Compaq Deskpro 1000 Series of Personal Computers
4-1
chapter
4
R
EMOVAL AND
R
EPLACEMENT
P
RELIMINARIES
This chapter provides general service information for the computer. Adherence to the procedures
and precautions described in this chapter is essential for proper service.
4.1
Electrostatic Discharge Information
A sudden discharge of static electricity from your 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 can
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.
4.1.1
Generating Static
Table 4-1 shows how different activities generate static electricity at different electrostatic voltage
levels.
Table 4-1
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 tube
2,000 V
700 V
400 V
Removing DIPs* from vinyl tray
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 PCB
26,500 V
20,000 V
7,000 V
Packing PCBs in foam-lined box
21,000 V
11,000 V
5,000 V
*Dual Inline Packaging (DIP) is the packaging around individual microcircuitry. These are then multi-
packaged inside plastic tubes, trays, or Styrofoam.
✎
700 volts can degrade a product.
