Follow the safety precautions described in the following sections
when you perform an installation or a disassembly/reassembly procedure:
Turn off the system and all attached peripherals.
Disconnect the system and all attached peripherals
from AC power, and then remove the battery.
Disconnect all network cables, telephone or telecommunications
lines from the system.
Use a wrist grounding strap and mat when working
inside any computer system to avoid electrostatic discharge (ESD)
damage.
After removing a system component, carefully place
the removed component on an anti-static mat.
Wear shoes with non-conductive rubber soles to help
reduce the risk of being shocked or seriously injured in an electrical
accident.
Dell products with standby power must
be completely unplugged before the case is opened. Systems that incorporate
standby power are essentially powered while turned off. The internal
power enables the system to be remotely turned on (wake on LAN), suspended
into a sleep mode, and have other advanced power management features.
After you unplug a system and before you remove components,
wait approximately 30 to 45 seconds to allow the charge to drain from
the circuits.
Bonding
Bonding is a method for connecting two or more grounding
conductors to the same electrical potential. This is done through
the use of a Field Service ESD kit. When connecting a bonding wire,
always ensure that it is connected to bare metal and never to a painted
or non-metal surface. The wrist strap should be secure and in full
contact with your skin, and be sure to always remove all jewelry such
as watches, bracelets, or rings prior to bonding yourself and the
equipment.
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parts are no longer applicable.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.
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.
Handle all static-sensitive components in a static-safe
area. If possible, use anti-static floor pads and workbench pads.
When handling static-sensitive components, grasp them
by the sides, not the top. Avoid touching pins and circuit boards.
When unpacking a static-sensitive component from its
shipping carton, do not remove the component from the anti-static
packing material until you are ready to install the component. Before
unwrapping the anti-static packaging, be sure to discharge static
electricity from your body.
Before transporting a static-sensitive component,
place it in an anti-static container or packaging.
The ESD Field Service
Kit
The unmonitored Field Service kit is the
most commonly used. Each Field Service kit includes three main components:
anti-static mat, wrist strap, and bonding wire.
The anti-static mat is dissipative and should be used
to safely place parts on during service procedures. When using an
anti-static mat, your wrist strap should be snug and the bonding wire
should be connected to the mat and to bare-metal on the system being
worked on. Once deployed properly, service parts can be removed from
the ESD bag and placed directly on the mat. Remember, the only safe
place for ESD-sensitive items are in your hand, on the ESD mat, in
the system, or inside a bag.
The wrist strap and bonding wire can be either directly
connected between your wrist and bare metal on the hardware if the
ESD mat is not required, or connected to the anti-static mat to protect
hardware that is temporarily placed on the mat. The physical connection
of the wrist strap and bonding wire between your skin, the ESD mat,
and the hardware is known as bonding. Use only Field Service kits
with a wrist strap, mat, and bonding wire. Never use wireless wrist
straps.
Always be aware that the internal wires
of a wrist strap are prone to damage from normal wear and tear, and
must be checked regularly with a wrist strap tester in order to avoid
accidental ESD hardware damage. It is recommended to test the wrist
strap and bonding wire a minimum of once per week.
Table 1. Wrist StrapsThe following shows a wrist strap and bonding wire
and a wireless ESD strap.
Wrist Strap and Bonding Wire
Wireless ESD Strap (Unacceptable)
ESD Wrist Strap Tester
The wires inside of an ESD strap are prone to damage
over time. When using an unmonitored kit, it is best practice to regularly
test the strap prior to each service call, and at a minimum, test
once per week. A wrist strap tester is the best method for doing this
test. If you do not have your own wrist strap tester, check with your
regional office to find out if they have one. To perform the test,
plug the wrist-strap’s bonding-wire into the tester while it is strapped
to your wrist and push the button to test. A green LED is lit if the
test is successful; a red LED is lit and an alarm sounds if the test
fails.
Insulator Elements
It is critical to keep ESD sensitive devices, such
as plastic heat sink casings, away from internal parts that are insulators
and often highly charged.
Table 2. Placement of
Insulator ElementsThe following shows unacceptable and acceptable
placement for insulator parts relative to ESD sensitive devices.
Unacceptable — DIMM
lying on an insulator part (plastic heat sink shroud)
Acceptable — DIMM
separated from the insulator part
Consider the Working
Environment
Before deploying the ESD Field
Service kit, assess the situation at the customer location. For example,
deploying the kit for a server environment is different than for a
desktop or portable environment. Servers are typically installed in
a rack within a data center; desktops or portables are typically placed
on office desks or cubicles.
Always look for a
large open flat work area that is free of clutter and large enough
to deploy the ESD kit with additional space to accommodate the type
of system that is being repaired. The workspace should also be free
of insulators that can cause an ESD event. On the work area, insulators
such as Styrofoam and other plastics should always be moved at least
12 inches or 30 centimeters away from sensitive parts before physically
handling any hardware components.
ESD Packaging
All ESD-sensitive devices must be shipped and received
in static-safe packaging. Metal, static-shielded bags are preferred.
However, you should always return the damaged part using the same
ESD bag and packaging that the new part arrived in. The ESD bag should
be folded over and taped shut and all the same foam packing material
should be used in the original box that the new part arrived in.
ESD-sensitive devices should be removed from packaging
only at an ESD-protected work surface, and parts should never be placed
on top of the ESD bag because only the inside of the bag is shielded.
Always place parts in your hand, on the ESD mat, in the system, or
inside an anti-static bag.
Transporting Sensitive
Components
When transporting ESD-sensitive
components such as replacement parts or parts to be returned to Dell,
it is critical to place these parts in anti-static bags for safe transport.
ESD Protection Summary
It is strongly suggested that all field service engineers
use the traditional wired ESD grounding wrist strap and protective
anti-static mat at all times when servicing Dell products. In addition,
it is critical that engineers keep sensitive parts separate from all
insulator parts while performing service and that they use anti-static
bags for transporting sensitive components.
Lifting Equipment
NOTE Do not lift greater than 50 pounds.
Always obtain assistance from another person or persons, or use a
mechanical lifting device.
Adhere to the following
guidelines when lifting equipment:
Get a firm balanced footing. Keep your feet apart
for a stable base, and point your toes out.
Bend your knees. Do not bend at the waist.
Tighten stomach muscles. Abdominal muscles support
your spine when you lift, offsetting the force of the load.
Lift with your legs, not your back.
Keep the load close. The closer it is to your spine,
the less force it exerts on your back.
Keep your back upright, whether lifting or setting
down the load. Do not add the weight of your body to the load. Avoid
twisting your body and back.
Follow the same techniques in reverse to set the load
down.
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