, before connecting
power and operating the computer. This action is important to help prevent unexpected electrical
shock and help ensure the containment of an unexpected fire that could happen under extremely rare
conditions.
CAUTION:
When replacing CRUs, be cautious of sharp edges or corners that might cause injury. If you suffer an
injury, seek medical care immediately.
Electrical safety
CAUTION:
Electrical current from power, telephone, and communication cables can be hazardous. To avoid
personal injury or equipment damage, disconnect the attached power cords, telecommunication
systems, networks, and modems before you open the computer covers, unless instructed otherwise
in the installation and configuration procedures.
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, 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 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 machine, unplug the power cord. If you cannot unplug it, power off the
wall box that supplies power to the machine and 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.
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
that tester.
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