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Removal and Replacement
This chapter
provides general service information for Compaq Presario 5700 Series Personal Computers.
Adherence to the procedures and precautions described in this chapter is essential for
proper service.
The topics
discussed in this section include the following:
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 (ESD) may not be affected at all
and will work perfectly throughout a normal cycle. Or it may function normally for a
while, then degrade in the internal layers, reducing its life expectancy.
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.
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The accompanying
table shows typical electrostatic voltages generated by different activities.
Typical Electrostatic Voltages |
|
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 tubes |
2,000
V |
700 V |
400 V |
Removing
DIPS from vinyl trays |
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 PCBs |
26,000
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. |
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Many electronic
components are sensitive to ESD. Circuitry design and structure determine the degree of
sensitivity. The following proper packaging and grounding precautions are necessary to
prevent damage:
- Protect all electrostatic parts
and assemblies with conductive or approved containers or packaging.
- Keep electrostatic sensitive
parts in their containers until they arrive at static-free stations.
- 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
electronic-sensitive parts from assemblies in protective packaging or conductive foam.
- Use transporters and conveyors
made of antistatic belts and metal roller bushings. Mechanized equipment used for moving
materials must be wired to ground and proper materials selected to avoid static charging.
When grounding is not possible, use an ionizer to dissipate electric charges.
The accompanying
table shows typical static-shielding protection levels afforded by different protective
packaging materials.
Static-Shielding Protection Levels |
Method |
Voltages |
Antistatic
Plastic |
1,500 |
Carbon-Loaded
Plastic |
7,500 |
Metallized
Laminate |
15,000 |
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To prevent static
damage to hard drives, use the following precautions:
- Handle drives gently, using
static-guarding techniques.
- Store drives in the original
shipping containers.
- Avoid dropping drives from any
height onto any surface.
- Handle drives on surfaces that
have at least one inch of shock-proof foam.
- Always place drives PCB assembly
side down on the foam.
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The method for
grounding must include a wrist strap or a foot strap at a grounded workstation. When
seated, wear a wrist strap connected to a grounded system. When standing, use footstraps
and a grounded floor mat.
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Grounding Workstations
To prevent static
damage at the workstation, use the following precautions:
- Cover the workstation with
approved static-dissipative material.
- Provide a wrist strap connected
to the work surface and properly grounded tools and equipment.
- Use static-dissipative mats,
heel straps, or air ionizers to give added protection.
- Handle electrostatic sensitive
components, parts, and assemblies by the case or PCB laminate. Handle them only at
static-free workstations.
- Avoid contact with pins, leads,
or circuitry.
- Turn off power and input signals
before inserting and removing connectors or test equipment.
- Use fixtures made of static-safe
materials when fixtures must directly contact dissipative surfaces.
- Keep work area free of
nonconductive materials such as ordinary plastic assembly aids and Styrofoam.
- Use field service tools, such as
cutters, screwdrivers, vacuums, that are conductive.
- Use a portable field service kit
with a static dissipative vinyl pouch that folds out of a work mat. Also use a wrist strap
and a ground cord for the work surface. Ground the cord to the chassis of the equipment
undergoing test or repair.
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Use the following
equipment to prevent static electricity damage to the equipment:
- Wrist Straps are flexible straps with a minimum of 1 mega ohm +/- 10% resistance to the ground cords. To provide proper
ground, a strap must be worn snug against the skin. On grounded mats without banana-plug
connectors, connect a wrist strap with alligator clips.
- Heelstraps/Toestraps/Bootstraps can be used at standing
workstations and are compatible with most types of boots and shoes. On conductive floors
or dissipative floor mats, use them on both feet with a minimum of 1 mega ohm resistance between operator and ground. To be effective,
the conductive strips must be worn in contact
with the skin.
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Other materials
and equipment that are recommended for use in preventing static electricity include:
- Antistatic tape
- Antistatic smocks, aprons, or
sleeve protectors
- Conductive bins, and other
assembly or soldering aids
- Conductive foam
- Conductive tabletop workstations with ground cord of 1 mega ohm
of resistance
- Static dissipative table or
floor mats with hard tie to ground
- Field service kits
- Static awareness labels
- Wrist straps and footwear straps providing 1 mega ohm (+/- 10%) resistance
- Material handling packages
- Conductive plastic bags
- Conductive plastic tubes
- Conductive tote boxes
- Metal tote boxes
- Opaque shielding bags
- Transparent metallized shielding
bags
- Transparent shielding tubes
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- Torx T-8, T-10, and T-15
screwdrivers (included in kit number 130619-001)
- Needle-nose pliers
- Flat-bladed screwdriver
- Diagnostics software
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The screws used in
these products are not interchangeable. If an incorrect screw is used during the
reassembly process, it could cause damage to the unit. Compaq strongly recommends that all
screws removed during the disassembly process be kept with the part that was removed, then
returned to their proper locations.
IMPORTANT: |
As each subassembly is removed from the computer, it should be placed
away from the work area to prevent damage |
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Most cables used
throughout the unit are ribbon cables (Figures 4-1, 4-2, 4-3, 4-4, and 4-5). These cables
must be handled with extreme care to avoid damage.
Apply only the
tension required to seat or unseat the cables during insertion or removal from the
connector. Handle cables by the connector whenever possible. In all cases, avoid bending,
twisting, or tearing the cables, and ensure that cables are placed in such a way that they
cannot be caught or snagged by parts being removed or replaced.
The numbered
cables show the recommended configuration for the ribbon cables. The shaded lines indicate
alternative configurations for additional optional hard drives, tape drives, and diskette
drives.

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CAUTION: When servicing these
computers, ensure that cables are placed in their proper location during the reassembly
process. Improper cable placement can cause severe damage to the unit. |
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