Hardware Reference
In-Depth Information
use expansion slot brackets. Many mid-range and high-performance cards have cooling
shrouds wide enough to prevent use of the adjacent expansion slot.
Electrostatic Discharge Protection
When you are working on the internal components of a computer, you must take the ne-
cessaryprecautionstopreventaccidentalstaticdischargestothecomponents.Atanytime,
your body can hold a large static voltage charge that can easily damage components of
your system. Before I ever put my hands into an open system, I touch a bare metal groun-
dedportionofthechassis,suchastheinternalframeorthepowersupplycase.Thisaction
servestoequalizetheelectricalchargesthatthedeviceandmybodymightbecarrying.Be
sure the system is unplugged during all phases of the assembly process. Some will claim
that you should leave the system plugged in to provide an earth ground through the power
cordandoutlet,butthatisunnecessary.Ifyouleavethesystempluggedin,youopenyour-
selfuptootherproblems,suchasaccidentallyturningitonorleavingitonwheninstalling
a board or device, which can damage the motherboard or other devices.
Caution
Also note that power supplies used in many systems today deliver a +5V current to the
motherboard continuously—that is, whenever they are plugged in. Bottom line: Be sure any
system you are working on is completely unplugged from the wall outlet.
Amoresophisticatedwaytoequalizethechargesbetweenyouandanyofthesystemcom-
ponents is to use an electrostatic discharge (ESD) protection kit. These kits consist of a
wrist strap and mat, with ground wires for attachment to the system chassis. When you
are going to work on a system, you place the mat next to the system unit. Next, you clip
the ground wire to both the mat and an unpainted part of the system's chassis, tying the
grounds together. You then put on the wrist strap and attach that wire to either the chassis
or the mat. If you are using a wrist strap without a mat, clip the wrist-strap wire to the
systemchassis.Whenclippingthesewirestothechassis,besuretouseanareathatisfree
of paint so a good ground contact can be achieved. This setup ensures that any electrical
charges are carried equally by you and any of the components in the system, preventing
the sudden flow of static electricity that can damage the circuits.
As you install or remove drives, adapter cards, and especially delicate items such as the
entire motherboard, memory modules, or processors, you should place these components
on the static mat. Sometimes people put the system unit on top of the mat, but the unit
should be alongside the mat so you have room to lay out all the components as you work
with them. If you are going to remove the motherboard from a system, be sure you leave
enough room for it on the mat.
