Handling Electrostatic Discharge-Sensitive Devices; Grounding Requirements - Lenovo ThinkCentre M79 Hardware Maintenance Manual

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 frame ground.
b. The power cord should be the appropriate type as specified in the parts listings.
c. Insulation must not be frayed or worn.
4. Remove the cover.
5. Check for any obvious alterations. Use good judgment as to the safety of any alterations.
6. 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.
7. Check for worn, frayed, or pinched cables.
8. Check that the power-supply cover fasteners (screws or rivets) have not been removed or tampered with.

Handling electrostatic discharge-sensitive devices

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 while handling the part.
• 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 the black side of 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 is desirable but not required to protect against ESD damage.
– Attach the ESD ground clip to any frame ground, ground braid, or green-wire ground.
– Use an ESD common ground or reference point when working on a double-insulated or
battery-operated system. You can use coax or connector-outside shells on these systems.
– Use the round ground-prong of the ac plug on ac-operated computers.

Grounding requirements

Electrical grounding of the computer is required for operator safety and correct system function. Proper
grounding of the electrical outlet can be verified by a certified electrician.
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ThinkCentre M79 Hardware Maintenance Manual