Routine care, drive guidelines, and
disassembly preparation
3
This information provides general service information for the computer. Adherence to the procedures
and precautions is essential for proper service.
IMPORTANT: When the computer is plugged into an AC power source, DC voltage is always applied to
the system board. You must disconnect the power cord from the power source before opening the
computer to prevent electric shock, 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) might not appear to be affected at all and
can work perfectly throughout a normal cycle. The device might 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.
IMPORTANT: To prevent damage to the device when you are removing or installing internal
components, observe these precautions:
● Keep components in their electrostatic-safe containers until you are ready to install them.
● Before touching an electronic component, discharge static electricity by using the guidelines
described in this section.
● Avoid touching pins, leads, and circuitry. Handle electronic components as little as possible.
● If you remove a component, place it in an electrostatic-safe container.
Generating static electricity
This table shows how humidity affects the electrostatic voltage levels generated by different activities. A
product can be degraded by 700 V of static electricity.
● 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
Relative humidity
Event 55% 40% 10%
8 Chapter 3 Routine care, drive guidelines, and disassembly preparation
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