Dell Latitude 3310, Руководство по обслуживанию

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Electrostatic Discharge 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 earlier
Dell products. For this reason some previously approved methods of handling parts are no longer applicable.
There are two recognized types of ESD damage: catastrophic and intermittent failures.
• Catastrophic —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.
NOTE: Catastrophic failures represent approximately 20 percent of ESD-related failures.
• Intermittent —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.
NOTE: 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 more difficult type of damage to recognize and troubleshoot is the intermittent (also called latent or “walking wounded”) failure. The
following image shows an example of intermittent damage to a memory DIMM trace. Although the damage is done, the symptoms may
not become an issue or cause permanent failure symptoms for some time after the damage occurs.
Figure 2. Intermittent (Latent) Damage to a Wiring Trace
Do the following 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.
Figure 3. Chassis "Bare Metal" Grounding (Unacceptable)
8 Working on your computer