Title: A Guide to Managing and Maintaining your PC, 6e
1A Guide to Managing and Maintaining your PC, 6e
- Chapter 4
- Form Factors and Power Supplies
2Objectives
- Learn about different form factors and computer
cases - Learn how electricity is measured
- Learn how to protect your computer system against
damaging changes in electrical power - Learn about Energy Star specifications
- Learn how to troubleshoot electrical problems
3Introduction
- Power supply passes power to PC components
- Elements driving type of power supply used in a
PC - The motherboard
- The form factor of the computer case
- Energy Star devices designed to save energy
- Electricity topics covered
- Measurements of electricity
- How electricity is delivered
- Protecting a PC from electrical damage
- Changing a defective power supply
4Computer Case, Motherboard, and Power Supply Form
Factors
- Form factor
- Specifies size, shape, features of a hardware
device - Form factor for motherboard is chosen first
- Same form factor is used for case and power
supply - Using the same form factor assures you that
- The motherboard fits the case
- The powers supply cords provide proper voltage
- Holes in the motherboard align with holes in the
case - Holes in the case align with ports off the
motherboard - Wires on the case match connections on motherboard
5Types of Form Factors
- AT (Advanced Technology) form factor
- Specified motherboard dimensions of 12 x 13.8
- Utilized by IBM AT PC in the 1980s
- Baby AT form factor
- Specified motherboard dimensions of 13 x 8.7
- Industry standard form factor from 1993 to 1997
- ATX form factor
- Specified motherboard dimensions of 12 x 9.6
- Open specification that is most commonly used
today - Includes all AT voltages plus a 3.3-volt circuit
6Figure 4-4 The CPU on an ATX motherboard sits
opposite the expansion slots and does not block
the room needed for long expansion cards
7Types of Form Factors (continued)
- MicroATX form factor
- Reduces number of I/O slots on the motherboard
- BTX (Balanced Technology Extended) form factor
- Focuses on reducing heat and supporting
motherboard - LPX and Mini-LPX form factors
- Designed for low-end PC motherboards
- NLX form factor
- Developed to improve the LPX form factor
- Backplane Systems (Active and Passive)
- Use boards with slots, but little or no circuitry
8Figure 4-8 Improved airflow in a BTX case and
motherboard makes it unnecessary to have a fan on
top of the processor
9Types of Cases
- Computer case (chassis)
- Houses power supply, motherboard, cards, drives
- Panel switches/lights are used to control/monitor
PC - Desktop cases
- Motherboard on the bottom, power supply to the
rear - Tower cases
- Are up to 2 feet high and can contain several
drives - Notebook cases
- Used for all portables and have desktop
components
10Figure 4-13 Tower and desktop cases
11Measures and Properties of Electricity
- Successful PC technicians
- Understand electricity
- Know how to use electricity
- Know how to measure electricity
- Can protect computer equipment from electricity
- Units used to measure characteristics of
electricity - Volt, amp, ohm, and watt
12Table 4-2 Measures of electricity
13AC and DC
- Alternating current (AC)
- Oscillatory current driven by an alternating
voltage - Example house current oscillates at 60 Hz
- Direct current (DC)
- Single direction current driven by constant
voltage - Required by computer in small amounts, such as 5
V - Rectifier converts AC to DC
- Transformer changes ratio of current to voltage
- Power supply acts as a transformer and rectifier
14Figure 4-15 A transformer keeps power constant
but changes the ratio of current to voltage
15Hot, Neutral, and Ground
- Completing a circuit
- AC travels from power station to house on a hot
line - AC travels from panel to device using black (hot)
wire - AC flows out of device circuit in a white
(neutral) wire - AC returns to power station on a neutral line
- Short circuit failure due to excess flow of
electricity - Fuses protect circuits by melting wire (breaking
circuit) - Grounded neutral lines pass detoured AC to earth
- Lines in three-prong plugs hot, neutral, and
ground - Verify wiring of outlet for plug using a
receptacle tester
16Figure 4-16 Normally, electricity flows from hot
to neutral to make a closed circuit in the
controlled environment of an electrical device
such as a lamp
17Figure 4-18 Use a receptacle tester to verify
that hot, neutral, and ground are wired correctly
18Some Common Electric Components
- Materials used to make components
- Conductors weakly resist flow of current e.g.,
copper - Insulators highly resist flow of current e.g.,
ceramics - Semiconductors allow flow if charged e.g.,
silicon - Transistor
- Used to switch current on (1) and off (0)
- Also used to amplify current
- Made of three layers of semiconductor material
- Charge applied to center layer controls switching
19Figure 4-19 Symbols for some electronic
components and for ground
20Some Common Electric Components (continued)
- Capacitor
- Holds electrical charge for a period of time
- Used to create even flow of current in a PC
- Diode
- Allows electricity to flow in one direction only
- Used to rectify current (convert AC to DC)
- Resistor
- Controls the amount of current flowing through
device - Degree of resistance is measured in ohms
21Figure 4-20 Capacitors on a motherboard or other
circuit board often have embedded crossed lines
on top
22Protecting Your Computer System
- Electrical threats to a computer system
- Static electricity
- Electromagnetic interference
- Power surges
- Objectives in this section
- Understand nature of each threat
- Learn how to protect your system from these
threats
23Static Electricity
- Static electricity (electrostatic discharge or
ESD) - Due to charge difference between user and device
- Touching device causes discharge, damaging device
- ESD is particularly severe in dry and cold
climates - How to protect system from ESD
- Use ground bracelet or ESD gloves
- Touch computer case before touching components
- Safety rule unplug power cord before working in
case - Residual power in plugged device can cause damage
24EMI (Electromagnetic Interference)
- Caused by magnetic fields generated by current
flow - RFI (radio frequency interference)
- EMI in radio frequency range affecting reception
- The crosstalk problem
- Data in cables crossing EM fields gets corrupted
- Control crosstalk by shielding cables and power
supply - Use a tuned-down AM radio to detect EMI
- Other ways to protect a device from EMI
- Use line conditioners to filter out electrical
noise - Move the PC to a new location
25Surge Protection and Battery Backup
- Storms and uneven AC flow cause power surges
- Prevent power surges by installing an AC filter
- Types of devices used to manage power surges
- Surge suppressors
- Power conditioners
- Uninterruptible power supplies (UPSs)
- Use devices with UL (Underwriters Laboratory)
logo
26Surge Suppressors
- Also called a surge protector
- Protects equipment from sudden changes in power
- Works by absorbing and/or blocking the surge
- Recommended features
- Joules rating that is greater than 600 joules
- Protection activated in less than 2 nanoseconds
- Warranty for connected equipment and UL seal
- Light indicating that surge protection is working
- Data line protector for telephone line to modem
- Let-through voltage rating and line noise
filtering
27Figure 4-21 This surge suppressor has six
electrical outlets, two phone jacks, and a power
protection light
28Power Conditioners
- Sometimes called line conditioners
- Functions
- Protect against spikes or swells (voltage surges)
- Raise voltage during brownouts (voltage sags)
- Load supported measured in watts or volt-amps
(VA) - Determining the VA needed to support your system
- Multiply the amperage of each component by 120 V
- Add up the VA for each component
29Uninterruptible Power Supply
- UPS offers three benefits
- Conditions line to account for brownouts and
spikes - Provides power backup when AC fails (blackout)
- Provides protection against very high spikes
- Designs standby, inline, and line-interactive
- Smart (intelligent) UPS controlled with software
- What to consider when buying a UPS
- UPS rating should exceed VA load by at least 25
- Degree of line conditioning
- Warranties, guarantees, and service policies
30Energy Star Systems (The Green Star)
- Energy Star systems have the U.S. Green Star
- Indicates device meets energy conserving
standards - Devices computers, monitors, printers, copiers,
faxes - Goals of Energy Star (a.k.a. Green) standards
- Reduce overall electricity consumption
- Protect and preserve natural resources
- How computer components meet standards
- Uses standby program for switching to sleep mode
- No more than 30 watts used during sleep mode
31Power-Management Methods and Features
- Methods used to meet Energy Star standards
- Advanced Configuration and Power Interface (ACPI)
- Standard used by most desktops and notebooks
- Comprises four power-saving modes S1 - S4
- Some features controlled by BIOS, others by
Windows - Advanced Power Management (APM) specification
- AT Attachment (ATA) for various drives
- Display Power Management Signaling (DPMS)
32Figure 4-24 A power management BIOS setup screen
showing power-management features
33Energy Star Monitors
- Display Power Management Signaling (DPMS)
- Specifications applying to video card and monitor
- Allow both devices to simultaneously enter sleep
mode - Accessing energy settings in Windows 2000/XP
- Right-click the desktop and select Properties
- The Display Properties dialog box opens
- Click the Screen Saver tab
- If monitor is Energy Starcompliant, logo is at
bottom - Click Power button to open Power Options
Properties
34Figure 4-25 Changing power options in Windows XP
35Troubleshooting the Electrical System
- Problems can occur before or after boot
- Problems can be consistent or inconsistent
- Possible symptoms of an electrical problem
- The PC appears dead
- The PC sometimes halts during booting
- Error codes or beeps occur during booting
- You smell burnt parts or odors
- Check the simple things first
- Example determine whether all switches are on
36Problems with External Power
- Brownout (reduced current) may create issues
- Check out other devices using the same circuit
- Remove other devices to see if voltage increases
- Dealing with intermittent errors caused by noise
- Use a line monitor to monitor and condition
voltage
37Problems with Loose Internal Connections
- Can cause a system to appear dead or reboot
itself - Troubleshooting tasks
- Remove the cover of the case
- Check all power connections
- Check cables linking power supply to motherboard
- Check cables linking power supply to drives
38Figure 4-26 For an ATX or BTX power supply, the
remote switch wire must be connected to the
motherboard before power will come on
39Problems that Come and Go
- Intermittent symptoms indicating a post-boot
problem - The computer stops or hangs or reboots for no
reason - Memory errors appear intermittently
- Data is written incorrectly to the hard drive
- The keyboard stops working at odd times
- The motherboard fails or is damaged
- Power supply overheats and becomes hot to the
touch - The power supply fan becomes very noisy or stops
- Intermittent problems are often difficult to
solve
40Problems with an Inadequate Power Supply
- Power supply may not meet needs of new devices
- Testing for an adequate power supply
- Make all devices in the system work at the same
time - Example copy files from new drive to old drive
- Simple solution upgrade to a higher power supply
- Calculating total wattage needed by system
- Multiply volts in circuit by amps required for
device - Add all products to determine total wattage
- Power supply range 200 watts to 600 watts
41Problems with the Power Supply, Boards, or Drives
- Issues
- Inadequate or faulty power supply
- Components drawing power might be bad
- Problems caused
- System hangs or gives intermittent errors
- System reboots or does not boot at all
- Actions to take
- Isolate and remove any faulty expansion cards
- Upgrade or switch the power supply
- Test voltage output of power supply with a
multimeter
42Problems with the Power Supply Fan
- Defective fans usually hum before they stop
working - Response to diagnosis of defective fan
- Replace fan or the entire power supply
- If replacement does not work, suspect another
short - Do not operate a PC if the fan does not work
- Computers will overheat, damaging circuit boards
- Indirect sources of fan problems
- Shorts in drives, motherboard, or expansion cards
43Power Problems with the Motherboard
- Bad contact between board component and chassis
- Short can seriously damage the motherboard
- Check for missing or extra standoffs (spacers)
- Shorts in the circuit on the motherboard
- Look for damage to the bottom of the motherboard
- Look for burned-out capacitors
- Frayed wires on connections can also cause shorts
- Test hard drive cables connected to motherboard
44Problems with Overheating
- Causes intermittent problems
- May also cause the system to reboot or not boot
- Temperature in a case should not exceed 100 F
- Some possible solutions
- Remove dust from power supply, vents, heat sink
- Secure cables and cords with tie wraps
- Install another exhaust fan on the rear of the
case - Install a fan in expansion slot next to video
card - Replace component that is damaged
45Figure 4-27 Install one exhaust fan on the rear
of the case to help pull air through the case
46Replacing the Power Supply
- The power supply is a field replaceable unit
(FRU) - Criteria for replacement power supply to meet
- Uses the correct form factor
- Adequately rated for power in watts
- Has all power connectors needed by your system
- Before replacing power supply, test new device
- Connect components to new power supply
- Turn on PC and observe whether problem is solved
- If problem is solved, perform replacement
procedure
47Summary
- Form factor specifies size, shape, features of
device - Motherboard, power supply, and case share the
same form factor, such as ATX - Three types of cases desktop, tower, and
notebook - Quantities that characterize electricity
voltage, current, resistance, and power - Current flows from hot wires to neutral wires
excess current escapes through grounds
48Summary (continued)
- AC supplied by power station is transformed and
rectified before flowing into the PC - Major components in a circuit board transistor,
capacitor, diode, resistor - Electrical threats ESD, EMI, uneven current
flow, sudden power surges (or spikes) - Energy Star standards promote energy conservation
- PCs comply with Energy Star standards by enabling
devices to enter into a low power sleep mode