Exercise 1 Computer Hardware

Exercise 1

Computer Hardware#Welcome to Exercise 1. Today you will begin your examination of the computer hardware and learn the proper method of taking the personal computer apart. Lets begin by taking a look at the objectives of this exercise.#Objectives for Exercise 1When you complete this exercise, you will be able to:#The objectives are very important because they give you a concrete way of knowing if you learned what you should have learned. The objectives will generally be stated in this form: When you complete this exercise you will be able to...#Identify, disconnect, and reconnect the computers cables and cover.Identify the external connectors on a typical personal computer.Identify and explain the purpose of the major internal components.#Read over the objectives carefully and refer to them frequently as you complete the exercise. These same objectives are listed at the front of Exercise 1 in your workbook. Some of them may be covered in your reading assignment. When you have completed this lesson, you should double check to make sure you can perform each of them.#Why Disassemble the Computer?To upgrade.To repair.To add to it.#In the hands-on part of the exercise, you will partially disassemble the computer. You may be wondering: Why would I want to disassemble a computer in the first place? There are several reasons why you will have to do some level of disassembly. Perhaps the most frequent reason is to upgrade. Computer technology changes very quickly. That state-of-the-art computer you buy today may be out of date in a year and obsolete in two, unless it is upgraded. The best way to extend its useful life is to upgrade it frequently. This may include adding more memory, changing to a larger hard drive, or going to a faster modem. Another reason for disassembly is repair. Computers break. A hardware malfunction inside the computer requires some level of disassembly. Finally, you will have to do some disassembly to add a new capability such as a sound card, a CD-ROM drive, a modem, or a network card. In this exercise you will partially disassemble the computer so that you can become familiar and comfortable with the hardware and the procedures involved. #The three most important things to remember when disassembling a computer are:DocumentDocumentDocument!#The most important thing to remember when disassembling a computer is to document everything. It is embarrassing and sometimes costly to forget how everything goes back together. Your chances of getting everything back together properly increase dramatically when you have clear, detailed documentation.#DocumentWhere cards are located.How cables are routed.Orientation of cables and connectors.Hardware used to secure each component.Anything else that might cause confusion when reassembling.#In particular, you should document where the various cards inside the computer are located; how the cables are routed and oriented; the hardware used; and anything else that might cause confusion when you start putting things back together.#Your greatest enemy when working inside the computer is Electrostatic Discharge or ESD.

#Lets spend a moment talking about electrostatic discharge or ESD. When working inside the computer, more damage is done by electrostatic discharge than by any other single factor. In fact, any time the computer is open, you risk damaging the circuits inside by electrostatic discharge. Thats the bad news. The good news is this risk can be almost totally eliminated by a few common sense precautions.#Your best defense against ESD is the anti-static wrist strap.

#Your first line of defense is the anti-static wrist strap. It is a simple conductive strap. One end fits around your wrist; the other is clipped to ground on the computer. It will drain off any electrical charge that attempts to accumulate. It keeps your body and the computer chassis at the same potential, virtually eliminating the risk of ESD.#

An internal resistor providesshock protection.9#If you are concerned about deliberately grounding your body when working around electronics, set your mind at ease. A resistor built into the wrist strap limits the current to a safe level should you inadvertently brush against a live terminal.#Switch off power at the computer and at the workbench...#While the anti-static wrist strap greatly reduces the risk of ESD damage, there are some other precautions that should also be taken. Obviously, you should turn off power to the computer and those devices connected to it before you disconnect anything from the computer.#...but leave the computer plugged in. #However, it is a good idea to leave the computer plugged in. The reason for this is that the ground-wire on the line cord will keep the chassis at ground potential.#Use anti-static mats on the workbench and floor.#Also, it is good practice to use anti-static mats on your workbench and on the floor where you will be standing. These are conductive mats that, when properly grounded, prevent the build-up of static electricity.#Hold Circuit Boards by their Edges.#Circuit boards are especially vulnerable when they are unplugged from the computer. You should be very careful to handle the boards only by their edges. Avoid touching the components, the foil patterns, and the connectors on the board.#Store Circuit Boards in Anti-static Bags.#When not in use, boards should be kept in conductive anti-static bags. These simple precautions will go a long way toward eliminating the danger of ESD damage.#Tips for Disassembly.#Now, lets look at a few tips for disassembling the computer.#Turn off power to the computer and everything connected to it.#The first step is to turn off power to the computer and to anything else that is connected to it, such as the monitor and printer. Never connect or disconnect cables from live equipment.#Disconnect the monitor and set it aside.

#Once power is removed, disconnect the external cables. Disconnect the monitor and set it aside. The monitor is connected to the so-called VGA connector on the computer. Once disconnected, you can recognize the VGA connector by its fifteen pins, arranged in three rows of five pins each.#Disconnect the keyboard and set it aside.#Disconnect the keyboard and set it aside. Some keyboards use a large, round 5-pin connector called a DIN plug. #1010110101PS/2 Keyboard Connection#Others use a smaller, round 6-pin connector called a PS/2 type connector.#Disconnect the mouse and set it aside.#Disconnect the mouse and set it aside. Many computers use a serial mouse that connects to the COM1 serial port. In this case, the connector is a 9-pin D-shaped affair with the male end connected to the mouse. #1010110101PS/2 Mouse Connection#Others use the small, round 6-pin PS/2 type connector.#Remove these screws...22#Once everything is disconnected, you are ready to remove the cover. On this computer, the cover is held in place by four screws that are accessible from the back of the unit. Look for the four screws along the narrow lip of the cover where it overlaps the back of the computer, indicated here by the arrows. If the computer has a one-piece cover, you need to remove all four screws. If the computer has side panels, then you only have to remove the screws for one side. Looking at the back, that would be the right-side panel.#... not these.23#Be very careful that you do not take these screws out by mistake. These hold the heavy power supply in place, as you will see later from inside the computer.#1.2.24#Once the cover screws are removed, lifting the cover off is a two-step procedure. First slide the cover straight back a few inches. Then tilt the back of the cover up and lift it off as shown here. #Spreading the sides of the cover will help it to clear the computer.#Spreading the sides of the cover makes it easier to lift it off the computer. Dont overdo the spreading. Flex the cover just enough to clear the sides of the computer.#26132Removing the side panel.#If your computer uses side panels, you only have to remove the side shown here. Once the two panel screws are removed, slide the panel straight back a about an inch. Then, tilt the top of the panel out. Finally, lift it off. #27

#With the cover off, the inside of the computer looks something like this. There are five main items that are of immediate concern.#

The Motherboard.#The large board that occupies the lower left quarter of the chassis is called the motherboard. This single board contains the microprocessor, the various buses, and the interface circuitry. It also provides bus slots and sockets for a wide range of expansion boards.#The Motherboard may also be known as the:System BoardPlanar BoardBaseboardMain BoardLogic Board#The motherboard may be called a variety of names. Throughout its history, it has been variously called the system board, the planar board, the baseboard, the main board, and the logic board. In this course, we will call it the motherboard.#

The Power Supply.#Another very prominent item that is easy to find in any computer is the Power Supply. It is usually a metal cage with AC outlets accessible through the chassis on one side and a bundle of colorful cables on the other. The Power Supply converts the AC line voltage into low level DC voltages used by the various components inside the computer. #Standard Power Supply

#This is a standard computer power supply. One end plugs into the wall outlet, where 120 volt alternating current (VAC) is provided, and the other end provides low-voltage direct current. The connector on the bottom is used for a standard three-wire line cord. The top connector uses a special line cord that is designed for your monitorthis allows you to power your system with only one line outlet.Unless you have an electronics degree, a technician never opens the power supply. Consider it a replaceable, unrepairable module. The fans in common power supplies can fail, and when they do you replace the entire supply. Power supplies are cheap, and the circuits inside are dangerous.#Power Selection Switch

#Most power supplies have a switch on the rear panel. This switch allows the system to be used with the two different AC line voltages. In North America, the switch should always be in the 115 position. Some supplies call it 110, some 120. They all mean the same thing. The 230 position is used in other parts of the world. This setting normally requires a different type of line cord. #WARNING!Hazardous voltages contained within this power supply, not user serviceable. Return to service center for repair.#Pay attention to this warning, which is on nearly every power supply ever built. There are hazardous voltages present, even when the supply is not attached to the wall outlet. The circuits inside a power supply can store dangerous charges, which are hazardous if not handled properly. Dont open the power supply case. #Power Supply Connectors

#There are many colored cables coming out of the power supply. They connect to the motherboard and the drives. Sometimes the CPU fan is connected to one of these cables, and other internal peripherals may be attached as well. #Power Supply Output VoltagesAT-Type+5 Volts+12 Volts12 Volts5 Volts#Two types of PC power supplies are common today. With the so called AT type, the output voltages produced by the power supply are +5 Volts DC, +12 Volts DC, 12 Volts DC, and 5 Volts DC. #

Motherboard Power ConnectorsBlackWiresP9P8#The connectors from the AT-type power supply to the motherboard most often take this form. There are two connectors, usually labeled P8 and P9. They plug into a single jack on the motherboard. Unfortunately, they can be connected incorrectly. The correct connection is with the black leads side by side in the middle as shown here. Another way to remember the correct connection is that P9 should always be closest to the edge of the board.

#Power Supply Output VoltagesATX-Type+5 Volts+12 Volts12 Volts5 Volts+3.3 Volts#Another common type PC power supply is the ATX type. With the ATX type PC, the output voltages of the power supply are +5 Volts DC, +12 Volts DC, 12 Volts DC, 5 Volts DC and +3.3 Volts DC. #ATX Power Connector

#The power connection to the motherboard is also simplified by using a single 20-pin connector rather than the two 6-pin connectors required by the AT-type board. Because the supplied voltages and connectors are different, the AT and ATX power supplies are not interchangeable.

#

ATX Power Connector#The ATX motherboard has a single 20-pin power connector. If you look closely, you will notice that this connector will not allow the cable to be attached incorrectly.

#Second P4 Motherboard Power Connector Supplies 12 Volts40#With the ATX style motherboard that supports the Pentium 4 processor, power is supplied to two separate locations. Main power still comes from the 20-pin connector I just described. A second 4-pin power connector supplies two additional 12-volt lines to support increased current demands of the CPU.#Large Molex Connector

#All PC power supplies distribute voltages to the various drives and fans using two types of connectors. The four-pin Molex connector and its socket are shown here. This type of connector is often used to supply power to hard disk drives, CD-ROM drives, and some older 5-inch floppy disk drives. Sometimes you will find one or two extra Molex connectors coming out of the power supply. These are for future expansion. The Molex connector is keyed so that it can only be connected in one direction. #Berg Connector

#Another type of power connector is the four-pin Berg connector. It is normally used to provide power to the 3-inch floppy disk drive. #

Some connectors are held in place with a latch.#A necessary step in disassembling the computer is to unplug these various power connectors. Care should be taken when doing this. First determine whether or not there is a latch holding the connector in place. If so, you must lift the latch before attempting to wiggle the connector loose.#Grasp the connector by the shell

Never by the leads.44#Second, grasp the connector by the plastic shell. Wiggle it up and down and end to end while pulling slightly on the shell. Never pull the wire leads.#

The CD-ROM Drive#Now, lets look at some of the other components in the computer. Most computers have a CD-ROM drive. A typical location for the CD-ROM drive is shown here.#

The Hard Drive#In your computer, the hard drive is probably located here, although it will fit in several locations.#47#Wherever it is located, it will have two cables attached; the power cable and a 40-pin, flat-ribbon cable. Notice that the flat cable has a stripe on one side. This identifies the edge of the cable that contains pin 1. Be sure to document the orientation of this cable before disconnecting it from the hard drive. Once the cables are disconnected, the four screws that hold the drive to the chassis can be removed and the drive can be lifted out of the computer.#Mother-board48#A typical hard drive cable will look like this. It has two connectors near one end, and one connector at the other. The lone connector attaches to the motherboard. #MasterHard Drive49#The cable supports two hard drives. So which connector do you use? When two IDE hard drives are attached by a single cable, one is the master, the other is the slave. If a single drive is used, it must be the master. The master should be attached to the end connector as shown here. Since you have a single drive, it is the master and it should be attached to the end connector.#SlaveHard Drive

50#If you were using a second hard drive on this cable, it would be the slave and it would be connected here. #When installing ribbon cables watch for:Cable should match connector.Pin 1 of cable to Pin 1 of connector.Missed columns or rows of pins.#Here are some tips to keep in mind when working with ribbon cables. #52#If you document everything carefully, you should have no trouble matching the cable to its connector. If you do not document, sometimes you can still match the cable to its connector by comparing the cable and the various connectors.#153#You must align the cable so that its pin1 goes to pin 1 on the connector. Recall that Pin 1 on the cable is identified with a color stripe. A number screened on the circuit board often identifies pin 1 on the connector. #Missed Row of Pins54#A common mistake when plugging in ribbon cables is to miss a whole row of pins on the connector as shown here. It looks so obvious when shown like this, but it happens all too often. #Missed Row of Pins55#You should check both the top and bottom of the connector to make certain you have not missed one of the rows of pins.#MissedPins56#Here is another variation of the same problem. Here the two end pins are left disconnected. You should check both ends of the connector to make certain that none of the pins are missed.#

The Floppy Drive#Here you see a typical location for the floppy drive.#58#Like the hard drive, the floppy drive has a power cable and a flat ribbon cable. However, once everything is disconnected, the floppy drive usually slides in and out the front of the computer.#59#The floppy drive is held in place by four screws, with two on each side. Some computers use latching rails to secure the drive in place.#60#The most confusing part of installing a floppy drive is connecting the ribbon cable. Often the floppy drive cable will have five connectors like this one. Without good documentation, it can be intimidating.#Mother-board61#Lets see if we can sort things out. First, notice that there are four connectors near one end of the cable and one lone connector on the other end. This lone connector goes to the motherboard.#5"Drive5"Drive62#Next, lets turn our attention to the four connectors at the other end. Notice that two are large and two are small. The two larger connectors are designed to fit the older, and larger, 5-inch floppy drives.#3"Drive3"Drive63#The smaller connectors are designed to fit 3-inch floppy drives. You know that your computer uses a single 3-inch floppy drive. So obviously, it uses one of these smaller connectors. But which one?#Drive AAfter twistDrive BBefore Twist64#Fortunately there is an easy way to remember. Your floppy drive is called, and is configured as, Drive A. If you added a second floppy, you would configure it as Drive B. Which drive goes where is determined by the twist in the cable. Starting from the motherboard and following the cable outward, Drive A attaches to the connector after the twist. Drive B attaches to the connector before the twist. Simply remember: A is after; B is before. #1.Remove the screw.65#Another task that you will have to do frequently is remove or replace an ISA expansion board that is plugged into the motherboard. There is a proper way to remove these boards. First, remove the screw that secures the ISA board to the back panel of the chassis. Your computer uses only one screw. (We will be discussing ISA expansion slots in a later exercise.)#2.Rock the board end to end...66#With the screws removed, grasp the board by the top edges, and gently rock the board end to end. Do not rock it side to side, and do not flex the board.#... up and out of its socket.67#Rock the board end to end until it is free. Then lift the board up and out of the computer. Place the board immediately into an anti-static bag.#

The AGP Video BoardVideo BoardAGP Slot#Video boards installed in AGP slots, as shown here, require special attention. Do not rock them, pull them straight up and out. #Field Replaceable Units (FRUs)Units that can be replaced in the field with common hand tools.#Everything that can be removed from the computer with common hand tools like a screwdriver is called a Field Replaceable Unit, or FRU. As the name implies, these are the types of units that can be replaced in the field. Normally, components that must be de-soldered are not repaired in the field. #Keep these tips in mind.Document everything.Shut off power.Protect against ESDuse antistatic wrist strap.Grasp connectors by shells, not by leads.Never use force.Release latches on connectors.Rock boards end to end.#Well, there you have it. You are now ready to try your luck at examining the computer. Keep these tips in mind as you do it. Document everything in enough detail so that you can put the computer back together again. Shut off the power before disconnecting anything. Protect against electrostatic discharge. Always wear an antistatic wrist strap whenever the computer is open. When removing connectors, grasp them by their shells; never pull on the leads. Never use excess force. If something doesnt come loose using reasonable force, look for latches, tabs, or screws holding it in place. Remove daughter-boards from the motherboard by rocking them end to end. With reasonable precautions, you can take the computer apart and put it back together again so that it works the first time, every time. #Now, its your turn.#Be sure to follow this advice as you proceed to the hands-on exercise.#