Removal And Replacement; Generating Static; Preventing Electrostatic Damage To Equipment; Grounding Methods - Compaq Presario 3500 Series Maintenance & Service Manual

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Maintenance & Service Guide
Presario 3500 Series Personal Computers
| Preface | Product Description
Removal & Replacement
| Specifications

Removal and Replacement

This chapter provides general service information for Compaq Presario
3500 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:
Electrostatic Discharge

Generating Static

Preventing Electrostatic Damage to Equipment

Preventing Damage to Drives

Grounding Methods

Grounding Workstations

Grounding Equipment

Recommended Materials and Equipment

Tool Requirements
Screws

Cables and Connectors

Electrostatic Discharge
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.
Top
Generating Static
The accompanying table shows typical electrostatic voltages generated by
different activities.
Event
Walking across carpet
Walking across vinyl floor
Motions of bench worker
Removing DIPS from plastic tubes
Removing DIPS from vinyl trays
Removing DIPS from Styrofoam
Removing bubble pack from PCBs
Packing PCBs in foam-lined box
NOTE: 700 volts can degrade a product.
Top
Preventing Electrostatic Damage to Equipment
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.
Method
Antistatic Plastic
Carbon-Loaded Plastic
Metallized Laminate
Top
Preventing Damage to Drives
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.
Top
Grounding Methods
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.
Top
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.
Top
Grounding Equipment
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
ground. To be effective, the conductive strips must be worn in contact
with the skin.
Top
Recommended Materials and Equipment
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
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
Top
Tool Requirements
Torx T-8, T-10, and T-15 screwdrivers (included in kit number
130619-001)
Needle-nose pliers
Flat-bladed screwdriver
Diagnostics software
Top
Screws
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.
As each subassembly is removed from the computer, it should be
IMPORTANT:
placed away from the work area to prevent damage
Top
Cables and Connectors
Most cables used throughout the unit are ribbon cables. 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.
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.
Top
| Troubleshooting
| Connector Pins
Typical Electrostatic Voltages
Static-Shielding Protection Levels
Voltages
1,500
7,500
15,000
resistance between operator and
| Illustrated Parts
| Power Cord Requirements
Relative Humidity
10% 40%
35,000 V 15,000 V 7,500 V
12,000 V 5,000 V
6,000 V 800 V
2,000 V 700 V
11,500 V 4,000 V
14,500 V 5,000 V
26,000 V 20,000 V 7,000 V
21,000 V 11,000 V 5,000 V
|
55%
3,000 V
400 V
400 V
2,000 V
3,500 V
+/-
(+/- 10%)