Compaq 1500 Anleitung zur Fehlerbehebung PDF herunterladen (Seite 79)

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Chapter 6

Removal and Replacement Preliminaries 6-1

Removal and Replacement

Preliminaries

This chapter provides general service information for the Compaq Armada 1500 Family

of Personal Computers. Adherence to the procedures and precautions described in this

chapter is essential for proper service.

6.1 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 or 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.

Generating Static

Table 6-1 shows how different activities generate static electricity and at different

electrostatic voltage levels.

Table 6-1

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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Compaq 1500 Anleitung zur Fehlerbehebung Seite 79