Lenovo N20 Chromebook Hardware Maintenance Manual - Lenovo N20 Chromebook - Page 9

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. Checklist: 1. Check exterior covers for damage (loose, broken, or sharp edges). 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 the frame ground. b. The power cord should be the authorized type specified for your computer. Go to: http://www.lenovo.com/serviceparts-lookup c. Insulation must not be frayed or worn. 4. Check for cracked or bulging batteries. 5. Remove the cover. 6. Check for any obvious non-Lenovo alterations. Use good judgment as to the safety of any non-Lenovo alterations. 7. 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. 8. Check for worn, frayed, or pinched cables. 9. Check that the power-supply cover fasteners (screws or rivets) have not been removed or tampered with. Handling devices that are sensitive to electrostatic discharge 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 damage by equalizing the charge so that the machine, the part, the work mat, and the person handling the part are all at the same charge. Notes: 1. Use product-specific ESD procedures when they exceed the requirements noted here. 2. Make sure that the ESD protective devices you use have been certified (ISO 9000) as fully effective. When handling ESD-sensitive parts: • Keep the parts in protective packages until they are inserted into the product. • Avoid contact with other people. • Wear a grounded wrist strap against your skin to eliminate static on your body. • Prevent the part from touching your clothing. Most clothing is insulative and retains a charge even when you are wearing a wrist strap. • Use a grounded work mat to provide a static-free work surface. The mat is especially useful when handling ESD-sensitive devices. • Select a grounding system, such as those listed below, to provide protection that meets the specific service requirement. Note: The use of a grounding system to guard against ESD damage is desirable but not necessary. - Attach the ESD ground clip to any frame ground, ground braid, or green-wire ground. - When working on a double-insulated or battery-operated system, use an ESD common ground or reference point. You can use coax or connector-outside shells on these systems. - Use the round ground prong of the ac plug on ac-operated computers. Chapter 1. Safety information 3