Safety Precautions; Electrostatic Discharge-Esd Protection - Dell OptiPlex XE3 Tower Service Manual

NOTE: If you are using a different operating system, see the documentation of your operating system for shut-down
instructions.
3. Disconnect your computer and all attached devices from their electrical outlets.
4. Disconnect all attached network devices and peripherals, such as keyboard, mouse, and monitor from your computer.
5. Remove any media card and optical disc from your computer, if applicable.
6. After the computer is unplugged, press and hold the power button for 5 seconds to ground the system board.
CAUTION: Place the computer on a flat, soft, and clean surface to avoid scratches on the display.
7. Place the computer face down.

Safety precautions

The safety precautions chapter details the primary steps to be taken before performing any disassembly instructions.
Observe the following safety precautions before you perform any installation or break/fix procedures involving disassembly or
reassembly:
● Turn off the tablet and all attached peripherals.
● Disconnect the tablet and all attached peripherals from AC power.
● Disconnect all network cables, telephone, and telecommunications lines from the system.
● Use an ESD field service kit when working inside any tablet to avoid electrostatic discharge (ESD) damage.
● After removing any system component, carefully place the removed component on an antistatic mat.
● Wear shoes with nonconductive rubber soles to reduce the chance of getting electrocuted.
Bonding
Bonding is a method for connecting two or more grounding conductors to the same electrical potential. This is done by using a
field service electrostatic discharge (ESD) kit. When connecting a bonding wire, ensure that it is connected to bare metal and
never to a painted or nonmetal surface. The wrist strap should be secure and in full contact with your skin, and ensure that you
remove all jewelry such as watches, bracelets, or rings prior to bonding yourself and the equipment.
Electrostatic discharge—ESD protection
ESD is a major concern when you handle electronic components, especially sensitive components such as expansion cards,
processors, memory DIMMs, and system boards. Very slight charges can damage circuits in ways that may not be obvious, such
as intermittent problems or a shortened product life span. As the industry pushes for lower power requirements and increased
density, ESD protection is an increasing concern.
Due to the increased density of semiconductors used in recent Dell products, the sensitivity to static damage is now higher than
in previous Dell products. For this reason, some previously approved methods of handling parts are no longer applicable.
Two recognized types of ESD damage are catastrophic and intermittent failures.
● Catastrophic – Catastrophic failures represent approximately 20 percent of ESD-related failures. The damage causes
an immediate and complete loss of device functionality. An example of catastrophic failure is a memory DIMM that has
received a static shock and immediately generates a "No POST/No Video" symptom with a beep code emitted for missing or
nonfunctional memory.
● Intermittent – Intermittent failures represent approximately 80 percent of ESD-related failures. The high rate of
intermittent failures means that most of the time when damage occurs, it is not immediately recognizable. The DIMM
receives a static shock, but the tracing is merely weakened and does not immediately produce outward symptoms related to
the damage. The weakened trace may take weeks or months to melt, and in the meantime may cause degradation of memory
integrity, intermittent memory errors, etc.
The more difficult type of damage to recognize and troubleshoot is the intermittent (also called latent or "walking wounded")
failure.
Perform the following steps to prevent ESD damage:
● Use a wired ESD wrist strap that is properly grounded. The use of wireless anti-static straps is no longer allowed; they do not
provide adequate protection. Touching the chassis before handling parts does not ensure adequate ESD protection on parts
with increased sensitivity to ESD damage.
● Handle all static-sensitive components in a static-safe area. If possible, use anti-static floor pads and workbench pads.
Working on your computer 7