A+ Guide to Managing
and Maintaining Your PC
Fifth Edition
Chapter 4
Electricity and Power
Supplies
Protecting Yourself Against
Electricity

Turn off power and unplug computer

Always use a ground bracelet

Never touch inside of a computer while it is
turned on

Never remove cover or put your hands inside
monitor or power supply
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Static Electricity (or ESD)

Can cause catastrophic failure or upset failure

Protection against ESD

Ground bracelet / Ground mats

Static shielding bags
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Ground Bracelet
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Ground Bracelet with a Ground
Mat
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Static Shielding Bags
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EMI (Electromagnetic
Interference)

Caused by magnetic field produced as side
effect when electricity flows

Protection against EMI

Cover expansion slots

Do not place system close to high-powered
electrical equipments
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Computer Power Supply
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Power Consumption


Measured in watts, volt-amperes (VA), or
kilovolt-amperes (kVA)
The power consumption of a computer is
mainly determined by





CPU: 60w – 100 w
Graphical card (3D): 60w – 70w
Hard drive
CD-RW/DVD
Motherboard: 20 (30)w
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Ventilation

Forms an air flow that circulates (front to end,
bottom to top)
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Power Management


Energy Start (The Green Start) systems: satisfy
certain energy-conserving standards of the
U.S. Environmental Protection Agency
Switches to different levels of sleep mode
when not in use


BIOS
Operating System
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Power Management Setup
Screen
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Changing Power Options
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Surge Protection and Battery
Backup



Surge suppressors – protect equipment from
overvoltages on AC power lines
Power conditioners – regulate the power,
providing continuous voltage during
brownouts
Uninterruptible power supplies (UPSs) –
provides backup power in a blackout to allow
time for backing up important data
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UPS
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UPS

Standby UPS (off-line)


Line interactive UPS


powers equipment directly from the AC outlet. The
batteries are used when the power fails, but with a small
delay
provides a voltage boost on sags without accessing the
batteries.
On-line UPS

Conditions incoming power, and there is no delay to switch
to battery.
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Purchasing a UPS




Cost
UPS rating (power support)
Degree of line conditioning
Warranty and service policies
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The Computer Case and Form
Factors

Form factor describes size, shape, and general
makeup of a hardware component

Use same form factor for motherboard, case,
and power supply

Decision driven by motherboard
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ATX Motherboard
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ATX vs. AT Form Factors


Power connectors
Soft switch vs. hard switch
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Power Connectors on AT and
ATX Boards
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Other Form Factors


NLX/LPX – uses a riser card
Backplane – for rack-mounted systems
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NLX Form Factor
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Troubleshooting the Power
System

Symptoms



The power supply fan is not spinning
The computer resets/stalls
Troubleshooting by substituting
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Case Study

Symptom

Whenever playing a game, the computer stalls
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Case Study

Symptom

Whenever running a particular program for about
two hours, the computer reboots
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Hands-on Projects


Taking apart a computer and putting it back
together
Changing a power supply
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