Computer Repair I

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The logo of the CompTIA Authorized Curriculum Program and the status of this or other training material as "Authorized" under the CompTIA Authorized Curriculum Program signifies that, in CompTIA's opinion, such training material covers the content of the CompTIA's related certification exam. CompTIA has not reviewed or approved the accuracy of the contents of this training material and specifically disclaims any warranties of merchantability or fitness for a particular purpose. CompTIA makes no guarantee concerning the success of persons using any such "Authorized" or other training material in order to prepare for any CompTIA certification exam. The contents of this training material were created for the CompTIA A+ certification exams #221 and #222 covering CompTIA certification exam objectives that were current as of August 31, 2001.

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Name - _

Class _

Computer Repair Program

I

Safety Lesson

Introduction to Computer Repair

All rights reserved. No part of this book may be duplicated or reproduced in any form without the specific written permission of CES InCiustries, Inc. The use of this manual and the experiments described is restricted to performance with CES Ed-Lab training eguipment and is prohibited from being used with any other training aid or electronic

components or for other educational purposes. CES makes no

representation that the circuits, logic, or programs described herein will not infringe on existing or future patent rights. There is, furthermore, no imf)lication in the granting of licenses to make, sell, or use any circuits, logic, or programs described herein. This does not restrict use of any materials or data sheets which may be available from other sources.

ISBN0-86711-258-1

Printed in the United States of America

CES INDUSTRIES, INC.

Educational Products Division 130 Central Avenue

Farmingdale, New York 11735 Phone (631) 293-1420

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CES INDUSTRIES, INC.

130 Central Avenue, Farmingdale, New York 11735

CES COMPUTER REPAIR PROGRAM

Book

I

I. Safety Lesson

Safety Lesson

II. Introduction to Computer Repair

1 Lesson 1 Lesson 2 Lesson 3 Lesson 4 Lesson 5 Lesson 6 Lesson 7 Lesson 8 Lesson 9 Lesson 10 Lesson 11 Lesson 12 Lesson 13 Lesson 14 Intro to Computers The Keyboard The Monitor

The Power Supply The Floppy Disk Drive The Hard Disk Drive The Motherboard The CPU/BIOS/BUS The RAM

The Video Card

The Multimedia System The Printer Network Systems Computer Viruses 13

23

31

37

45

57

67

75

85

93

103 111 121 127

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Safety Lesson

Objectives:

When you have completed this lesson you will be able to:

1. Name the three greatest dangers in working with electronic equipment.

2. Prevent accidents by following safe work habits.

3. Respond properly in the event of an electrical accident. 4. Identify potential risks to equipment, when failing to use ESD

(electro-static discharge) procedures.

5. Be environmentally aware of the hazardous materials associated with computer systems, printers and other peripheral equipment.

Discussion:

Most of the electronic devices we use every day, such as TV sets, hair dryers and lamps, are designed to keep you away from the dangerous voltages inside. However, accidents happen! In this lesson you will learn about the dangers of working with electronic equipment using low or high voltages, how to avoid accidents, and what to do if an accident happens.

There are three main types of accidents, which you must watch out for when working with electronic equipment.

1. Electrical Shock 2. Electrical Fire

3. Injuries from power tools

It is strongly recommended that the instructor and students discuss safety in the laboratory before proceeding to use any equipment.

Electrical Shock

Electrical shock is what happens when an electric current flows through your body. How dangerous the shock is depends on how

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Safety Lesson

sensation. You might be thrown back away from the source of the current. Or you could freeze on the circuit, unable to move Or let go, stop breathing and go into ventricular fibrillation. This is a condition where your heart cannot keep its rhythm and so cannot supply your body with the blood you need to live.

If you see someone who is receiving an electric shock and is unable to move, you should without touching the equipment or the person, try to shut off the power as soon as possible. Unplug the equipment or shut it off with a book or other nonmetal object. If you cannot shut off the power, then you must try to disconnect them from the equipment as quickly as possible. Do NOT use your bare hands to move someone who is in this condition. You may also get a shock. Use a dry blanket or a jacket or other piece clothing to insulate yourself from the person getting the shock.

Check the person for normal pulse and breathing. If they are not

breathing, then call for help immediately. See if there is a doctor or

s---nurse, or anyone else with medical training that can help. If you

can't find anyone who can help, then begin artificial respiration while someone goes for help. How to give artificial respiration is explained later in this lesson.

Preventing Electric Shock

1. Do not use or even touch anything electrical while you are wet or near water.

2. Always make sure that electrical equipment is completely off before working on it. Unplug the equipment before you work on it and make sure no one can plug it in before you are finished working on it.

3. Do not operate any electrical equipment with wires hanging loose, protective covers off or safety switches defeated.

4. Insert grounded (three prong) plugs into grounded outlets. Do not use 3 wire ground adapters to make them fit into a two prong outlet.

5. Don't use any wires that are damaged or look like they may break.

6. Disconnect power cords carefully. Do not pull plugs out by the wire.

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Safety Lesson

Electrical Fires

1. Electrical fires are usually caused by short circuits or by an overload of the circuit that your are connecting the equipment to. A very large current flows, which overheats the equipment and starts the fire. Never touch any equipment that is burning or smoking. Shut the power off as quickly as possible, but never touch the equipment.

2. Never throw water or use a water filled fire extinguisher on an electrical fire. You may get a shock or even make the fire worse. Only use a fire extinguisher that has been rated for use on live electrical equipment, the NFPA (National Fire Protection Agency) designation of Class 'C' indicates that it is approved for use on live. electrical equipment. The most common fire extinguishers found in most shops or laboratories will be tri-class (AB&C) or may be only 'BC' either way, if the letter 'C' is in the class designation, it is safe and proper to use.

There are three types of extinguishers, which are good to use on electrical fires.

They are:

a. Carbon Dioxide - This is a class 'BC' extinguisher and may be used for electrical as well as flammable liquid (Gasoline type) fires.

b. Dry Chemical - This type extinguisher may be a tri-c1ass or 'ABC' type or may be only a 'BC' type extinguisher, and while it will definitely handle a fire in an electronics or computer repair shop, it will destroy any equipment beyond repair that you spray with it. Therefore, is not recommended for use in electronics or computer repair type shops.

c. Halon Gas - This is a class 'BC' extinguisher and may be used for electrical as well as flammable liquid (Gasoline type) fires. It will not destroy the electrical or electronic equipment that it is used on. However, halon has fallen out of favor due to the fact it is a CFC (chlorofluorocarbon) type gas, which is known to affect the ozone. layer.

Tools used in electronics

Most tools used in electronics are safe, if they are used properly. Screwdrivers, knives, wire cutters, and other sharp tools should be treated with respect. Do not use excessive force. If you have difficulty getting a job done with one tool, find another tool that will

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Safety Lesson

Don't throw or play with tools.

Make sure a tool is in good condition before you use it. Check hammers before use to make sure the head is attached tightly to the handle. Make sure that power tools have good cords on them and that all the safety shields are properly attached. When using drills, saws, or other power tools, clamp your work down before starting. Keep your fingers away from moving parts, and always use eye protection.

Don't leave power tools lying around plugged in when you are not using them. Soldering irons are especially dangerous and can give someone a serious burn. Unplug your soldering iron immediately after you are done using it and don't leave it before it cools off. Just think of what a tool that can melt metal can do to someone's skin.

Minor Injuries:

If someone receives a minor cut or burn, it should be washed in cold water immediately. Get medical help as soon as possible. If a major injury occurs and someone is bleeding heavily from an arm or leg, try to slow down or control the bleeding by applying direct pressure to the injury. If possible elevate the injury to reduce or stop the flow of blood. Observe universal precautions about exposure to blood and body fluids by having rubber or latex gloves in the shop, so that you can protect yourself from diseases transmitted by blood and body fluids.

Artificial Respiration

Always check for a pulse and see if the victim is breathing. If they have a pulse and they are breathing DO NOT start artificial respiration or CPR. Have someone call for professional medical assistance.

Artificial Respiration

Begin immediately to use artificial respiration if the victim is not breathing:

a. Turn the victim on his or her back.

b. Clean the mouth, nose, and throat. If they appear clean, start artificial respiration immediately. If foreign matter is present, wipe it away quickly with a cloth or your fingers.

c. Place the victim's head in the "sword-swallowing" position-(Place the head as far back as possible so that the front of the neck is stretched).

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Safety Less.on

d. Hold the lower jaw up. (Insert your thumb between the victim's teeth at the midline - pull the lower jaw forcefully outward so the lower teeth are further forward than the upper teeth. Hold the jaw in this position as long as the victim is unconscious).

e. Close the victim's nose. (Compress the nostrils between your thumb and forefinger).

f. Blow air into the victim's lungs. (Take a deep breath and cover the victim's open mouth with your open mouth, making the contact air-tight. Blow until the chest rises. If the chest does not rise when you blow, improve the position of the victim's passageway, and blow more forcefully.

g. Let air out of the victim's lungs. (After the chest rises, quickly separate lip contact with the victim, allowing him or her to exhale.)

h. Repeat steps (f) and (g) at the rate of 12 to 20 times per minute. Continue rhythmically without interruption until the victim starts breathing or professional assistance arrives

Electro-Static Discharge and Damage to Electronic Equipment

Electro-Static Discharge or ESD can permanently damage or destroy the electronic components that are used with all personal computers. It is possible that on a dry day, the act of walking across a carpeted floor with rubber sole shoes can produce a static charge of several thousand volts of electricity. While this electricity lacks the current or force to do any physical harm to a healthy human, the charge can be lethal to the computer. It becomes absolutely necessary to use the proper techniques to prevent damage to the computer from ESD. Following a few simple rules early in your course of study, will help prevent accidents in the future.

Basic ESO (electro-static discharge) Protection Procedures Proper Procedures for ESD protection: In order for damage to take place from ESD, the voltage and small current must pass through a component or components on the computers main board or on any of the associated circuits contained in the computer. When the electrical charge passes through a component, the voltage and current is at a high enough value, that it can actually punch a hole through the semiconductor material, thereby rendering it useless.

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Safety Lesson

are becoming smaller each dayI with the average size of an

internal component being .8 microns in size. The ESD charge is similar to dropping a bomb on the middle of an active runway. To prevent the ESD from damaging a computer, the following procedures should always be followed.

A. Always unplug the computer from the electrical supply. While some technicians will argue that keeping the computer connected to the AC (alternating current) outlet allows for a direct connection to the AC ground, more computers have been damaged by accidentally inserting or removing an expansion card or component with the power on.

B. Always wear and properly use, an approved ESO Ground Strap. The ESD ground strap will protect you and the equipment from developing any electrical charges that can damage the computer. It is very important that you use a Ground Strap that is an ESD approved ground strap and not simply a piece of wire that you attach to your wrist and to ground. The approved ground strap will discharge the electrostatic charge with out connecting you directly to ground. Thus any problems that may be associated With the computer or any peripheral you may be working on, will not cause you to become part of the electrical circuit and potentially electrocute yourself in the process.

C. Always use an electrostatically protected work surface or mat. This prevents the build up of static electric charges. The work surface should be ESD protected. While this may not be always possible when performing a field repair, good static protection procedures will prevent damage to a computer.

D. Always touch the bare area of the computer case before beginning the repair. ESD can only occur when there isa difference of potential or a voltage difference between the technician and the computer. Touching the case equalizes this charge.

E.

When removing parts and components from the computer, always place them on the anti-static surface. Whenever possible use an anti-static mat that is properly grounded to prevent damage to the component or component~, removed from a computer. If an anti-static mat is not available, be sure to use a clean area, free from any scraps of wire, aluminum foil or any other conductive material that may cause damage.

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Safety Lesson'

Caution:

Some

tec;hnicians will use aluminum foil instead

of

an

antistatic mat

to

place components on. This is

a

very dangerous process. Most main boards contain a battery, either lithium

or

nickel-cadmium, both

of

which can explode if they are shorted. Placing the board onto aluminum foil will short the battery terminals and may result in

an

explosion, possible fire

or

personal injury.

1. The Computer Power Supply

While the output of the supply is a low voltage between 5 and 12 volts, the input voltage is directly connected to the ACline. This voltage is 120 VAC (voltsAC) at currents as high as the circuit breaker feeding the outlet. In a business environment, the current to an individual outlet may be as high as 30 amps. Once a cover is removed from the power supply, the technician may be exposed to voltages and currents that can injure or kill. Field technicians rarely, if ever, will repair a power supply on site. They will simply replace it and or repair it back in the shop.

2. The Computer Monitor

The computer monitor is basically a television monitor and as such, has the same type of circuitry inside it. The Picture Tube or CRT (Cathode Ray Tube), is a fragile glass envelope, that is under a high vacuum, and if dropped, the tube can implode violently causing pieces of glass to fly in all directions. The CRT also stores an electrical charge, due to the construction of the CRT, it is possible for the tube to hold a charge for several months. This charge can be several hundred to several thousand volts. The most common monitors, 14" and 15" CRT's usually have a charge of 20 to 25 thousand volts applied to them. In addition to the CRT and its associated ability to store an electrical charge even when not turned on or plugged in, the monitor itself operates on voltages significantly higher than those found inside the average personal computer. Normal power supply voltage for a monitor is between 120 and 180 volts, with special power supply voltages of 400 to 1600 volts for deflection coils, and focus circuits. If you are not specifically trained in the service or repair of monitors and their associated dangers, do not open the back covers.

3. The Laser Printer

Laser printers utilize

a

process similar to a photocopy process and as such, use a series of charging wires called Corona

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Safety Lesson

fuser rollerto permanently fix the image on to the paper. These rollers operate at temperatures as high as 195 degrees Celsius. The rollers are under high pressure from springs that maintain· a constant pressure on the rollers surface and may be as high as several hundred pounds, depending upon the printer. The imaging process involves the use of laser light; this laser light utilizes the infra-red spectrum, and as such is invisible. While the output of the laser is only a few milliwatts or 1000 times less than a conventional night-light, it is still possible, especially if the light source shines directly into the eye, to cause damage to the eye. Therefore, when working on a laser printer, one should never bypass any safety interlocks associated with the safe operation of the printer, and most importantly, if you are not trained to repair the printer, you should not attempt it.

4. Dot Matrix Printers

A dot matrix printer like any printer has moving parts, which pose a pinch risk to fingers, hair, ties and any other object that may get in the way of the moving print head. The print head, when printing for sustained periods of time can become very hot, and cause severe burns on contact with exposed skin.

5. Ink-Jet Printers

An Ink-Jet or Bubble-Jet Printer has the same moving parts hazards as a dot matrix printer, however it does not have a print head that can become hot enough to burn skin. The major safety risk from an ink-jet printer is to the work area and the technicians clothing. The inks stain very quickly, and are normally not water-soluble, it is possible to go around with the results of your repair for weeks, after spilling the ink on your hands or cloths, not to mention the customers white carpet.

6. Phone Modems

In addition to ESD precautions, the phone modem presents the technician with the distinct possibility of a nasty shock if not disconnected from the phone jack. The phone network normally operates with an operating voltage of -48 volts DC. When all the phones connected to the same line as the modem, are on the hook or hung up, this -48 volts is enough to give the technician a mild buzz, if they should happen to connect directly across the red and green phone lines. If the technician should happen to be lucky enough to be touching the phone line when it rings, the voltage on the line jumps up as high as 98 to 140 volts AC while ringing. This will cause the technician immediate discomfort, and may cause injury to himself, or others around when the tool or tools they may be holding go flying across the room. Always

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Safety Lesson

disconnect the modem from the phone line before performing any repair to a computer equipped with a modem.

7. Uninterruptable Power Supplies [UPS]

These power supplies use batteries to produce AC output. The same type of AC current that is available at a normal household or business outlet. The voltages available at the output of a UPS are lethal. Most UPS models can produce 120volt~ at up to 20 amps of current. In addition the voltage is present even if the power to the building or outlet is off. The batteries in a UPS will· cause a fire or severe burns if they are shorted in any way. Treat a UPS with the same respect as an outlet, even though the unit is working on a battery.

Disposal procedures for batteries, cathode ray tubes and other environmentally sensitive items

1. Nickel-Cadmium batteries. These batteries while rechargeable several hundred times, do have a finite life span. When this type of battery is "dead" and can no longer be recharged, it should be recycled and not disposed of in the general waste stream. Cadmium is a dangerous heavy metal compound that can pollute ground water if not properly disposed of.

2. Lithium, Lithium-Ion batteries. While these batteries are not as dangerous to the environment as the Nickel-Cadmium battery, they should be recycled whenever possible

3. Lead-Acid, Sealed Lead-Acid or Gel Cell type batteries. All of these batteries contain lead, which must be recycled.

4. Laser Printer Toner Cartridges, these cartridges have a given life span, if they are not being recharged and reused, they should be recycled for the many parts that are contained within the cartridge. Most manufactures of printer or personal copier cartridges have some type of recycling program available to return the old used cartridge directly to the manufacturer for recycling.

In general, for all disposable items, check with local ordinances regarding the availability of and requirements for recycling and the disposal of batteries, office waste, and possibly hazardous materials.

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Safety Lesson

Proper steps to safely discharge a Cathode Ray Tube (When applicable)

As previously discussed, the CRT is capable of holding a significant electrical charge for long periods of time. It is necessary to discharge the CRT before performing any work on the monitor or CRT. The following procedure is a safe and correct method of discharging the CRT.

1. Turn the power to the monitor off, and remove the AC line .cord from the outlet.

2. Using a wire with a series resistor and alligator clips on both ends, clip an end to a non-painted chassis portion of the monitor.

3. Place one hand behind your back so that there is no possible way to complete a circuit while discharging the CRT.

4. Clip a small insulated screwdriver to the free end of the wire 5. Locate the "Second Anode Connection" this is the connection

that contains the high voltage wire, that is normally at the top of the CRT and is usually Red.

6. While keeping your one hand behind your back, slowly insert the screwdriver under the protective rubber boot of the second anode connection. It is possible at this time that you may hear some snapping or crackling sounds, this is normal. Allow the screwdriver to remain in contact with the second anode connector for a minimum of 2 minutes to insure that the high voltage has been discharged.

7. Remove the screwdriver from under the cap.

8. Remove the second anode connector by carefully squeezing the connector together and lifting the connector slowly up and away from the CRT.

9. At this time the CRT is completely safe to handle as far as any high voltage shock is concerned. Remember that the CRT is under an extremely high vacuum pressure and

a

crack in the glass may result in a violent implosion of the tube.

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Safety Lesson

Assignment:

Answer the following multiple-choice questions:

1. Which type of accident happens when working with electronics equipment?

a. Electrical Shock. b. Electrical Fire.

c. Injuries from power tools. d. All of the above.

2. Electrical Shock is what happens when an electric current flows through your body.

a. True. b, False.

3, Electrical fires are usually caused by short circuits or by an overload of the circuit that you are connecting the equipment to, a. True.

b. False.

4. Which one is a type of fire extinguisher used on an electrical fire? a. Carbon Dioxide.

b. Dry Chemical. c. Halon Gas. d. All of the above.

5. Artificial Respiration is used if the victim is not breathing. a. True.

b. False.

6. Electro-Static Discharge can permanently damage or destroy the electronics parts that are used with all personal computers.

a, True. b. False.

7. Which one is an ESD protection procedure?

a. Always plug in the computer to the electrical supply.

b, Always use an electro-statically protected work surface or mat. c. Always wear an ESD Ground Strap.

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Safety Lesson

8. Which is a basic ESD protection device? a. ESD approved ground strap.

b. Aluminum foil. c. Both a and b. d. None of the above.

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Introduction to

Computers

Objectives:

When you have completed this lesson, you will:

Lesson

1

1. Be able to assemble the CES 975 Computer Repair Trainer into a working computer.

2. Use the CD-ROM Drive to access the "How Computers Work" program in Windows 98.

3. Understand the special turning-off procedure for Windows.

Materials Needed:

1. CES Computer Repair Trainer Model CES 975. 2. CES Computer Repair Module Manual.

., Po\O/ER SUPPLY .IS CONNECTED TO EACH AND EVERY MODULE

POWER _r-- _{CD ROM} SUPPLY MONITOR

!

~

EXPANSION KEYBOARDlU SLOTS CONNECTOR

I:

MEMORY_MODULESRAM

~I

MOTHERBOARD HARD FLOPPY ~ IcPul C~frt1E(1 DISK DISK _KEYBOARD MEMORY

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Lesson 1

Discussion:

Introduction to Computers

1. The personal computer industry has become one of the fastest growing areas of technology today. This caused an . increasing need for trained computer repair technicians in the job market. A computer repair technician must have a complete understanding of all of the hardware, programs, peripherals, and in some cases an understanding of networks and communications.

This module is designed to provide the basic knowledge and understanding of the personal computer, its functions, operations, components and software. Only then can we begin to work on the skills and procedures necessary to service, repair, maintain an(j troubleshoot the personal computer of today.

The main objective of each experiment in this computer repair module is to introduce you to the function of each of the major components of a personal computer. They will familiarize you with the proper operation as well as discuss the symptoms associated with a failure and teach basic troubleshooting skills. Since this is a modular program, the intention of this program is not to. actually take the computer apart and physically change the defective component, but to help you learn how to "successfully" complete the repair. This course will not get involved with the "setting up" of a personal computer. Simply put, we assume that the computer that you are working on was already built, and did work at one time.

Setup procedures for advanced operation such as CMOS

(Complimentary Metal Oxide Semiconductor) configuration or software configurations will not be covered in this module.

Each lesson that you are about to start will begin with a discussion of the topic, followed by a specific procedure that you are to complete. A fault or trouble is inserted into the computer, followed by a discussion of the proper repair procedure associated with that fault.

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'" POVER SUPPLY IS CONNECTED TO EACH AND EVERY MODULE

POWER _~ _{CD ROM} SUPPLY

J

MONITOR ~ EXPANSION KE'IBOARD~[J SLOTS CONN~ RAM MEMORY MODULES MOTHERBOARD

-HARD FLOPPY

I

§]~

~!~~'1

DISK DISK _KEYBOARD

2. The personal computer is a modular system, consisting of many separate components that when connected correctly function as a complete computer.

3. Proper troubleshooting skills require the proper tools. The tools most often used by a technician in the field, consist of a good magnetic screwdriver and an anti-static wrist strap. Some professionals will cringe at the thought of using a magnetic screwdriver anywhere near a computer. They believe that damage can be done to the disk drives inside the computer. In fact, the only damage that you can cause is erasing a floppy disk if you accidentally place the screwdriver directly on top of the disk. It is possible to magnetize an area of the computer monitor and cause the· color purity to be effected if the screwdriver comes too close to the monitor. A good general rule when working with a magnetic screwdriver, is to keep it in your pocket when you are not using it to remove screws.

Lesson 1

4. Anti-Static Protection

Whenever you work on any electronic equipment, the possibility of damage from static electricity is great. The simple act of walking across a nylon carpet, can cause your body to develop a static charge of several thousand volts. The charge, if discharged into a component of the personal computer, will most certainly damage,if not destroy the component. To prevent this from happening, good anti-static protection should be used.

The normal practice for static protection is to wear an anti-static wrist strap. This strap is conductive and will discharge any static

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Lesson 1 Introduction to Computers

correctly if it is connected to a proper ground. In addition, whenever working on a computer system, most technicians will keep the AC power cord connected to the AC outlet, thereby maintaining a connection to ground to aid in static protection.

If your instructor is uncomfortable with keeping the AC cord plugged in while you are working on the computer, a wire with alligator clips on both ends can be attached to the frame of the computer and to the faceplate of the outlet, which will also provide static protection.

Procedure:

1. Please locate the following components to the CES Computer Repair Module Model CES 975:

A. CES Computer Repair Trainer Model CES 975 B. Power Cord for the Computer Repair Trainer C. Monitor (with power cord and cable)

D. Mouse

E. Keyboard

F. Printer (with printer cable)

G.CO-ROM "How Computers Work" H. Stereo Headphone Jack

I. Blank 3 %"disk

2. Connect the cable from the monitor to the video adapter that is on the right side of the CES Computer Repair Trainer.

3. Connect the keyboard cable to the keyboard connector. 4. Connect the mouse cable to the mouse connector.

5. Connect the computer power cord to the power supply on the trainer.

6. Connect the printer cable to the printer and to the computer trainer. 7. Connect the headphones to the headphone jack, which is located

near the printer cable connection.

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8. Plug the computer power cord, the monitor power cord, and the printer power cord into the outlet.

9. Turn the monitor power switch to the "on" position now. Wait a few seconds until the monitor warms up and then proceed.

Lesson 1

10. Turn the main power switch of the CES Computer Repair Trainer to the "on" or up position now.

With the "ATX" style computer, the main power switch is located on the power supply, when the mainpower is on, the user must turn the computer on by depressing a momentary switch located at the back of the trainer.

With the "AT" style computer; the main power is turned on by only a large toggle switch located at the back of the trainer.

The Computer is now going through the standard boot-up procedures. In about 30 seconds, you should see a blue screen. This is the normal start-up screen for Windows 98.

At this time it is very important to learn the proper procedure· for turning the computer off. This is commonly referred to as the shutdown procedure.

COMPUTER SHUT-OFF INSTRUCTIONS:

Since the computer repair system uses Windows as its operating system, it is very important to use the correct procedure when turning off the computer.

Failure to use the proper shut-off procedure may result in permanent damage to the computer.

A. Using your mouse, click once with the left mouse button on the start box in the lower left hand corner.

B. Move the mouse cursor to "Shut down" and click the left mouse button once.

C. The computer will ask, "What do you want the computer to do?" Make sure "shutdown" is selected and click on "OK". .With the "ATX" style computer, the computer will shutdown on

it's own.

D. With the "AT" style computer, the computer will tell you "It's now safe to turn off your computer".

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You have just properly turned off the computer. To continue the lesson, please re-start the computer now.

For the balance of this lesson, you will be using the CD-ROM "How Computers Work".

11. Before continuing with this experiment, you will notice that there is an expansion card installed in the computer that has two seven segment displays. This is called a POST Diagnostics Card.

The purpose of this card is to interpret information that is sent from the BIOS (Basic Input Output System) during the startup or boot procedure. During the start up or boot procedure,a special program called the Power On Self Test or POST is automatically executed. This program will test the various major components and determine if they are present, and if they are present, are they working correctly.

12. Each test that the POST will execute has a unique number associated with the test, this number is sent out on the expansion bus as each test is started. If you have the special hardware required to read this information, the code numbers will be displayed. When a component or device fails, the code that is displayed is the number that represents the test that has just been started. A list of these test codes can be obtained from. the manufacturer of the main board. With this information, it is possible to determine what test has failed, and therefore, a course of action in repairing the system.

Each machine will have different internal code numbers representing the various steps within the POST program. You.may not always have the correct code available for the system that you are servicing and unfortunately these codes can change from motherboard to motherboard manufactured by the same company. 13. Before continuing this experiment, note what number is displayed

on the POST Card Display, NOW. The number displayed is the NORMAL or WORKING state of this individual computer, and will be displayed each and every time the computer is started and successfully completed the POST.

14. The CD-ROM drive is located on the right side of the trainer. Open the CD-ROM tray by pressing the button on the right side of the CD-ROM drive.

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15. Insert the CD-ROM "How Computers Work" into the drive with the label facing up. Do not touch the bottom surface of the disk.

16. Close the CD-ROM tray by pushing the button again. 17. Put on your stereo headphones.

Plug the headphones into the jack on the right side of the trainer near the key switch.

18. Use the mouse to double click on the icon "How Computers Work". (Left button)

19. If a warning occurs on the screen, click on "OK".

20. You are about to go on an overview tour ofthe computer. Move the mouse cursor to 'Tours" and click once.

21. Now, move the mouse to "overview" and click once.

This multimedia presentation should last approximately 12 minutes. Sit back and enjoy III

22. When the final "Run a Program" section is finished, click on "Main". 23. Now click on "Exit" to exit the program.

24. Click on "OK" when asked "Are you sure you want to leave?" 25. Click on"'OK" again.

You have just exited the multimedia program.

Lesson 1

Review:

CPU - stands for "Central Processing Unit". It handles and controls all input and output of information.

Multimedia - is the merging of video and audio, and program files to produce a presentation.

Bootup - is the process of powering up a computer system. It looks for certain start-up instructions, which are stored on chips, such as the BIOS chip.

Formatting a disk - it puts information on the disk so that the operating system knows where and how the files are stored.

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I/O device - stands for Input and Output devices such as: 1. Keyboard (input device)

2. Floppy Disk Drive (input or output device) 3. Printer (output device)

4. Monitor (output device)

5. CD-ROM (input or output device)

6. Hard Disk Drive (input or output device)

Memory/Storage - the Computer has two ways to store information. 1. Memory or RAM (Random Access Memory)

2. Disk Drives (Hard or Floppy)

Run a Program - the process by which the computer· loads a program into the memory, then follows the instructions contained in the program to perform a given task, such as running the multimedia disk - "How Computers Work".

Assignment:

Answer the following multiple-choice questions: 1. The CPU:

a. Handles the input and output of information. b. Performs basic arithmetic (math) functions. c. Means Central Processing Unit.

d. All of the above.

2. During the boot-up process, the computer checks to see if a: a. A boot disk is available.

b. Video card is installed in the computer.

c. Keyboard is plugged into the keyboard connector. d. All of the above.

3. The BIOS ROM Chip tells the operating system:

a. What hard drive type is installed and how to.interact with it. b. What video card is installed.

c. How much RAM memory is installed. d. All of the above.

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4. Which one is just an output device? a. Keyboard

b. Disk Drive c. Printer d. Mouse

5. Which one is just an input device? a. Disk Drive

b. Keyboard c. CD-ROM d. All of the above

6. How many ways can the computer store information? a. Two

b. One c. Six d. Four

7. What does RAM stand for? a. Random Access Memory b. Random And Memory c. Read Only Memory d. Random Write Memory

Lesson 1

8. Which type of storage devices does the computer use as its main storage device?

a. Floppy Drive b. Hard Drive c. CD-ROM d. All of the above

9. Formatting a disk means that the computer's operating system, puts disk information and instructions on a hard drive or floppy disk, so that the operating system knows where the information is stored, what information is stored and how much free space is available on the disk.

a. True b. False

10. Multimedia is the merging of video and audio files to produce a presentation such as the presentation that you have just seen and heard in this lesson.

a. True b. False

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The Keyboard

Objectives:

When you have completed this lesson, you will: 1. Understand how the keyboard works.

Lesson

2

2. Understand how the keyboard communicates with the system unit. 3. Be able to locate and identify a common fault associated with the

keyboard.

Materials Needed:

Discussion:

1. The keyboard that is used with the personal computer is nothing more than a group of switches that have been arranged into a combination of rows and columns. The keyboard is connected to the motherboard by way of a 5 conductor cables and connectors, which is connected to the keyboard input on the motherboard. 2. The five conductor cable includes the following signals:

a. Power (+5 Volts) b. Ground

c. Serial Data out to the motherboard d. Keyboard signal reset

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Lesson 2 The Keyboard

Inside the keyboard

3. The keyboard utilizes a plunger attached to each of the mechanical keys that press against the contacts to form a complete electrical circuit.

4. Inside the keyboard is a micro-controller or simply a small computer that has only one task to accomplish. The micro-controller constantly looks at each of the individual keys through a process called scanning. When a key is pressed, the microcontroller then interprets the key press into what is called the "key scan code". The scan code is a numerical representation of what key was pressed. The scan code consists of two parts for each key on the keyboard, the scan code that represents a key down, or when you pressed the key and a scan code that represents a key up, or when you released the key.

5. This information is then converted into a serial data stream and sent to the computer system by the keyboard microcontroller. The keyboard controller on the motherboard converts the serial information coming from the keyboard. It then signals the CPU (Central Processing Unit) by way of the interrupt control system that there is keystroke information to be processed. The CPU is interrupted from the task or program that it is currently doing to service or process the interruption, in this case, the interruption is the keystroke or keystrokes you typed on the keyboard.

Equipment Setup Procedures:

If your Computer Repair trainer has not been setup, ask your teacher for the equipment setup procedure sheet before beginning the following procedure.

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The Keyboard

Procedure:

1. Open the CD-ROM tray.

2. Insert the CD-ROM "How Computers Work" into the Drive. 3. Close the CD-ROM tray.

4. Put on your stereo headphones.

5. Use the mouse to double click on the icon "How Computers Work". 6. When a warning occurs on the screen, click on "OK".

Lesson 2

7. When the music starts and the title screen appears move the mouse cursor anywhere on the screen and click once using the left mouse button. This will help the user to quickly start the program by bypassing the title screen and make the music stop playing. 8. You are about to go on a tour of the Keyboard.

Move the mouse cursor to the picture of the Keyboard on the monitor and click once.

Sit back and enjoy II!

9. After you have listened to the description of the Keyboard, move the mouse cursor to the back of the computer and click once. 10. Now move the cursor to the "Keyboard Port" and click once.

Sit back and enjoy ,!!

11. When the tour of the "Keyboard Port" is finished, click on "Main" to go to the main menu.

12. Click on "Exit" to exit the program.

13. Click on "OK" when asked "Are you sure you want to leave?" 14. Click on "OK" again.

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Lesson 2 The Keyboard

Computer Repair and Fault Insertion:

I

Fault Insertion

I

1. Please follow the correct procedures in turning the computer repair trainer "OFF".

COMPUTER SHUT-OFF INSTRUCTIONS:

Failure to use the proper shut-off procedure may result in permanent damage to the computer.

C. The computer will ask, "What do you want the computer to do?" Make sure "shutdown" is selected and click on "OK". With the "ATX" style computer, the computer will shutdown on it's own.

D. With the "AT" style computer, the computer will tellyou "It's now safe to turn off your computer".

E. Turn the computer OFF.

F. Ask your instructor for the key to the key switch located on the right side of the trainer.

G. Insert the key and rotate the key to a horizontal position. 2. Move fault switch to position one.

This will insert a fault in the keyboard system. 3. Turn the power

to

the computer repair trainer on.

I

SYMPTOM

I

4. Does the computer repair trainer start normally?

It should not start normally because of the fault inserted in the keyboard system.

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The Keyboard

5. What symptoms did you observe?

You should have observed that Windows does not start normally and that an error message has occurred on the screen. ThePOST (Power On Self Test) detected that there is a failure of a major system associated with the keyboard, and has detected the error. You should notice that the POST Card in the computer has displayed a different code other than the normal boot or start-up code.

I

DIAGNOSISI

6. Based upon these observations, there is a number of possible things that can be wrong with the computer.

Lesson 2

The keyboard may be defective.

With the type of error that you have identified, the keyboard would most likely be the· problem associated with the fault observed. Keyboard failures can occur for numerous reasons, with the most common being a foreign substance like coffee, being spilled onto the keyboard.

The keyboard cable may be defective.

A crimp or other physical damage to the keyboard cable can also generate a keyboard error. Even though the POST has identified a keyboard error, it does not indicate whether the fault is the keyboard or its associated components.

The keyboard port on the motherboard may be defective.

The keyboard may be functioning 100 percent correctly, .but is unable to communicate with the keyboard controller on the main board. This type of problem may be caused by a small 1 amp fuse, located near the keyboard connector, that provides 5 volts to the keyboard via the keyboard cable.

The keyboard controller may be defective.

The. microcontroller in the keyboard may no longer be functional. The motherboard may be defective.

When all other devices have been. tested, and you have changed the components that are easy and the least expensive to change, the only other cause for a keyboard error can be the motherboard itself.

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Lesson 2

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REPAIR

I

The Keyboard

The keyboard is defective.

Replace the keyboard, and re-test the computer to see if the problem has been solved.

The keyboard cable may be defective.

Even if you determine that the problem is the keyboard cable, the cable is part of the keyboard. The normal repair procedure is to replace the keyboard.

The keyboard controller may be defective.

It is impossible to obtain the exact microcontroller used in the defective keyboard. The repair is to replace the keyboard.

The motherboard may be defective.

After changing the keyboard, you have determined that the keyboard error is still present. The most iikely failure would then be, associated with the keyboard circuitry located on the motherboard. The repair procedure for the symptoms stated is to replace the defective motherboard.

Repairing Procedure:

1. Since this fault prevented the computer from starting normally, there is no need to follow a special shut-down procedure.

2. Turn off the main power switch now.

3. Turn fault switch to the original"No Fault" position and turn the key switch to original vertical position.

4. Your computer is now ready to proceed with the next lesson.

Review:

You should have observed that the computer was unable to start normally. The Windows startup screen never appeared. The computers internal diagnostics program known as the Power On Self Test or POST for short, detected that the computer had a defect that was detectable by the diagnostic program. The program responded with an error message that corresponded to the defect that was detected and said, "keyboard error or no keyboard present." "Press {F1} to continue".

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The Keyboard

Assignment:

Lesson 2

1. When pressing the letter K down on the keyboard, the plunger presses against two electrical contacts to form a circuit.

a. True b. False

2. What chip is used first by the computer to decide which key on the keyboard was pressed?

a. RAM b. CMOS

c. Microprocessor

d. 810S

3. The RAM does not hold the scan code until the computer is ready for it.

a. True b. False

4. The CPU chip is used in the keyboard decision-making process. a. True

b. False

5. What is the last chip used in the key decision making process?

a.

CMOS

b. Keyboard controller

c. CPU ' d. 80th A and 8

6. How many types of keyboard ports are there?

a.

One b. Two c. Three d. Four

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The Monitor

Objectives:

When you have completed this lesson, you will: 1. Understand how the monitor works.

Lesson

3

2. Understand how the computer system communicates with the monitor.

3. Be able to locate and identify a common fault associated with the monitor.

Materials Needed:

Discussion:

1. The monitor can be thought of as a specialized television screen. In fact, most of the circuits and components that are associated with the modern color television system, are very similar to the components that are in the computer monitor.

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Lesson 3 The Monitor

2. The major difference between the television and the computer monitor is that the television is able to tune or select different channels and has audio circuits that allow the program audio to be heard. The computer monitor accepts the information to be displayed by way of the video card installed on the motherboard. The video signal is an analog signal that contains the color, synchronization signals and intensity signals. The monitor interprets these signals and displays the information that you see on the screen.

3. There are many different types of monitors, and the type of monitor that you use must agree with the type of video card that you have installed on the computer. The four types of monitors that you may come across are:

• Monochrome or single color, often green or orange screen monitor.

• CGA or Color Graphics Array monitor. • EGA or Enhanced Graphics Array monitor.

• VGA or Super VGA (SVGA), video graphic array monitors. The SVGA monitor is the current and the most common type of monitor.

Equipment Setup Procedures:

If your Computer Repair trainer has not been setup, ask your teacher for the equipment setup procedure sheet before beginning the procedure below.

Procedure:

5. Use the mouse to double click on the icon "How Computers Work". 6. When a warning message occurs on the screen, click on "OK".

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The Monitor

7. When the music starts and the title screen appears, move the mouse cursor anywhere on the screen and click once using the left mouse button. This will help the user to quickly start the program by bypassing the title screen and make the music stop playing. 8. You are about to go on a tour of the Monitor.

Move the mouse cursor to the picture of the Monitor and click once. Sit back and enjoy III

9. When the tour of the Monitor is finished, click on "Exit" to exit the program.

Computer Repair and Fault Insertion:

I

Fault Insertion

I

2. Move the fault switch on the side of the monitor to position one. This will insert a fault in the monitor sub-system.

3. Turn the power to the computer repair trainer on.

I

SYMPTOM

I

You should notice that the computer will start normally, however the information that is being displayed on the monitor appears to be scrambled, somewhat like a cable television station that you are not paying for.

Depending on the type of monitor used you may see diagonal lines or a blank screen. If the screen is blank, it is because you are using a "green monitor". A green monitor blanks out when no video signal is detected. If your screen is blank, set the monitor fault switch to position 2. You will see the Windows desktop appear on

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switch to position number 1. As you rotate the switch, observe the diagonal lines on the screen before it blanks out.

You should have observed, that the computer repair trainer did boot in the normal fashion, as indicated by the post display card on the trainer, however, it appears that the video information on the monitor is scrambled, for a few seconds and then the monitor goes blank (black).

6. Based upon these observations, there are a number of possible things that can be wrong with the computer.

• The video card may be bad.

• The cable to the monitor may be bad. • The monitor itself may be bad.

The interesting part about troubleshooting computers is that surprises happen to the best of us. What you have just experienced is what happens when the monitor you are using has a feature known as a green feature. The green feature is an energy saving feature that the manufactures have installed in accordance with recommendations from the EPA (Environmental Protection Agency) to save energy. Whenever a monitor is not in use for a few seconds, that is a loss of a video signal from the computer, the monitor turns off. What is happening with this fault is that since the video signal has been lost from the host computer, the monitor assumes that the user has turned off the computer but forgot to turn off the monitor, so it shuts off.

I

DIAGNOSIS

I

7. Based upon these observations, you would diagnose the monitor problem as follows.

Defective Video Card

Since the computer appears to be starting normally, and at this time there is no error code displayed on the Post Card, it is possible to assume that the video card is functioning correctly. As discussed in previous experiments, the POST program will only detect a problem associated with primary hardware, and a failure that the POST diagnostic program is aware of. Since the computer did in fact boot, the chances of the video card being defective are small. However, since most repairs are accomplished by

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The Monitor

"replacement", it does not hurt to try changing the video card. For this fault, the problem would remain.

Defective Monitor Cable

Since the monitor cable carries all the information to the monitor for video, synchronization, intensity and color, it is a possibility for the problem to be associated with the monitor cable. A quick, disconnect and reconnect of the cable, or a swap with a known working cable will verify if the cable is indeed the cause of this fault.

Defective Monitor

If, after swapping the cable and the video card, the problem still exists. The cause of the difficulty is in the monitor. For this you would replace the monitor, since the repair of the monitor requires more technical skill and a familiarity with television circuits.

I

REPAIR

I

The problem associated with the computer repair trainer is a problem in the monitor circuitry itself. Since the monitor is a specialized television set, repairing the monitor requires the complete understanding of how video, color and synchronization circuits function. Most field repairs involving monitors are resolved by changing the defective monitor with a known good monitor and sending the monitor back to the manufacturer for repair.

Repairing Procedure:

1. Since this fault did not prevent the computer from starting normally, but the fault was not in the computer system itself, you can remove the fault by turning the Monitor fault switch to the original "No Fault" position,

Review:

The computer monitor displays information that is sent from the video card. The monitor is basically a television set that does not have any tuner or audio circuits, but can display information sent directly from a computer. The monitor that is used with the computer must be the same type of monitor that the video card is designed to operate with, otherwise severe damage may occur to

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The most common monitor that is available today is the super VGA monitor. This monitor has the ability to display 16.7 million colors at a resolution of 1280 X 1024 pixels. Repair of computer monitors are normally limited to those individuals that are trained in the repair of televisions since extremely hazardous voltages are present inside the monitor.

Assignment:

1. The video card is not used by the computer to display images on the monitor.

a. True b. False

2. The electron gun beams bend to create the complete image, so you can see the image on the monitor.

a. True b. False

3. The term "Shadow Mask" means a metal sheet with holes in the middle to help keep the beams aligned with the phosphors.

a. True b. False

4. The beams scroll across the screen horizontally at 60 times a second.

a. True b. False

5. The term "LCD" for laptops means Liquid Crystal Display. a. True

b. False

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The Power Supply

Objectives:

When you have completed this lesson, you will: 1. Understand how a power supply works.

Lesson

4

2. Understand the various connectors and their functions.

3. Be able to locate and identify a common fault associated with the power supply.

Materials Needed:

Discussion:

1. The power supply is connected to the household outlet, which supplies 120 VAC (Volts Alternating Current) power to the computer. The power supply consists of:

• Circuits that change the household power into the power needed for the computer to operate.

• A cooling fan to reduce the temperature inside the computer case.

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Lesson 4

POWER SWITCH

The Power Supply

RED -+50CVOLTS BLACK ] GROUND BLACK YEllOW -+12 L-.J

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+ _q, al I + + _"'0 U'1 _:c ....

....

U'1 ₀ 0 0 ₀ N N 0

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i"l i"l C i"l _I"l"1 < < ;z: _< _:c 0 0 ₀ ₀ r r _r al

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.... -f 0 Vl Vl Vl 0 0

2. The computer needs Direct Current or DC to operate and as such has the following outputs. +5, +12, -12, -5 volts DC. In addition, a special output called the power good signal is sent from the power supply to the motherboard to inform the CPU and the reset control circuits that the power supply is working and that all the necessary supply voltages are present.

3. When the power supply is first turned on, the power good signal is held low, or set at 0 Volts, this prevents the motherboard from resetting and starting the normal boot up procedures, as the power supply voltages increase to their normal levels, the circuitry inside the power supply monitors all of the output voltages. When all voltages are at their correct level, the power good signal changes from low to high or to 5 Volts.

4. Once the power good signal is high, the reset control logic on the mainboard will reset the CPU and start the normal boot procedure. The power supply also incorporates a logic circuit that will detect an overload or a short circuit and will immediately turn off the power. The logic circuit requires that a load be connected to the power supply at all times in order for the supply to even turn on. Therefore, it is necessary always to have something such as a disk drive or motherboard connected to the supply when testing the supply for proper operation.

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The Power Supply Lesson 4

5. The power supply used in the personal computer is known as a

switching power supply, and as such is a complicated circuit. Repairs to this type of supply are limited to the diagnosis of the problem and the replacement of the supply. Unlike all of the components in the personal computer, the voltages that are contained inside the power supply can kill you! Never attempt to open, or in any way modify the power supply unless you are a trained electronics technician familiar with the workings of switch mode supplies.

Equipment Setup Procedures:

If your computer repair trainer has not been setup, ask your

teacher for the equipment setup procedure sheet before beginning the procedure below.

Procedure:

5. Use the mouse to double click on the icon "How Computers Work". 6. If a warning message occurs on the screen, click on "OK".

7. When the music starts and the title screen appears move the mouse cursor anywhere on the screen and click once using the left mouse button. This will help the user to quickly start the program by bypassing the title screen and make the music stop playing. 8. You are about to go on a tour of the Power Supply.

g. Move the mouse cursor to the picture of the computer case and click once on the front of the computer.

10. Then move the mouse cursor to the picture of the Power Supply and click once.

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Lesson 4 The Power Supply

11. When the tour of the Power Supply is finished, click on "Main" to go to the main menu.

12. Then move the mouse cursor to the picture of the computer case and click once on the back of the computer.

13. Then move the mouse cursor to the picture of the Power Supply (Back) and click once.

Sit back and enjoy!!!

14. When the tour of the Power Supply (Back) is finished, click on "Main" to go to the main menu.

15. Click on "Exit" to exit the program.

Computer Repair and Fault Insertion:

I

Fault InsertionI

COMPUTER SHUT-OFF INSTRUCTIONS:

Failure to use the proper shut-off procedure may result in permanent damage to the computer.

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The Power Supply

C. The computer will ask, "What do you want the computer to do?" Make sure "shutdown" is selected and click on "OK". With the "ATX" style computer, the computer will shutdown on it's own.

D. With the "AT" style computer, the computer will tell you "It's now safe to turn off your computer".

E. Turn the computer OFF.

2. Ask your instructor for the key to the key switch located on the right side of the trainer.

3. Insert the key and rotate the key to a horizontal position.

4. Move the fault switch on the computer repair trainer to position two. This will insert a fault in the power supply.

5. Turn the power to the computer repair trainer on.

I

SYMPTOM

I

The computer did not start normally. You should notice that the computer is completely dead. There is no hard disk or floppy disk c;lctivity, the POST card is not displaying any information, and there are no beeps or error codes.

Lesson 4

a. You should observe that the computer did not boot at all. The monitor was dark, however the power on the indicator for the monitor was on. (Note: With some "green" monitors the power indicator light may turn orange, flashing or be off although the monitor is turned on).

b. You also should have noticed that the system had no power on the indicators, the POST card was blank, however, the power indicators (+5,+12,-12,-5) were on.

c. This is a common type of misleading fault, it appears to the casual user that the power supply is on, and working since the fan and some supplies are on.

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Lesson 4

I

DIAGNOSIS

I

The Power Supply

8. This is an easy diagnosis, since the computer is basically "dead". There are very few components in the personal computer that can cause a totally dead machine. The most common is a defective power supply.

9. Based upon these observations, there are several possible things that can be wrong with the computer.

a. Defective Power Supply

b. A Defective expansion card or slot

c. Defective peripheral device connected directly to the power supply

Defective Power Supply

Since the power supply produces all the necessary output voltages for all devices installed in the computer, the power supply would be the first and most likely suspect. Remember the power supply can be good, but the power signal may not be set. This will cause the computer not to start, and will produce a "dead machine"

Defective Expansion Card

If by chance. an expansion card is defective or has a defective component on it that.causes an increased demand in current. The power supply will immediately shut down all output voltages, and this will result in a dead machine. To verify this type of problem, you would remove all the expansion cards, restart the computer and observe the system for signs of a normal boot. If the computer were to start normally, you would replace each expansion card removed, one at a time, until the computer failed to start. This would produce the defective card with the least amount of work.

Defective Peripheral Device

As with a defective card, a defective hard disk, floppy disk, CD-ROM drive, or any device connected directly to the power supply will cause the power supply to shut down. You would troubleshoot this problem the same way by removing all peripherals and restarting the computer. If it starts normally, you would replace each component, one at a time until the offending part is found.

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The Power Supply

I

REPAIR

I

The repair procedure for the symptoms stated will be to replace the defective power supply. Since the power supply is a switch mode supply and is extremely complicated to repair, and the replacement cost ofa new power supply is under $50.00, it is cost effective to replace the power supply with a new one.

Repair Procedure

1. Since this fault prevented the computer from starting normally, there is no need to follow a special shut-down procedure.

2. Turn off the main power switch.

3. Turn fault switch to the original "No Fault" position and turn the key switch original vertical position.

Review:

Lesson 4

The power supply is used to convert household current into voltages and currents that the personal computer utilizes. The supply provides 4 different output voltages and a power good signal to the computer. Inside the supply, hazardous voltages are present and no one should open the supply unless they are totally familiar with the operation.

Assignment:

1. The Power Supply is a device used to convert 120 VAC to a voltage that the computer can use.

a. True. J

b. False.

2. Should you open the power supply to see what the inside looks like or for any other reason?

a. Yes. b. No.

Computer Repair I

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Computer Repair Program

I

Safety Lesson

Introduction to Computer Repair

CES INDUSTRIES, INC.

CES COMPUTER REPAIR PROGRAM

Book

I

Table of Contents

I. Safety Lesson

II. Introduction to Computer Repair

23

37

45

57

67

75

85

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