A+ Guide to Managing and Maintaining Your PC
Fifth Edition
Chapter 4
Electricity and Power
Supplies

You Will Learn…
 How electricity is measured
 How to protect your computer system against damaging changes in electrical power
 About different form factors and computer cases
 How to detect and correct power supply problems
 About Energy Star specifications
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Measures of Electricity
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AC and DC
 Alternating current (AC)

Cycles back and forth

Economical
 Direct current (DC)

Travels in only one direction, from hot to ground

Required by most electronic devices
 Computer power supply functions as both a transformer and rectifier
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Computer Power Supply
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Hot, Neutral, and Ground
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Hot, Neutral, and Ground
( continued
)
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Hot, Neutral, and Ground
( continued
)
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Common Electrical Components
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Protecting Your Computer
System: General Precautions
 Make notes so you can backtrack
 Remove packing materials from work area
 Keep components away from hair and clothing
 Keep screws and spacers in an orderly place

Don’t stack boards on top of each other
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Protecting Your Computer
System: General Precautions
( continued
)

Don’t touch chips on motherboard or expansion cards

Don’t touch chip with magnetized screwdriver

Don’t change DIP switch settings with a graphite pencil
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Protecting Your Computer
System: General Precautions
( continued
)
 Have classroom instructor check your work before putting cover on and powering up
 Turn off a computer before moving it
 Keep disks away from magnetic fields, heat, and extreme cold
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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 or static strap

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 or on same circuit as high-powered electrical equipment

Use line conditioners
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Surge Protection and Battery
Backup
 Surge suppressors
 Power conditioners
 Uninterruptible power supplies (UPSs)
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Uninterruptible Power Supplies
 Benefits

Condition line for brownouts and spikes

Provide backup power during a blackout

Protect against very high potentially damaging spikes
 Considerations

Cost

UPS rating

Degree of line conditioning

Warranty and service policies
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UPS
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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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Case, Power Supply, and
Motherboard Form Factors
 AT
 ATX (most popular)
 LPX
 NLX
 Backplane systems
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AT Form Factor
 Used on older motherboards
 Difficult to install, service, and upgrade

Uses two power connectors:
P8 and P9

Problematic position of CPU in relation to expansion slots
 No longer produced by most manufacturers
Baby AT Form Factor
 Industry standard from
1993-1997
 Small; fits into many types of cases
 Problematic position of CPU unresolved
 Drives/devices not close to connections on motherboard
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ATX Form Factor
 Open, nonproprietary spec (Intel 1995)
 Easier to add and remove components
 Greater support for I/O devices and processor technology
 Lower costs
 Improved positioning of components
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ATX Form Factor ( continued
)
 Smaller
 Uses one power connector: P1
 Soft switch feature
 Better air circulation
 Other types: Mini-ATX, MicroATX, FlexATX
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ATX Motherboard
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NLX Form Factor
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Other Form Factors
LPX and Mini-LPX Backplane Systems
 Riser card similar to
NLX systems
 Used in low-cost systems
 Difficult to upgrade
 Cannot handle size and operating temperature of processors
 Proprietary issues
 Not a true motherboard; board sits against back of proprietary case with slots for other cards
 Active backplanes
 Passive backplanes
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Types of Cases
 Desktop cases
 Tower cases

Minitower

Midsize tower

Full-size tower
 Notebook cases
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Desktop Case
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Tower Case
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Tower and Desktop Cases
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Upgrading Your Power Supply
 Sometimes necessary when you add new devices
 Easiest way to fix a power supply you suspect is faulty is to replace it
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Introduction to Troubleshooting
 Isolate the problem

Problems that prevent PC from booting

Problems that occur after a successful boot
 Learn as much as you can by asking questions of user(s)
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PC Problem Solving
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Troubleshooting the Power
System: General Guidelines
 Any burnt parts or odors?
 Everything connected and turned on? Loose cable connections? Computer plugged in?
 All switches turned on? Wall outlet good?
 If fan is not running, turn off computer:
Connections to power supply secure? Cards securely seated?
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Troubleshooting the Power
System: General Guidelines
( continued
)
 Check for correct wire connections to motherboard
 Remove nonessential expansion cards one at a time
 Vacuum entire unit
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Troubleshooting an ATX Power
Supply
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Troubleshooting the Power
System
 Power supply itself
 Power supply fan
 Power problems with the motherboard
 Overheating
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Preventing Overheating
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Preventing Overheating
( continued
)
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Energy Star Systems
(The Green Star)
 Satisfy energy-conserving standards of the US
EPA
 Generally have a standby program that switches device to sleep mode when not in use
 Apply to computers, monitors, printers, copiers, and fax machines
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Power Management Methods
 Advanced Power Management (APM)
 AT Attachment (ATA) for IDE drives
 Display Power Management Signaling
(DPMS) standards for monitors and video cards
 Advanced Configuration and Power Interface
(ACPI)
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Power Management Features
 Green timer on the motherboard
 Doze time
 Standby time
 Suspend time
 Hard drive standby time
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Power Management Setup
Screen
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Energy Star Monitors
 Most adhere to DPMS specifications

Allow video card and monitor to go into sleep mode simultaneously
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Changing Power Options
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Summary
 Measurements of electricity
 Form in which electricity comes to you as house current
 The power supply, backup power sources, and how to change a defective power supply
 Form factors
 How Energy Star saves energy
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