The Complete A+ Guideto PC Repair 5/e Update Chapter 4Disassembly and Power
Chapter Objectives After completing this chapter you will: • Describe how static electricity can damage a computer • Describe what type of equipment causes RFI and EMI and what to do when they occur • List tools a technician needs • Disassemble and reassemble a computer • Define and apply basic electronic terms • Perform basic checks, such as voltage and continuity • Describe the purposes of a power supply • Install a power supply and connect the motherboard and devices to it • Recognize the different power supply output voltages • Recognize different power connectors
Chapter Objectives (cont.) After completing this chapter you will: • Apply appropriate power saving techniques • Research and upgrade or replace a power supply • Solve power problems • Define and describe the purpose of different power protection devices • Describe what to do if an electrical fire occurs • Detail what to do when a computer component fails and must be thrown away • Detail alternatives for outdated computer • Describe good written communication techniques
Disassembly Overview • It 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 isn’t 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 Strap Disassembly – 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.
Disassembly • As with most tasks, the successful disassembly of a computer begins with preparation. • Do not remove the motherboard battery • Use proper grounding • Take notes • Have ample workspace • Do not stack adapters • Use anti-static bags if possible • Handle adapter/motherboard by edges • Handle hard drives carefully • Do not disassemble a CRT monitor or power supply
Tools • Having the proper tools to disassemble the computer can make the task easier and prevent damage to computer components. Medium flat-tipped screwdriver Small flat-tipped “tweaker” screwdriver #1 Phillips screwdriver #2 Phillips screwdriver Important Tools to Have ¼-inch nut driver 3/16-inch nut driver Small diagonal cutters Needlenose pliers
Reassembly • Reassembly iseasily 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. • Cables • Connectors
Cables and Connectors • Keyed – A connector or cable that has an extra metal piece that allows correct connections. Disassembly – Figure 4.4
Cables and Connectors • Pin 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 Cable’s Pin 1 Disassembly – Figure 4.2
Cables and Connectors • Solder 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 Connector Disassembly – Figure 4.5
Hard Drives • Hard 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 Maintenance • Preventive 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 Tips • LCD monitor cleaning • Use wipes specifically made for LCDs • Soft lint-free cloth dampened with water or a mixture of isopropyl alcohol and water • Don’t close laptop lid until screen is dry • Aerosol can disposal • Some states have special requirements • During preventive maintenance calls… • Check for system, driver, and anti-virus updates
Basic Electronics Overview • A technician should know a few basic electronic termsand 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 electricity • AC (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 computer’s power supply converts AC from the wall to DC for use by internal computer components.
Electronic Terms • Voltage – A measure of the pressure pushing electrons through a circuit. • Measured in volts • Power 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 Reading • Ensure the polarity (black to ground) is maintained when taking DC voltage readings.
Electronic Terms • Current –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 watts • Calculated by multiplying volts times amps. • Power supplies are described as providing a maximum number of watts.
Electronic Terms • Resistance –The amount of opposition to current in an electronic circuit. • Measured in ohms • A 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 Terms • The 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 Overview • The power supply is an essential component because none of the other components can function without it. • Converts AC to DC • Distributes lower voltage to computer components • Provides 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 computer • Linear (provides constant voltage)
Power Supply Form Factors • Power supplies have form factors (shapes and sizes) like motherboards do.Form factors today are the ATX, ATX12V v1.x, and ATX12V v2.x. • Specific models • LFX12V – low profile • SFX12V – small form factor • EPS12V – used with server motherboards and has an extra 8-pin connector • CFX12V – compact form factor • TFX12V – thin form factor • WFX12V – used with high-end workstations and some servers
Power Supply Tech Tips • Replace 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 Connectors • Good to have in the tool kit Y Connector Berg-to-Molex Converter Molex-to-SATA Converter
Purposes of a Power Supply • Purposes of the power supply • Convert 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.
Warnings WARNING! The power supply contains potentially lethal voltages and current! • To prevent injury, possible death, or damage to the computer • ALWAYS 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 manufacturer’s safety warnings and instructions for connecting the power supply or working inside the computer.
Power Tech Tips Powering on a power supply without anything attached could damage the power supply. An ATX power supply usually requires only a motherboard connection as a minimum load.
Front Panel Power Connectors Power –Figure 4.13
Power Supply ATX Connector Power – Figure 4.14
Power Supply Voltages • The 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 fans • PWR_OK feature
Power Supply Voltages • Occasionally voltages must be checked on a system. There are four basic power supply checks that can be accomplished: • Wall outlet AC voltage • DC voltages going to the motherboard • DC voltages going to a device • Ground with an outlet tester • A 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 Storage • When 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.
Laptop Power with Travel Configure for Hibernate rather than Standby Turn off wireless if possible De-Fragment the hard drivebefore leaving Avoid using USB devices Reduce screen brightness Avoid using DVD/CD drive. Keep battery contacts clean Avoid temperature extremes Avoid using multiple applications Seldom save documents— Turn off autosave
Laptop Overheating Locate air vents Elevate the laptop Keep them unblocked and clean. Do not place the computer on your lap to work. Pads, trays, and mats can be purchased with fans that are AC or USB-powered BIOS settings Check temperature settings for when the fans turn on. Check manufacturer web site Check for any fan/temperature monitoring gauges are available through BIOS or applications
Laptop Power • Laptops 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 Tips • Most laptops use Li-ion batteries. • These batteries last longer if they are kept cool. • 40% charged and place in refrigerator • Don’t power on after a temperature change • Allow to return to room temperature • Avoid 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 operation • CPU • Monitor • CD/DVD drive • Network adapter • Printer • Two common BIOS and adapter features that take advantage of ACPI • Wake 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 and Coming Out of Sleep Mode • Sometimes a computer will not come out of sleep mode and the power or reset button has to be pressed. • A screen saver conflicts with ACPI • Not all adapters or devices are ACPI-compliant • An adapter or device has an outdated driver • Keep the screen saver timeout value shorter than the power saver timeout value with energy efficient monitors.
ACPI and Not Going into Sleep Mode • Sometimes a computer will not go into sleep mode. • Determine if ACPI is enabled in the BIOS • Try disabling the antivirus application • Disable the screen saver to see if it is the problem • Determine if all drivers are ACP-compliant • Determine if power management is enabled through the operating system • Disconnect USB devices
Replacing or Upgrading a Power Supply • Its important to make sure that the power supply has enough power to run all the devices in the computer. • If you’re adding or upgrading devices, make sure you won’t 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 Supply • Dual 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)