HP Portable 486 Compaq Portable 486c Personal Computer Maintenance and Service - Page 54

Removal and Replacement Procedures, Introduction, Electrostatic Discharge

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Chapter 5. Removal and Replacement Procedures Introduction This chapter provides module level removal and replacement procedures for the COMPAQ PORTABLE 486c Personal Computer. After completing all removal and replacement procedures, run the Diagnostics program to verify that all components operate properly. Refer to the SUPPORT SOFTWARE MAINTENANCE AND SERVICE GUIDE for information on installing new or updated utilities when adding or removing options. Chapter 5.1 Electrostatic Discharge Before beginning to remove and replace a component in the COMPAQ PORTABLE 486c Personal Computer, be sure you are discharged of static electricity. A sudden discharge of static electricity from a finger or other conductor can destroy static sensitive devices or micro circuitry. 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 awhile, 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 and/or melt silicon junctions. Generating Static Table 5-1 shows how different methods generate static electricity and at different electrostatic voltage levels. Table 5-1. Typical Electrostatic Voltages Event Relative Humidity 10% 40% 55% Walking across carpet 35,000V 15,000V 7,500V Walking across vinyl floor 12,000V 5,000V 3,000V Motions of bench worker 6,000V 800V 400V Removing DIPs from plastic tubes 2,000V 700V 400V Removing DIPs from vinyl trays 11,500V 4,000V 2,000V Removing DIPs from Styrofoam 14,500V 5,000V 3,500V Removing bubble pack from PCBs 26,000V 20,000V 7,000V Packing PCBs in foam lined box 21,000V 11,000V 5,000V NOTE: 700 volts can degrade a product. Preventing Electrostatic Damage to Equipment Many electronic components are sensitive to ESD. Circuitry design and structure determine the degree of sensitivity. Proper packaging and

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Chapter 5. Removal and Replacement Procedures
Introduction
This chapter provides module level removal and replacement procedures for the
COMPAQ PORTABLE 486c Personal Computer.
After completing all removal and replacement procedures, run the Diagnostics
program to verify that all components operate properly. Refer to the SUPPORT
SOFTWARE MAINTENANCE AND SERVICE GUIDE for information on installing new or
updated utilities when adding or removing options.
Chapter 5.1 Electrostatic Discharge
Before beginning to remove and replace a component in the COMPAQ PORTABLE
486c Personal Computer, be sure you are discharged of static electricity.
A sudden discharge of static electricity from a finger or other conductor can
destroy static sensitive devices or micro circuitry. 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 awhile,
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
and/or melt silicon junctions.
Generating Static
Table 5-1 shows how different methods generate static electricity and at
different electrostatic voltage levels.
Table 5-1. Typical Electrostatic Voltages
=============================================================================
Event
Relative Humidity
10%
40%
55%
-----------------------------------------------------------------------------
Walking across carpet
35,000V
15,000V
7,500V
Walking across vinyl floor
12,000V
5,000V
3,000V
Motions of bench worker
6,000V
800V
400V
Removing DIPs from plastic tubes
2,000V
700V
400V
Removing DIPs from vinyl trays
11,500V
4,000V
2,000V
Removing DIPs from Styrofoam
14,500V
5,000V
3,500V
Removing bubble pack from PCBs
26,000V
20,000V
7,000V
Packing PCBs in foam lined box
21,000V
11,000V
5,000V
=============================================================================
NOTE: 700 volts can degrade a product.
Preventing Electrostatic Damage to Equipment
Many electronic components are sensitive to ESD. Circuitry design and
structure determine the degree of sensitivity. Proper packaging and