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3
Routine care, SATA drive guidelines, and
disassembly preparation
This chapter provides general service information for the computer. Adherence to the procedures and
precautions described in this chapter is essential for proper service.
CAUTION:
When the computer is plugged into an AC power source, voltage is always applied to the system
board. The power cord must be disconnected from the power source before opening the computer to prevent
system board or component damage.
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 appear to be affected at all and can work perfectly throughout a normal
cycle. The device may function normally for a while, but it has been degraded 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
The following table shows how humidity affects the electrostatic voltage levels generated by different activities.
A product can be degraded by 700 V.
Different activities generate different amounts of static electricity.
●
Static electricity increases as humidity decreases.
●
Table 3-1
Static electricity occurrence based on activity and humidity
Event
Walking across carpet
Walking across vinyl floor
Motions of bench worker
Removing DIPs from plastic tube
Removing DIPs from vinyl tray
Removing DIPs from Styrofoam
Removing bubble pack from PCB
Packing PCBs in foam-lined box
Relative Humidity
55%
40%
7,500 V
15,000 V
3,000 V
5,000 V
400 V
800 V
400 V
700 V
2,000 V
4,000 V
3,500 V
5,000 V
7,000 V
20,000 V
5,000 V
11,000 V
Electrostatic discharge information
10%
35,000 V
12,000 V
6,000 V
2,000 V
11,500 V
14,500 V
26,500 V
21,000 V
25
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