Chapter 5. Removal And Replacement Procedures; Chapter 5.1 Electrostatic Discharge - Compaq 486 Maintenance And Service Manual

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.
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.
neither felt nor heard, but damage occurs.
electrostatic discharge (ESD) may not be affected at all and will work
perfectly throughout a normal cycle.
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
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Event
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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
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NOTE: 700 volts can degrade a product.
Preventing Electrostatic Damage to Equipment
Many electronic components are sensitive to ESD.
structure determine the degree of sensitivity.
Refer to the SUPPORT
Often the spark is
An electronic device exposed to
Or it may function normally for awhile,
Relative Humidity
10% 40%
35,000V 15,000V
12,000V 5,000V
6,000V 800V
2,000V 700V
11,500V 4,000V
14,500V 5,000V
26,000V 20,000V
21,000V 11,000V
Circuitry design and
Proper packaging and
55%
7,500V
3,000V
400V
400V
2,000V
3,500V
7,000V
5,000V