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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 non-IBM alterations. Use good judgment as to the safety
of 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 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:
v Keep the parts in protective packages until they are inserted into the product.
v Avoid contact with other people.
v Wear a grounded wrist strap against your skin to eliminate static on your body.
v Prevent the part from touching your clothing. Most clothing is insulative and
retains a charge even when you are wearing a wrist strap.
v 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.
v 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.
250 Hardware Maintenance Manual