IBM 2254 Hardware Maintenance Manual

Also see for 2254: Hardware Maintenance Manual User guide

Contents

204 IBM : Hardware Maintenance Manual3. Check the power cord for:a. A third-wire ground connector in good condition. Use a meter to measurethird-wire ground continuity for 0.1 ohm or less between the external groundpin and frame ground.b. The power cord should be the appropriate type as specified in the partslistings.c. Insulation must not be frayed or worn.4. Remove the cover.5. Check for any obvious non-IBM alterations. Use good judgment as to the safetyof any non-IBM 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 beenremoved or tampered with.Handling electrostatic discharge-sensitive devicesAny computer part containing transistors or integrated circuits (ICs) should beconsidered sensitive to electrostatic discharge (ESD). ESD damage can occur whenthere is a difference in charge between objects. Protect against ESD damage byequalizing the charge so that the machine, the part, the work mat, and the personhandling the part are all at the same charge.Notes:1. Use product-specific ESD procedures when they exceed the requirements notedhere.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 andretains 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 thatmeets the specific service requirement.Note: The use of a grounding system is desirable but not required to protectagainst ESD damage.— Attach the ESD ground clip to any frame ground, ground braid, or green-wireground.— Use an ESD common ground or reference point when working on a double-insulated or battery-operated system. You can use coax or connector-outsideshells on these systems.— Use the round ground-prong of the ac plug on ac-operated computers.