Chapter 4Disassembly and PowerThe Complete A+ Guide to PC Repair 5/e Update

Chapter ObjectivesAfter completing this chapter you will:Describe how static electricity can damage a computerDescribe what type of equipment causes RFI and EMI and what to do when they occurList tools a technician needsDisassemble and reassemble a computerDefine and apply basic electronic termsPerform basic checks, such as voltage and continuityDescribe the purposes of a power supplyInstall a power supply and connect the motherboard and devices to itRecognize the different power supply output voltagesRecognize different power connectors

Chapter Objectives (cont.)After completing this chapter you will:Apply appropriate power saving techniquesResearch and upgrade or replace a power supplySolve power problemsDefine and describe the purpose of different power protection devicesDescribe what to do if an electrical fire occursDetail what to do when a computer component fails and must be thrown awayDetail alternatives for outdated computerDescribe good written communication techniques1-*

Disassembly OverviewIt is seldom necessary to completely disassemble a computer.Sometimes disassembly is accomplished to perform a preventive maintenance cleaning.Disassembly is also helpful in diagnosing problems of undetermined cause by removing components one by one or outside the case. Disassembly can also help with diagnosing grounding problems.Grounding Occurs when motherboard or adapter isnt properly installed and a trace (metal line on the motherboard or adapter) touches the computer frame and causes the adapter or other components to stop working.

Electrostatic Discharge (ESD)ESD (ElectroStatic Discharge) Occurs when stored up static electricity is discharged in an instantaneous surge of voltage. ESD damage is nonrecoverable and the most susceptible components are the CMOS and RAM chips.Anti-static Wrist Strap A strap connecting the technician to the computer and that equalizes the voltage potential between the two to prevent ESD. It is connected to a grounding post or a metal component such as the power supply. Electronic symbol for ground:

Warning: A technician should NEVER wear an ESD wrist strap when working inside a monitor because of high voltages!

Anti-Static Wrist StrapDisassembly Figure 4.1

EMI (Electromagnetic Interference)EMI (ElectroMagnetic Interference) Also called EMR (ElectroMagnetic Radiation) is noise caused by electrical devices. Can travel through electrical wires.RFI (Radio Frequency Interference) Noises that occur in the radio frequency range.Always replace the slot covers for expansion slots that are not being used. This will keep out dust and improve the airflow inside the computer.

DisassemblyAs with most tasks, the successful disassembly of a computer begins with preparation. Do not remove the motherboard batteryUse proper grounding Take notesHave ample workspaceDo not stack adaptersUse anti-static bags if possibleHandle adapter/motherboard by edgesHandle hard drives carefullyDo not disassemble a CRT monitor or power supply

ToolsHaving the proper tools to disassemble the computer can make the task easier and prevent damage to computer components. Important Tools to Have

ReassemblyReassembly is easily accomplished if the technician is careful and diagrams properly during disassembly. Exercise care and reinstall all components to their original location.Three major reassembly components Motherboards Have plastic connectors on the bottom called standoffs.Standoffs Plastic connectors on the bottom side of a motherboard that attach it to the case and prevent it from being in contact with the metal of the computer case.CablesConnectors

Cables and ConnectorsKeyed A connector or cable that has an extra metal piece that allows correct connections.Disassembly Figure 4.4

Cables and ConnectorsPin 1 Pin 1 on a cable should be connected to Pin 1 on the connector. The colored stripe on the edge of the cable identifies Pin 1 on the cable.Pin 1 on an adapter will be stenciled beside the connector.Ribbon Cables Pin 1Disassembly Figure 4.2

Cables and ConnectorsSolder Joints Solder connections on the back of motherboards and adapters. Pin 1 solder joints on the back of connectors are square.Pin 1 on a ConnectorDisassembly Figure 4.5

Hard DrivesHard drives must be handled carefully during disassembly because of the delicate nature of their very intricate construction.The read/write heads are located only millimeters from the platter storing all the data. A small jolt can cause them to make contact with the platter and cause permanent physical damage.Self-Parking Heads Read/write heads which pull away automatically when the computer powers off. This feature still would not prevent damaged caused by an accident or mishandling.

Preventive MaintenancePreventive Maintenance Certain procedures performed to prolong the life of the computer, such as cleaning the computer, drive heads, keyboard keys, printers, and monitor screen.MSDS (Material Safety Data Sheets) Sheets that contain information about a product, its toxicity, storage, and disposal.

Tech TipsLCD monitor cleaningUse wipes specifically made for LCDsSoft lint-free cloth dampened with water or a mixture of isopropyl alcohol and waterDont close laptop lid until screen is dryAerosol can disposalSome states have special requirementsDuring preventive maintenance callsCheck for system, driver, and anti-virus updates*

Basic Electronics OverviewA technician should know a few basic electronic terms and concepts when working with computers and testing components. Electricity (or power) - Electrons flowing through a conductor, just like water flows through a pipe. The two types of electricityAC (Alternating Current) Electricity where electrons flow in both directions and is provided by a wall outlet. Radios, toasters, and televisions are some devices that use AC power.DC (Direct Current) Electricity where the electrons flow in only one direction. Low voltage DC power is used by computer components, or anything with batteries. The computers power supply converts AC from the wall to DC for use by internal computer components.

Electronic TermsVoltage A measure of the pressure pushing electrons through a circuit. Measured in voltsPower supply output is measured in volts (DC) and are typically +3.3 volts, +5 volts, - 5 volts, +12 volts, and 12 volts. The + or refers to polarity which is simply the condition of being either positive or negative with respect to some voltage point, usually 0 volts, or ground.Capacitor A component that holds a charge even after the computer is turned off. CRT monitors have capacitors that can stay charged with high voltage for hours after being turned off. Measured in farads

DC Voltage ReadingEnsure the polarity (black to ground) is maintained when taking DC voltage readings.*

Electronic TermsCurrent The number of electrons going through a circuit every second. Measured in amps (amperes) Every device needs some current to operate and a power supply may be rated at the total amount of current it can supply at a certain voltage level, such as 20 amps at the 5-volt level, or 8 amps at the 12-volt level.Power How much electrical work is being done. Measured in wattsCalculated by multiplying volts times amps. Power supplies are described as providing a maximum number of watts.

Electronic TermsResistance The amount of opposition to current in an electronic circuit. Measured in ohmsA good cable or fuse will have very low resistance (close to zero).A broken wire or bad fuse will have very high resistance (millions of ohms, sometimes displayed as infinite).Continuity A connection from one end of a wire to another. Good continuity means little or no resistance. Bad continuity means high or infinite resistance, such as with a broken wire in a cable or a bad fuse. Continuity checks can also be used to determine which connector pins on one end of a cable are attached to what pins on the other connector end.

Electronic TermsThe sample meter readings in figure 4.7 demonstrate a good connection - good continuity or zero resistance, also known as a short, as well as a broken wire bad continuity or infinite resistance, also known as an open.Power Figure 4.7

Power Supply OverviewThe power supply is an essential component because none of the other components can function without it. Converts AC to DCDistributes lower voltage to computer componentsProvides cooling with its fan.It can be the source of strange and hard to diagnose problems and easily causes damage to other internal components.Two basic types of power supplies Switching (requires a load or something attached to it using current), which is the type used by a computerLinear (provides constant voltage)

Power Supply Form FactorsPower supplies have form factors (shapes and sizes) like motherboards do. Form factors today are the ATX, ATX12V v1.x, and ATX12V v2.x. Specific modelsLFX12V low profileSFX12V small form factorEPS12V used with server motherboards and has an extra 8-pin connectorCFX12V compact form factorTFX12V thin form factorWFX12V used with high-end workstations and some servers

Power Supply Form Factors

ATX Power Supply

ATX Power Supply Connectors

ATX Power Supply Connectors*

Power Supply Tech TipsReplace a bad power supply with one of equal or greater wattage.A rule of thumb is that if two power supplies are equal in wattage, the heavier one is better because it uses a bigger transformer, bigger heat sinks, and more quality components.Not all 24-pin motherboard connectors can accept the 20-pin power supply connector (older ATX power supply). Obtain a 24- to 20-pin adapter*

Power Converters and Y ConnectorsGood to have in the tool kit*Y ConnectorBerg-to-Molex ConverterMolex-to-SATA Converter

Purposes of a Power SupplyPurposes of the power supplyConvert AC wall outlet voltage to DC voltage.Create and distribute lower DC voltages to internal components throughout the computer.Provide cooling to the computer with its fan.

WarningsWARNING!The power supply contains potentially lethal voltages and current!To prevent injury, possible death, or damage to the computerALWAYS exercise extreme caution when working inside the computer if it is plugged into the wall outlet and/or the power supply is operating. UNPLUG the computer from AC power (power cable from wall outlet to the power supply) when working with wires (such as connecting the front panel power switch) or connecting/disconnecting internal power cables.ALWAYS follow ALL the manufacturers safety warnings and instructions for connecting the power supply or working inside the computer.

Tech TipsPowering on a power supply without anything attached could damage the power supply.PowerAn ATX power supply usually requires only a motherboard connection as a minimum load.

Front Panel Power ConnectorsPower Figure 4.13

Power Supply ATX ConnectorPower Figure 4.14

Power Supply VoltagesThe wires from the power supply carry the following levels of DC voltage:(+) 5 volts: motherboard, most adapters, CD/DVD and hard drive, some newer drive motors, some chips(-) 5 volts: seldom used(+) 12 volts: CD/DVD and hard drives (for internal motors)(-) 12 volts: seldom used(+) 3.3 volts: some chips on motherboards, including CPUs; also memory, PCI/PCIe adapters, and some laptop fansPWR_OK feature

Power Supply VoltagesOccasionally voltages must be checked on a system. There are four basic power supply checks that can be accomplished:Wall outlet AC voltageDC voltages going to the motherboardDC voltages going to a device Ground with an outlet testerA power supply tester be used to check DC power levels on the different connectors. Exercise extreme caution when checking AC voltages because voltages harmful to the technician are present!

Laptop Travel and StorageWhen traveling with a laptop:Remove all cards that insert into slots.Remove of media disks.Ensure that all drive doors and devices are securely latched.Check that the laptop is powered off or in hibernate mode.Carry laptop in a padded case. Never lay laptop upside down on conveyor belt. Never pick a laptop up by the display when the laptop is opened.1-*

Laptop Power with TravelReduce screen brightnessTurn off wireless if possibleAvoid using DVD/CD drive.Configure for Hibernate rather than StandbyKeep battery contacts cleanSeldom save documentsTurn off autosaveDe-Fragment the hard drive before leavingAvoid using multiple applicationsAvoid using USB devicesAvoid temperature extremes

Laptop Overheating*BIOS settingsCheck temperature settings for when the fans turn on.Check manufacturer web siteCheck for any fan/temperature monitoring gauges are available through BIOS or applications

Laptop PowerLaptops either use a battery (DC power) or an AC connection.On most models, the battery recharges when the laptop has AC power attached.Some power supplies and laptops have input voltage selectors.Others have the ability to accept input from 100 to 240 volts for use in various countries.*

Laptop TipsMost laptops use Li-ion batteries.These batteries last longer if they are kept cool. 40% charged and place in refrigeratorDont power on after a temperature changeAllow to return to room temperatureAvoid direct sunlight*

ACPI (Advanced Configuration and Power Interface)Allows the operating system, BIOS, and motherboard to have control over various devices power and modes of operationCPUMonitorCD/DVD driveNetwork adapterPrinterTwo common BIOS and adapter features that take advantage of ACPIWake on LAN allows a network administrator to control power to a workstation and come out of sleep mode for operating system, application, and anti-virus updates.Wake on Ring allows a computer to come out of sleep mode to receive phone calls, faxes, and e-mails.

ACPI Operating States*

Common BIOS Power Settings*

ACPI and Coming Out of Sleep ModeSometimes a computer will not come out of sleep mode and the power or reset button has to be pressed.A screen saver conflicts with ACPINot all adapters or devices are ACPI-compliantAn adapter or device has an outdated driverKeep the screen saver timeout value shorter than the power saver timeout value with energy efficient monitors.

ACPI and Not Going into Sleep ModeSometimes a computer will not go into sleep mode.Determine if ACPI is enabled in the BIOSTry disabling the antivirus applicationDisable the screen saver to see if it is the problemDetermine if all drivers are ACP-compliant Determine if power management is enabled through the operating systemDisconnect USB devices

Replacing or Upgrading a Power SupplyIts important to make sure that the power supply has enough power to run all the devices in the computer. If youre adding or upgrading devices, make sure you wont be exceeding the wattage rating for the power supply with the new configuration.If you upgrade or replace the power supply, make sure its power rating is high enough to meet the needs of the computer configuration and the power supply is the right size and form factor to fit the computer case.

Replacing or Upgrading a Power SupplyDual rail power supply has two +12V output lines, one used for the CPU.Triple rail power supply has three +12V output lines for devices.Multi-core processors and video cards use 12V power in addition to devices that have motors such as hard drives and CD/DVD drives.Ensure enough amperage is provided for all installed devices that use 12V power.An auto-switching power supply monitors incoming voltage and automatically switches itself accordingly. Commonly found in laptops (110 vs. 220)

Replacing or Upgrading a Power Supply

Sample Computer +12V Usage

Power Supply ProblemsYou should never take the power supply apart unless you have a background in electronics. Replace the entire power supply when it is faulty; power supplies are inexpensive.Power supply problems are usually easy to check. You should:Check to see that the power supply is plugged into the wall outlet and snugly into the power supply. Replace it to verify functionality.If the power supply has never worked before, check the 115/230 switch to be sure its in the 115 position.Ensure the power supply fan is turning. If not, check the wall outlet for proper AC voltages with an AC circuit tester.If a surge strip is used, make sure its powered on, then try another outlet in the strip, or another strip to verify functionality.

Symptoms of Power Supply ProblemsThe computers power light is off.The power supply fan does not turn with computer powered on.The computer sounds a continuous beep.When the computer powers on, it does not beep at all.When the computer powers on, it sounds repeating short beeps.During POST, a 02X or parity POST error code appears (where X is any number).The computer reboots without warning.The power supply fan is noisy.The power supply is too hot to touch.The monitor power light is on, but nothing appears. No PC power light is on.

Adverse Power ConditionsDo not create a trip hazard with a surge strip

Adverse Power ProtectionAlthough power supplies have built-in protection against adverse power conditions, the best protection for a computer during a power outage or thunderstorm is to unplug it.Three devices are commonly used to protect the power supply from adverse conditions. They are:A surge protectorA line conditionerAn Uninterruptible Power Supply (UPS)

Surge ProtectorsSurge protector Is commonly a six-outlet strip with built-in protection against overvoltage.MOV (Metal Oxide Varistor) An electronic component in most surge protectors that protects the computer or device that plugs into one of the outlets on the surge strip.Power Figure 4.17

Surge Protector Features

Line ConditionersLine Conditioners protect the computer from overvoltages, undervoltages, and adverse noise conditions over electrical lines.The line conditioner monitors AC electricity and adjusts the voltage being sent to the computer.

Uninterruptable Power Supply (UPS)UPS (Uninterruptable Power Supply) Provides power to a computer or device for a limited amount of time when there is a power outage. If the power from the wall outlet goes out, the battery continues to provide power for at least long enough to shut down the computer properly.Sine Wave Pattern for AC voltage in its correct form and what you want the UPS you choose to have for its output.Square Wave The AC voltage pattern described by cheaper, and thus less effective, UPS.

Uninterruptable Power Supply (UPS)Three things to look for when purchasing a UPS are to be sure that:There is sufficient battery time to protect all devices.The amount of current the UPS produces is sufficient to protect all devices.The output waveform is a sine wave.

Standby Power Supply (SPS)SPS (Standby Power Supply) Provides power to a computer only when it loses AC power.Does not provide protection against noise or over/under voltages.The SPS must detect a power-out condition first and then switch over to the battery. Because of this, switching time is very important. Any time under five milliseconds is acceptable.

Phone Line IsolatorPhone line isolator Also called a modem isolator, provides protection against phone line surges.Goes in between a modem and the wall jack to protect the computer against power surges on the phone line.Sometimes contained in a surge strip

Electrical FiresElectrical fires in computers are uncommon, but can still occur. If possible, unplug the computer if there is an electrical fire, but dont risk injury to do so.Type C Fire Extinguisher A type of extinguisher used only on electrical fires.Type A-B-C Fire Extinguisher A type of extinguisher used on either Type A (wood, paper, cloth), Type B (flammable liquids or gases), or Type C fires.

Computer Disposal/RecyclingComputers and electronic devices can contain materials which pose a threat to the environment such as: lead, cadmium, mercury, nickel, and zinc. Every state has regulations for disposing of electronic equipment.1-*

Alternatives to DisplosalDonate to schools and charitiesIf the operating system is not put on another system, leave on the donated computer and provide proof of purchase.Erase data stored on the donated computerRecycle outdated electronicsMany companies accept old parts and can reuse themBuy electronics designed with saving resources in mind and that are energy efficient.Check with the computer/component manufacturer to see if they have a recycling program.*

Written Communication SkillsTechnicians use written skills when documenting problems and writing emails. Documentation can include a basic description of what was done, and time spent on the job. It should be written in a manner as to be helpful to other technicians.Suggested guidelines for effective emails include using a spelling and grammar checker, and using proper capitalization, never only uppercase or lowercase letters. 1-*

Effective EmailDont use email when a meeting or phone call is more appropriateInclude a subject in the email subject lineDo not write an email when angrySend email only to the appropriate peopleStick to the point of the email; do not be wordyUse a spell/grammar checkerUse proper grammar, capitalization, punctuation, and spelling. Do use all uppercase or lowercase letters.Write each email as if it were being posted to a billboard.

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Older hard drives had utility programs to park, or lock, the heads in place away from the platters when not in use.

*** -Wall outlet voltage is normally 120 VAC (or volts AC).*****Older power supplies are the PC/XT, AT, AT/Tower,and Baby AT. The other form factors are the LPX, and SFX. ***********To keep battery contacts clean, dab of rubbing alcohol on a lint free swab.*- APM, ACPI, and many of their features are defined on the following slides -

***-You can determine the number of watts the computer devices are using by multiplying the amps used for each device by the voltage level theyre operating at. -Example: (+)5 volts x 5 amps = 25 watts- If you exceed wattage rating for the power supply, it may mean the computer will have power problems and/or youll have to upgrade the power supply.*******These devices are described in the following slides.

*Surge protector is also known as a surge strip or surge suppressor, **- Line Conditioners are also called power conditioners. - Be careful not to plug too many devices into a line conditioner because you may overload it.

*UPS - The UPS has a battery inside that charges all the time and provides power to the computer through an inverter. **- Although it has a battery like a UPS, the SPS doesnt provide constant power to the computer, but only when the computer loses AC power.

*- Many surge protectors now have a modem isolator built-in.

* A technician should be aware of what to do in the event of an electrical fire and what type of fire extinguisher to use. Follow the manufacturers instructions on the best way to use a fire extinguisher.

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