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- Electricity and Power Supplies
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- How electricity is measured
- How to protect your computer system from damaging changes in electrical
power
- About types of form factors and computer cases
- How to detect and correct power supply problems
- About Energy Start specifications
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- Direct relationship
- As electrical potential difference (or voltage) increases, electrical
current increases
- As voltage decreases, current decreases
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- Voltage and current have a direct relationship
- When voltage increases, current increases
- Resistance has an inverse relationship with voltage and current
- As resistance increases, either current or voltage decreases
- As resistance decreases, either current or voltage increases (Ohm’s
Law)
- One volt drives a current of one amp through a resistance of one ohm
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- Cycles or oscillates back and forth rather than traveling in one
direction
- 60 times in one second (60 hertz)
- Most economical way to transmit electricity to homes and workplaces
- Can be forced to travel great distances by decreasing current and
increasing voltage
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- Travels in only one direction
- Required by most electronic devices, including a computer (power supply
acts as both a rectifier and a transformer)
- Rectifier converts AC to DC
- Transformer
- Changes the ratio of current to voltage
- Overall power stays constant
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- Short circuit occurs when electricity is allowed to flow uncontrolled
from hot line to neutral line or from hot line to the ground
- Fuses prevent too much current from flowing through the circuit
- Neutral line to a house is grounded many times along the way and at
breaker box
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- Transistors
- Capacitors
- Diodes
- Ground
- Resistors
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- Conductors
- Insulators
- Semiconductors
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- Electronic device that can serve as a gate or switch for an electrical
signal
- Can amplify flow of electricity
- Made of three layers of semiconductor material
- Basic building block of an integrated circuit (IC) that is used to build
a microchip
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- Can hold an electrical charge
- Smoothes out uneven flow of electricity through a circuit
- Maintains a charge long after current is no longer present
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- Diode
- Semiconductor device that allows electricity to flow in only one
direction
- Resistor
- Electronic device that limits amount of current that can flow through
it
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- Make notes so you can backtrack
- Remove packing tape and cellophane 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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- Don’t touch chips on motherboard or expansion cards
- Don’t touch a chip with a magnetized screwdriver
- Don’t use a graphite pencil to change DIP switch settings
- Turn off a computer before moving it
- Keep disks away from magnetic fields, heat, and extreme cold
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- Turn off power and unplug computer
- 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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- Electrostatic discharge (ESD)
- Electrical charge at rest
- Brief flow of electricity caused by contact between two objects that
had a difference in voltage potential
- Can cause catastrophic or upset failure
- Static control devices or methods:
- Ground bracelet or static strap (except when working inside a monitor
or with high-voltage equipment)
- Ground mats
- Static shielding bags
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- Caused by the magnetic field produced as a side effect when electricity
flows
- Radio frequency interference (RFI) can cause problems with radio and TV
reception
- Use a line conditioner to filter electrical noise causing the EMI
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- Devices that control electricity to a computer
- Surge suppressors (surge protectors)
- Power conditioners
- Uninterruptible power supplies (UPSs)
- Should have UL (Underwriters Laboratory) logo
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- Protect equipment against sudden changes in level of power
- Shunt type, series type, or combination
- Can come as power strips, wall-mounted units that plug into AC outlets,
or consoles; some provide RJ-11 telephone jack to protect modems and fax
machines
- Data line protector (for phone line)
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- Provide protection against spikes
- Regulate (condition) the power, providing continuous voltage during
brownouts
- Sometimes called line conditioners
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- Benefits
- Conditions line for brownouts and spikes
- Provides backup power during a blackout
- Protects against very high potentially damaging spikes
- Types
- Standby device
- Inline device
- Line-interactive device
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- Intelligent UPS
- Can be controlled and managed from utility software at a remote
computer
- Must have a serial port connection to PC and a microprocessor on board
- What to consider when buying a UPS
- Cost
- UPS rating should exceed total VA or wattage output by at least 25%
- Be aware of degree of line conditioning
- Consider warranty, service policies, and guarantee
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- Form factor
- Description of size, shape, and general makeup of a hardware component
- Use same form factor for motherboard, case, and power supply
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- XT (older, outdated)
- AT
- ATX (most popular)
- LPX
- NLX
- Backplane systems
- Most common form factors used on PCs:
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- Used on older motherboards
- Uses full-size AT cases used by original IBM AT personal computer
- Cannot be used with smaller AT cases or with newer ATX cases
- Difficult to install, service, and upgrade
- No longer produced by most manufacturers
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- Industry standard from 1993-1997 because of greater flexibility
- Power supplies blow air out of computer case
- Smaller motherboards fit into many types of cases
- Problematic position of CPU in relation to expansion slots not resolved
- Cables might not be long enough
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- Superseded earlier AT and Baby AT form factors
- Open, nonproprietary industry specification developed by Intel in 1995
- Easier to add and remove components
- Greater support for I/O devices and processor technology
- Lower costs
- Better positioning of components on motherboard
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- Possible to reduce cable lengths, which can help reduce potential for
EMI and corrupted data
- Power supply and motherboard use single power connector (P1 connector)
- Power supply fan blows air into case; cools processor directly
- Soft switch feature
- Other types of ATX boards (Mini-ATX, MicroATX, FlexATX )
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- Developed by Western Digital
- Often used in low-cost systems
- Expansion cards mounted on riser card that plugs into motherboard
- Not easy to upgrade
- Cannot handle physical size of recently developed processors
- Not designed to handle higher temperature at which faster processors
operate
- Use low profile cases and slim-line cases
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- For low-end PC motherboards
- Use low-profile cases
- Provide greater support for current and up-and-coming processor
technologies
- Flexible; use space efficiently
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- Do not use a true motherboard, but a board that normally sits against
back of a proprietary case that has slots for other cards
- Active backplanes
- Passive backplanes
- Not generally used in PCs
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- Computer case (chassis)
- Houses power supply, motherboard, expansion cards, drives
- Lights and switches on front panel for controlling and monitoring PC
- Needs to fit its intended use
- Major categories
- Desktop cases
- Tower cases
- Notebook cases
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- Classic case with four drive bays and six expansion slots; sits on
desktop and does double duty as a monitor stand
- Being replaced by smaller and more space-efficient cases
- For low-end desktop systems, compact cases follow either the NLX, LPX,
or Mini-LPX form factor
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- Provide maximum space for working inside a computer and moving
components around
- Variations
- Minitower
- Midsize tower (most popular)
- Full-size tower
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- Used for portable computers that have all components of a desktop
computer
- Weigh between six and eight pounds
- Can present difficulties in expansion
- Designed to conserve space, allow portability, use less power, and
produce less heat
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- Measuring voltage of a power supply
- How to upgrade and install power supplies
- Troubleshooting power system and power supply
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- Use a multimeter
- Before using, tell it three things
- Whether to measure voltage, current, or resistance
- Whether the current is AC or DC
- What range of values it should expect
- How to measure voltage
- How to measure current
- How to measure continuity
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- 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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- 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 the user
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- Any burnt parts or odors?
- Everything connected and turned on? Loose cable connections? Computer
plugged in?
- All switches turned on—computer, monitor, surge protector, UPS, separate
circuit breaker? Wall outlet good?
- If fan is not running, turn off computer: Connections to power supply
secure? All cards securely seated?
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- Check for correct wire connections to the motherboard
- Remove all nonessential expansion cards one at a time
- Vacuum entire unit
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- Troubleshooting the power supply itself
- Troubleshooting the power supply fan
- Power problems with the motherboard
- Overheating
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- Satisfy energy-conserving standards of the U.S. EPA
- Generally have a standby program that switches the device to sleep mode
when it is not in use
- Apply to computers, monitors, printers, copiers, and fax machines
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- 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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- Green timer on the motherboard
- Doze time
- Standby time
- Suspend time
- Hard drive standby time
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- Most adhere to DPMS specifications which allow video card and monitor to
go into sleep mode simultaneously
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- Basic understanding of electricity
- How to measure electricity
- Form in which electricity comes to you as house current
- Power supply, backup power sources, how to measure power supply output,
and how to change a defective power supply
- Introduction to form factors
- How Energy Star devices save energy
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