COMPUTER HARDWARE (Part 5a) Power Supplies

Overview - Explain the basics of electricity • In this chapter, you will learn to - Explain the basics of electricity - Describe the details about powering the PC - Install, maintain, and troubleshoot power supplies

Understanding Electricity

Measuring Electricity • Voltage—pressure of electrons in a wire - Unit of measurement: Volts (V) • Current— flow (or amount) of electrons in a wire - Unit of measurement: Ampere (A) - When voltage is applied to a wire, electrons flow, producing current • Wattage—measure of power consumed or needed - Unit of measurement: Watt (W) W = V * A • Resistance—impedance or opposition to the flow - Unit of measurement: Ohm (Ω)

Measuring Electricity • Wire has amperage rating - Defines how much amperage it can handle • i.e., 20 amp, 30 amp - If you exceed amperage • Wires heat up—may break • Circuit breakers are heat sensitive - Sense when amperage exceeds threshold - Breaks the circuit to stop the flow of electricity

Two Types of Current - Electricity provided at wall socket • Alternating Current (AC)—electrical current flows in both directions - Electricity provided at wall socket - Frequency of alternations measured in cycles per second, or hertz (Hz) • Direct Current (DC)—electrical current flows in one direction - Electricity provided by batteries

Powering the PC : Types of Power • PCs use DC voltage • Power companies supply AC voltage • The power supply in a computer converts high-voltage AC to low-voltage DC

Supplying AC • In the U.S., 115 VAC is standard • Other countries use 230 VAC - Many PCs may have a small switch on the back to choose 115 or 230 V (used in other countries) - Pay attention to this switch, especially when traveling overseas

Outlet Voltages - Hot has 115 V - Neutral carries no voltage • Hot and neutral provide path for AC - Hot has 115 V - Neutral carries no voltage • Ground used for safety - Returns excess electricity to ground Wall outlet

Multimeter Basics - Voltage - Resistance - Continuity • A multimeter (or Volt-Ohm meter: VOM) measures: - Voltage - Resistance - Continuity • Warning - Set it properly before measuring - If not, damage can occur

Testing AC Voltage - Hot should be 115 VAC • Verifies wiring of outlet - Hot should be 115 VAC - Neutral completes the circuit - Ground should go to ground

Surge Suppressors • Surge suppressors provide protection against power surges • Insert between the power supply and the outlet • Joule is a unit of electrical energy - Surge suppressor rated by joules - Higher joules = better protection • Some protect more than AC surges - Phone lines for traditional modems - Cable connections for cable modems

Uninterruptible Power Supply • An uninterruptible power supply (UPS) provides protection against a power dip or power outage - Contains a battery that provides continuous AC power - Provides surge protection and power conditioning • Constantly charges battery - All UPSs measured in watts and volts-amps

Supplying DC - Converting AC into 5, 12, and 3.3 V DC • The power supply acts as a step-down transformer - Converting AC into 5, 12, and 3.3 V DC - PCs use a 12 V current to power motors on devices such as hard drives and CD-ROM drives - PCs use a 5-volt/3.3-volt current to support onboard electronics

Power Connectors Original PC Main 4-pin Peripheral Floppy Drive Power Cable Power Cable Power Cable 20-pin ATX Main 24-pin ATX Main 20+4-pin ATX Main Power Cable Power Cable Power Cable

Power Connectors 6-pin Auxiliary SATA 4-pin ATX +12V Power Cable 8-pin EPS +12V 4+4-pin +12V Power Cable Power Cable

Power Connectors 6-pin PCI Express 8-pin PCI Express Power Cable Power Cable Power Cable

Power Connectors - Can plug in only one way • Connectors are keyed - Can plug in only one way • Splitters and adapters - Can create two power connectors from one - Can convert Molex to SATA

Soft Power CMOS - P1 power connector • ATX power supplies first to use - P1 power connector • Always on when plugged in - 5 V supplied to motherboard when plugged in • Configured in CMOS

Power Supply Versions Version Year of Introduction Included Power Cable Connectors PC 1981 Original PC Main 4-pin Peripheral ATX 1995 20-pin Main 4-pin Peripheral Floppy Drive ATX 12V 1.0 2000 20-pin Main 4-pin ATX +12V 4-pin Peripheral Floppy Drive 6-pin Auxiliary ATX 12V 1.3 2003 20-pin Main 4-pin ATX +12V 4-pin Peripheral Floppy Drive 6-pin Auxiliary SATA

Power Supply Versions Version Year of Introduction Included Power Cable Connectors ATX 12V 2.0 2003 24-pin Main 4-pin ATX +12V 4-pin Peripheral Floppy Drive 6-pin PCI Express SATA EPS 12V 2003 24-pin Main 8-pin EPS +12V 4-pin Peripheral Floppy Drive 6-pin PCI Express SATA PCI Express 2.0 2007 24-pin Main 4-pin ATX +12V 8-pin EPS +12V 4-pin Peripheral Floppy Drive 6-pin PCI Express 8-pin PCI Express SATA

Original PC Power Cables • Introduced in 1981 • Plugged in side-by side, either black to black or sparks to smoked • Standard 5V and 12V supplies • Maximum power usage 65 watt

4-pin Peripheral Power Cables • Introduced during the introduction of the first original PC • Used for HDDs and other add-ons such as fans, extra video card power, supplemental motherboard power, and case lighting • Still popular until today but reducing due to the introduction of SATA

Floppy Drive Power Cables • Introduced for the 3.5 inch floppy disks • Sometimes used as an auxiliary power cable for AGP video cards • Small connector and 20 awg wires, limited to low current use

ATX 20-pin Main Power Cable • Introduced in 1995 featuring new standards ATX • Additional 3.3V power supply for newer chips • Ability to switch on and off without using power switch • Increase maximum power to 250 Watt

ATX 24-pin Main Power Cable • Introduced in 2000 to increase power lines • Extension for enhanced PCI Express use • Ability to work on 20-pin ATX boards • Increase maximum power to 350~450 Watt

EPS 12V Main Power Cable • Introduced in 2003 originally designed for workstations • Enhanced 12V features to support multiple CPUs • Maximum power to 380~450 Watt

ATX12V or P4 Connector - Provides more 12 V power - Can be Molex • Many motherboards require a second, four-wire connector - Provides more 12 V power - Can be Molex - Can be PCI-E

IT Technician Niche Market Power Supply Form Factors

Form Factors - TFX12V, SFX12V, CFX12V, LFX12V • Niche market power supply form factors - TFX12V, SFX12V, CFX12V, LFX12V • Active PFC - Power Factor Correction - Common in quality power supplies - Eliminates harmonics

Wattage Requirements • Every device requires some wattage - Often starting requirements are higher than running requirements • Power supplies don’t run at 100% efficiency - ATX 12 V requires power supplies to be at least 70% efficient • General recommendation - Use at least a 400 W power supply - Enough extra for starting and future growth

Installing, Maintaining, and Troubleshooting Power Supplies

Installing - Disconnect wires - Remove 4 standard screws - Remove PS • Removing - Disconnect wires - Remove 4 standard screws - Remove PS • To install - Place PS in case - Replace screws - Connect wires

ATX Soft Power and CMOS Some ATX power supplies provide a • An ATX power supply never turns off real on/off switch on the back - Continues to supply 5V to the motherboard as long as it is connected to the power outlet • Always unplug an ATX power supply before working on it Can use a screwdriver or car keys to short the two power jumpers to turn the system on or off in special circumstances

Cooling • The power supply fan provides basic cooling for the PC - Fan keeps the voltage regulators cool and provides a constant flow of cool air through the computer - If power supply fan stops, replace power supply - Many fans have sensors to detect when they should run quicker

Cooling - Most modern computers have case fans • Case fan provides extra cooling for PC - Most modern computers have case fans - Often plug into Molex connector - Connector adapters can be used

Maintaining Airflow - Keep covers on case • Keep case closed - Keep covers on case - If an expansion card is removed from the PC, be sure to cover the hole with - Without proper airflow, the CPU can overheat and destroy itself

Reducing Fan Noise - Manually adjustable with knob • Some fans can be adjusted - Manually adjustable with knob - Software adjustable by sensing heat • Larger fans that spin slower are quieter • Higher-end fans are quieter - Use better bearings

CMOS Fan Options - Doesn’t control fans • Can monitor PC’s health by showing temperatures - Doesn’t control fans - Can set fan thresholds for alarms

Freeware Tool - Allows monitoring of fan speeds - Can set fan speeds • Speedfan - Allows monitoring of fan speeds - Can set fan speeds - Hundreds of chipsets supported

- Sudden death - Slowly over time When Power Supplies Die • Power supplies fail in two ways: - Sudden death • When the fan doesn’t turn and no voltage is present • Computer simply stops working - Slowly over time • Intermittent errors • Output voltages may exceed specs (± 10%)

Power Supply Test • Put the black lead onto any black wire connection • Put the red lead onto colored wire • 12 V ± 10% - 10.8 to 13.2 V • 5V ± 10% - If readings are outside tolerance and symptoms - 4.5 to 5.5 V • 3.3 V ± 10% exist, replace power supply - 2.97 to 3.63 V

Power Supply Test - Plug into motherboard - Plug into tester • Power supplies need a load - Plug into motherboard - Plug into tester • Check power switches - If faulty, can turn on with motherboard jumper

power supply When Power Supplies Die Slowly • Intermittent problems - Sometimes occur, sometimes don’t - You could measure voltage now and it’s good; 10 minutes later, system crashes • A dying power supply can cause - Random lockups and reboots - Sporadic boot-up difficulties • When you encounter intermittent symptoms, consider replacing the power supply

Fuses and Fire - Sense when amperage exceeds threshold • Circuit breakers are heat-sensitive - Sense when amperage exceeds threshold - Breaks the circuit to stop flow of electricity • Fuses blow for a reason - Power supply is malfunctioning - As a designed safety precaution, fuses blow (break) to stop circuit • Alternative is a possible fire

Fire Extinguishers - Ordinary combustibles such as paper and wood • Class A - Ordinary combustibles such as paper and wood • Class B - Flammable liquids such as gasoline • Class C - Live electrical equipment • Use only Class C extinguishers on electrical fires

Beyond A+ - Fancy colors, light up, and have extra fans • It glows - Fancy colors, light up, and have extra fans • Module power supplies - Reduced cables • Rail power - Look for power supplies that offer 16 to 18 A per 12 V rail