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maintenance instructions.
IMPORTANT: As you remove each subassembly from the computer, place it (and all
accompanying screws) away from the work area to prevent damage.
Removal and Replacement Preliminaries 4-1
Cables and Connectors
Cables must be handled with extreme care to avoid damage. Apply only the tension
required to unseat or seat the cables during removal and insertion. Handle cables by the
connector whenever possible. In all cases, avoid bending, twisting, or tearing cables.
Ensure that cables are routed in such a way that they cannot be caught or snagged by
parts being removed or replaced. Handle flex cables with extreme care; they tear easily.
CAUTION: When servicing the computer, ensure that cables are placed in their
proper location during the reassembly process. Improper cable placement can
damage the computer.
4.3 Preventing Damage to Removable Drives
Removable drives are fragile components that must be handled with care. To prevent
damage to the computer or a removable drive, or loss of information, observe these
precautions:
Before removing or inserting a hard drive, shut down the computer. If you are
unsure whether the computer is off or in Hibernation, turn the computer on, then
shut it down.
Before removing a diskette drive, CD-ROM drive, SuperDisk LS-120 drive, or a
DVD-ROM drive, ensure that a diskette or disc is not in the drive. Ensure that the
drive tray is closed.
Before handling a drive, ensure that you are discharged of static electricity. While
handling a drive, avoid touching the connector.
Handle drives on surfaces that have at least one inch of shock-proof foam.
Avoid dropping drives from any height onto any surface.
Do not use excessive force when inserting a drive into a drive bay.
Avoid exposing a hard drive to products that have magnetic fields such as monitors
or speakers.
Avoid exposing a drive to temperature extremes or to liquids.
If a drive must be mailed, ship it in a suitable form of protective packaging.
Shipping the drive in standard packaging may not cushion it from destructive shock,
vibration, temperature, or humidity. Place a mailing label with the wording
Fragile: Handle With Care on the mailer.
After the hard drive has been removed from the computer, avoid turning the hard
drive and tray upside down. The drive is not secured to the tray and can fall out.
Do not place labels on the ventilation area on the hard drive.
Heed the labels on the hard drive.
4-2 Removal and Replacement Preliminaries
4.4 Preventing Electrostatic Damage
Many electronic components are sensitive to electrostatic discharge (ESD). Circuitry
design and structure determine the degree of sensitivity. Networks built into many
integrated circuits provide some protection, but in many cases the discharge contains
enough power to alter device parameters or melt silicon junctions.
A sudden discharge of static electricity from a finger or other conductor can destroy
static-sensitive devices or microcircuitry. Often the spark is neither felt nor heard, but
damage occurs. An electronic device exposed to electrostatic discharge may not be
affected at all and can work perfectly throughout a normal cycle. Or it may function
normally for a while, then degrade in the internal layers, reducing its life expectancy.
Packaging and Transporting Precautions
Use the following grounding precautions when packaging and transporting equipment:
To avoid hand contact, transport products in static-safe containers such as tubes,
bags, or boxes.
Protect all electrostatic-sensitive parts and assemblies with conductive or approved
containers or packaging.
Keep electrostatic-sensitive parts in their containers until they arrive at static-free
workstations.
Place items on a grounded surface before removing them from their container.
Always be properly grounded when touching a sensitive component or assembly.
Place reusable electrostatic-sensitive parts from assemblies in protective packaging
or non-conductive foam.
Use transporters and conveyers made of antistatic belts and roller bushings. Ensure
that mechanized equipment used for moving materials is wired to ground, and that
proper materials are selected to avoid static charging. When grounding is not
possible, use an ionizer to dissipate electric charges.
Removal and Replacement Preliminaries 4-3
Workstation Precautions
Use the following grounding precautions at workstations:
Cover the workstation with approved static-dissipative material (refer to Table 4-2
later in this chapter).
Use a wrist strap connected to a properly grounded work surface and use properly
grounded tools and equipment.
Use field service tools, such as cutters, screwdrivers, and vacuums that are
conductive.
When using fixtures that must directly contact dissipative surfaces, use fixtures
made of static-safe materials only.
Keep work area free of nonconductive materials such as ordinary plastic assembly
aids and Styrofoam.
Handle electrostatic-sensitive components, parts, and assemblies by the case or
PCM laminate. Handle them only at static-free workstations.
Avoid contact with pins, leads, or circuitry.
Turn off power and input signals before inserting or removing connectors or test
equipment.
4-4 Removal and Replacement Preliminaries
Grounding Equipment and Methods
Grounding equipment must include either a wrist strap or a foot strap at a grounded
workstation.
When seated, wear a wrist strap connected to a grounded system. Wrist straps are
flexible straps with a minimum of one megohm 10% resistance in the ground
cords. To provide proper ground, a strap must be worn snug against the skin. On
grounded mats with banana-plug connectors, connect a wrist strap with alligator
clips.
When standing, use foot straps and a grounded floor mat. Foot straps (heel, toe, or
boot straps) can be used at standing workstations and are compatible with most
types of shoes or boots. On conductive floors or dissipative floor mats, use foot
straps on both feet with a minimum of one-megohm resistance between the operator
and ground. To be effective, the conductive strips must be worn in contact with the
skin.
Other grounding equipment recommended for use in preventing electrostatic damage
include:
Antistatic tape
Antistatic smocks, aprons, or sleeve protectors
Conductive bins and other assembly or soldering aids
Non-conductive foam
Conductive tabletop workstations with ground cord of one-megohm resistance
Static-dissipative table or floor mats with hard tie to ground
Field service kits
Static awareness labels
Material-handling packages
Non-conductive plastic bags, tubes, or boxes
Metal tote boxes
Removal and Replacement Preliminaries 4-5
Electrostatic Voltage Levels and Protective Materials
Table 4-1 shows how humidity affects the electrostatic voltage levels generated by
different activities.
Table 4-1
Typical Electrostatic Voltage Levels
Relative Humidity
Event 10% 40% 55%
Walking across carpet 35,000 V 15,000 V 7,500 V
Walking across vinyl floor 12,000 V 5,000 V 3,000 V
Motions of bench worker 6,000 V 800 V 400 V
Removing DIPS from plastic tube 2,000 V 700 V 400 V
Removing DIPS from vinyl tray 11,500 V 4,000 V 2,000 V
Removing DIPS from Styrofoam 14,500 V 5,000 V 3,500 V
Removing bubble pack from PCB 26,500 V 20,000 V 7,000 V
Packing PCBs in foam-lined box 21,000 V 11,000 V 5,000 V
NOTE: 700 volts can degrade a product.
Table 4-2 lists the shielding protection provided by antistatic bags and floor mats.
Table 4-2
Static-Shielding Materials
Material Use Voltage Protection Level
Antistatic plastic Bags 1,500 V
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