BASIC COMPUTER TROUBLESHOOTING

Process of identifying the failure of the computer and how to locate the entire electrical/electronic failure. Solving computer problems requires the application of deductive technique called “troubleshooting”. In general there are some optimum steps that you can follow to successfully troubleshooting and repair a computer.

IDENTIFYING PARTS OF A PC

This module discusses what goes on inside your system. It will also explain how your PC components run and give additional information on what type or class each system has.

At the end of the lesson you can identify the function of each components.

Monitor

A Monitor displays text and images generated by different colors and sizes. A monitor is the output of programs that are being viewed by the user.

The size of the monitor is measured diagonally across the screen. Common monitor sizes are 14,15,17 and 21 inches. Larger monitors are more expensive and ideal for desktop publishing and working with graphics or large spreadsheets.

Flat Panel

A flat panel monitor uses liquid crystal display (LCD), which is the same type of display found in most digital wristwatches. In the past, flat panel screens were only used on portable computers, but now full-size flat panel monitors are available for desktop computers.

Dot Pitch

The dot pitch is the distance between tiny dots on a screen. The dot pitch determines the sharpness of images on the screen.

Refresh rate

The refresh rate – determines the speed that a monitor redraws, or updates, images. The higher the refresh rate, the fewer flickers or the screen. This helps reduce eyestrain.

Controls

Monitors have controls to adjust the brightness, contrast and other features of the images displayed on the screen. You can find controls on the screen or on the monitor.

Tilt-and-Swivel base

A tilt-and-swivel base lets you adjust the angle of the screen. This lets you reduce the glare from overhead lighting and view the screen more comfortably.

Screen Saver

A screen saver is a moving picture or pattern that appears on the screen when you do not use a computer for a period of time.

Video Card

This video card is a circuit board that plugs into an expansion slot inside the computer.

The video card controls that quality of what you see on your monitor.

There are five kinds of bus type each video card represents.

1. ISA bus (8 bit Video Slot) Industry Standard Architecture

2. The EISA bus (16 bit Video Slot) Extended Industry Standard Architecture

3. The VESA slot (32 bit Video Slot) Video Electronics Standards Association

4. The PCI bus (32/64 bit Video Slot)

5. And the AGP (64/128 bit Video Slot)

A video card has memory chips. These chips temporarily store information before sending it to the monitor.

Types of Video Cards:

VRAM

Video Random Access Memory (VRAM) is type of memory specifically designed for video cards. VRAM is ideal for displaying complex graphics.

AGP

An Accelerated Graphics Port (AGP) video card uses an AGP but to communicate directly with your computer’s main memory. This allows you to quickly display complex graphics on your monitor.

Types of Video Card

CGA or Color Graphics Adapter is being used without having any graphics and limited color capability. The graphics resolution was low enough that it could not support high quality text.

HGC or Hercules Graphics Adapter it adds and better screen resolution over CGA and this higher quality-text and graphics to the capabilities of a CGA, although the screen resolution is still limited.

EGA or Enhanced Graphics Adapter it adds colors and better screen resolution over CGA and this higher quality text and graphics to the capabilities of a CGA, although the screen resolution is still limited.

VGA or Video Graphics Array is the standard in Video Card. It allows increase in graphics resolution to 640 x 480 with the 16 colors.

SVGA or Super Video Graphics Array is the extension of VGA with the standard mode of 256 colors on screen at once.

Keyboard

Keyboard is the external part of computers. Most of the input to your computer is through the keyboard. Despite being simple devices in concept, good keyboards are relatively complex to build. Most keyboards have 101 keys.

Escape Key – is used to quit a task you are performing.

Caps Lock – and Shift Keys – let you enter text in uppercase (ABC) and

lowercase (abc) letters.

Control and Alt Keys – in combination with another key to perform a specific

task. For example, in some programs you can press CTRL and S to save a document.

Function Key – lets you quickly perform specific tasks. For example, in many

programs you can press F1 to display help information.

Backspace Key – is used to remove the character to the left side of the cursor.

Delete Key – is used to remove the character to the right side of the cursor.

And also delete a specific highlighted bar.

Status light – indicate whether the Num Lock, Caps Lock and Scroll Lock

features are on or off.

Spacebar key – used to insert a blank space.

Enter Key – tells the computer to carry out a task.

Arrow Keys – lets you move the cursor around the screen.

Numeric Keypad – when the Num Lock is on, you can use the number keys

(0-9) to enter numbers.

Mouse

A mouse is a handheld pointing that lets you select and move items on your screen.

Casing

A casing contains all the major components of a computer system. This part usually carries all the supplies needed to run a system. The case supports the power supply, the motherboard, and the cards, drives, and internal cables. The case also houses the drive that comes with 5 ¼ and 3 ½.

The case will also provide some bays that open to the front of the computer and others that are accessible only from the interior of the case. The external bays are for floppy drives. CD-removable disk, tapes, and any other devices that use removable media, while the internal bays are for hard disks.

Power Supply

A power supply charges the alternating current (AC) that comes from the outlet to the direct current (DC) at the voltage require direct current at 24V, 12V, 5V, and 3V whereas in the United States, typical wall outlets provide alternating current at 110V. The power supply is visible from the back of many systems because it contains the power cord receptacle and the cooling fan. Power supplies, often referred to as “switching power supplies”, use switcher technology to convert the AC input to lower DC voltages.

Sockets and slots

Name Pins Layout Chips

Socket 7 321 SPGA Pentium 75-266,MMX,OD,x86,K-5,K-6

Socket 8 387 Dual-pattern SPGA Pentium Pro

Socket 370 370 SPGA Celeron PGA, Pentium III PGA (PGA) 370

Socket A 452 PGA Socket Duron, Athlon PGA (Socket 462)

Slot 1 242 Edge connector Pentium II, Celeron SEP,Pentium III SEC (SC242)

Slot A 242 Edge connector Athlon SEC

Slot 2 330 Edge connector Pentium II, Xeon, Pentium III Xeon (SC330)

Motherboard

The main circuit board of a microcomputer. The motherboard contains the connectors for attaching additional boards. Typically, the motherboard contains the CPU, BIOS, memory, mass storage interfaces, serial and parallel ports, expansion slots, and all the controllers required to control standard peripheral devices, such as the display screen, keyboard, and disk drive. Collectively, all these chips that reside on the motherboard are known as the motherboard’s chipset.

Expansion Slot

An expansion slot is a socket where you plug in an expansion card. Then most of the expansion cards are accessible from the back of a computer. An expansion card is also usually called expansion board.

Expansion Card

These expansion cards contain ports where you can plug speakers into a sound card to hear the sound generated by the computer.

Types of Expansion Card

A computer usually comes with one or more expansion cards.

A Video Card generated the images displayed on the monitor.

A Sound Card let’s a computer play and record high-quality sound.

A Modem Card let’s computer exchange information through telephone lines.

A LAN Card or usually called the Network Interface card lets connected computer share information and equipment.

Memory

Memory, also called Random Access Memory (RAM), temporarily stores data inside a computer.

Memory works like a blackboard that is constantly overwritten with new data. That data stored in memory disappears when you turn off the computer.

Memory Size

The amount of memory determines the number of programs a computer can run at once and how fast programs will operate.

Memory is measured in bytes. You should have a computer with at least 32MB of memory, but 64MB is recommended. You can improve the performance of a computer by adding more memory. The type of memory depends on how you want to build your system. 8MB – 1GB of actual memory you could inset in you motherboard.

Classes of Memory Chips:

· DRAM or Dynamic RAM is a type of memory chip that makes up the main memory in many computer systems.

· EDO RAM or Extended Data Out makes a system fast.

· SDRAM or Synchronous is much faster that the convenient EDO RAM and a standard in all Pentium II system.

· DDR SDRAM (Double Data Rate Synchronous Dynamic Random Access Memory) Allow 1.066 gigabytes transfer rates on a motherboard’s 66MHz bus, available in 1999.

· RDRAM (Rambus Dynamic Random Access Memory) Can operate at motherboard bus clocks of 133 MHz. Can transfer data at 533Mb/s per channel. Supports up to four channels for a total speed of 2132Mb/s access speed of 2ns.

Memory Module

A memory module is a circuit board that holds memory chips. A single-in-line memory module (SIMM) holds up to nine memory chips. New computers also accept Dual-in-line memory modules (DIMM), which can hold up to 18 memory chips. You can add more memory to a computer by inserting additional memory modules.

Memory Module Socket

A memory module socket is a socket on the motherboard where you plug into a memory module.

SIMM – is defined as Single Inline Memory Module. It uses both sides of each contact

together. Each contact gives a single signal.

DIMM – is a Dual Inline Memory Module. It uses the opposite sides of each contact for

separate signals.

SIPP – (Single Inline Pin Package). A less common type of memory module. The main

difference here is that the contacts are distinct pins, which fit into holes, as opposed to the row of contacts that fit into a slot.

Hard Disk

The hard drive or hard disk is the primary device that a computer uses to store information.

Most computers have one hard drive, located inside the computer case. If a computer has one hard drive, it is called drive C. If a computer has additional hard drives, they are called drives D, E, F, and so on.

The hard drive light is on when the computer is using the hard drive. The hard drive magnetically stores data on a stack of rotating disks, called platters. A hard drive has several read/write heads that read and record data on the disk.

Hard Drive Contents

Program files are usually installed on your hard drive, you could cope and delete files inside your hard drive.

Data files stores your data inside the hard drive such as documents, spreadsheets and graphics.

Store Files

Save files are used every time you are creating document. The computer stores it first in the memory before sending it to the hard drive. If you want to store document for future use, you must save the document will be lost when there is a power failure or you accidentally turn off the computer.

Organize files if like a filing cabinet, a hard drive uses folders or directories to organize information.

Capacity

The amount of information a hard drive can store is measured in bytes. A hard drive with a capacity of 3 to 4 GB will suit most home and business users. Purchase the largest hard drive you can afford. New programs and data will quickly fill a hard drive.

Speed

The speed at which the rotating disks in the hard drive, called platters, spin is measured in Revolutions Per Minute (RPM).

Floppy Disk

Secondary device use to stores and retrieves information on floppy disks. The 3.5 inches floppy drive allows you to store up to 1.44 megs of information on the floppy disk. The 5.25 inches floppy drive allows you to store up to 1.2 megs of information on the floppy disk. You can also download files to either of these drives as well as upload files onto your hard drive or the C:\> drive.

CD-ROM Drive

A device that read information stored in compact disks. Your CD-ROM Drive, very much like the floppy drives, allows you to install programs and files onto your computer’s hard drive, play music CD, games, etc… The CD-ROM drive is much quicker than both of the floppy drives and can hold more information than the floppy disks.

CPU (Central Processing Unit)

Is actual brain of a computer, it is responsible for processing instructions and carrying out user’s commands. The CPU processes instructions, performs large amount of calculations and manages the flow of information through a computer system. The CPU performs millions of Calculations every second. The CPU is also called the microprocessor or processor.

Universal Serial Bus

The Universal Serial Bus divides the available bandwidth into frames, and the host controls the frames. Frames contain 1,500 bytes, and a new frame starts every millisecond.

DOS COMMANDS

DIR – displays all files in directory or subdirectory

CLS – clears the screen

CHDIR/CD – Change Directory, changes or displays the working directory

COPY – copies the specified files

DATE – displays or sets the current dates

TIME – displays or sets the current time

DEL – deletes the specified file(s) = ERASE

EXIT – exits the current command processor and returns to the previous level MKDIR/MD – make directory

PATH = sets a command search path (PATH=) in the environment

PROMPT – changes the MS-DOS command prompt (PROMPT=) in the environment

RENAME/REN – renames first file as second file.

RMDIR/RD – remove directory removes an empty directory

VER – displays the MS-DOS version number

VERIFY - verifies all writes to a disk during COPY OF XCOPY

VOL – displays the disk volume label

FDISK – prepares (partitions) hard disks for FORMAT

FORMAT – format a disk with an empty, file allocation table (FAT) ready to receive files

XCOPY – copies files and subdirectories

System Components

A modern PC is both simple and complicated. It is simple in the sense that over the years, many of the components used to construct a system have become integrated with other components into fewer actual parts. It is complicated in the sense that each part in a modern system performs many more functions than did the same types of parts in older systems.

Here are the components and peripherals necessary to assemble a basic modern PC system:

◊ Motherboard ◊ Keyboard

◊ Processor ◊ Mouse

◊ Memory (RAM) ◊ Video card

◊ Case/Chassis ◊ Monitor (display)

◊ Power Supply ◊ Sound Card

◊ Floppy Drive ◊ Speakers

◊ Hard Disk ◊ Modem

◊ CD-ROM,CD-RW, or DVD-ROM Drive

ASSEMBLING A PC SYSTEM

This module will enable you to:

1. Know what is inside and outside your PC that makes it work.

§ Parts and devices, their functions and locations

§ Components, their functions and location

2. Understanding the process that takes place in you PC

§ Data entry, storage, retrieval, and display

§ Data signal and translation

3. Connect the parts and devices that will make your PC functional

After going through this portion successfully, you should be able to start your work on your PC.

How does a PC work?

Have you ever wanted to flip open your computer case to see physically what’s inside it? To satisfy your curiosity, we’ve lifted the top off a computer so you can see and describe its major parts. Knowing the parts that make up a computer, as well as their locations and functions will ease your assembling tasks. Almost all signals, information, and functions travel through your computer’s microprocessor, which is the brain of your computer. This component also is called the central processing unit, because this is where most of the processing takes place. The microprocessor depends on other components to perform many specialized functions. For instance, it needs random access memory (RAM) as a temporarily storage space to hold the programs and files with which it is working currently.

The microprocessor also needs a hard drive or diskettes for permanent data storage, a keyboard for data entry, and a monitor to display the data. Other extras, such as modems and sound cards, let the computer perform supplemental tasks such as exchanging information over telephone lines or playing music.

Steps in Installing a PC system

Motherboard

The motherboard is the main circuit board of the Microcomputer. The Motherboard contains the connectors for attaching additional boards.

Typically, the motherboard contains the CPU, BIOS, memory, mass storage interfaces, serials and parallel ports, expansion slots, and all the controllers required to standard peripheral devices, such as the display screen, keyboard, and disk drive.

Collectively all this chips that reside on the motherboard are known as the Motherboard Chipset. Replacing the Motherboard on your PC, is one of the more challenging upgrades you can undertake, but it also will be one of the most rewarding in terms of computing performance and personal satisfactions.

The preliminaries

The motherboard also known as the “system board” or “main board”, is a circuitry board embedded with transistors, sockets, slots, and integrated circuit or “chips”. It is attached to the computer case with screws and standoff posts.

The microprocessor, single inline memory modules (SIMMs, or RAM chips), expansions cards (such as internal fax/modems), keyboard, and mouse all plug into sockets or slots on the motherboard. Some motherboards use built-in circuits to control the diskette drive and hard drive. Others use built-in circuitry to convert data into the images displayed on the computer’s monitor.

Most old model PCs doesn’t use these “onboard controllers”, or “expansion cards” that you insert into the motherboard’s expansion bus perform these functions. Usually, you can tell by opening your case whether these circuits are built into the motherboard or onto expansion cards. If not, refer to your PC manual.

Ribbon cables (flat, wide cables) and wires attach the motherboard to other devices connected to the case, including the power supply, disk drives and a small speaker. Some carry data or power to other parts of the PC.

Understanding Your Motherboard – Internal

Understanding your motherboard is about pointing out what the bits of your motherboard actually do, if you are not used to building or upgrading your own machine you will want to know the ins and outs of the motherboard. The motherboard is a very important piece of equipment in your PC as it is connected to everything. Anything of major importance is plugged straight into the board. Some things on a motherboard meant to be changed and altered to suit your own will try to give you a brief bit of history if there is any on each of these parts and some specifications.

We will start on the Internal connectors and ports and then move on to the External ones.

ISA (Industry Standard Architecture) slot

The ISA slot in an old type of connector for internal peripherals such as modems and network cards. ISA is a system bus running a slot slower than the PCI and AGP bus speeds. ISA runs at only 8 Mhz maximum, although some systems do allow this to be over clocked to 12Mhz. Still very slow and as new motherboards are introduced the ISA slot is being left behind. It is hard to find components for the ISA bus now, if you are looking for ISA components then second hand stores are the best place to look, Network Card, Sound Card and Modems can still be found. ISA is a 16-bit bus, allowing for 16 bits of data to e-sent simultaneously.

PCI (Peripheral Component Interconnect) slot

Intel developed the PCI bus, however, this local bus is not only for Intel processors, and you will find it very difficult to find a motherboard without a PCI slot on it. You will find that to get a number of PCI slots from 1 up to about 6. The PCI bus runs at 33Mhz and normally 32 bits. The PCI bus was that must one to fully support plug and play, where IRQ’s and other resources are set up by the OS and there are no need to alter jumpers and on the hardware. The PCI bus supports a wide range of peripherals from sound cards to DVD decoders and graphics accelerators. PCI is now the standard for internal peripherals except for graphics cards, which have now moved over to the faster AGP port.

AGP (Accelerated Graphics Port)

The AGP was designed specifically for video cards. AGP was really forced in to the computer world, as graphics cards required more and more bandwidth. AGP provided not only a faster bus speed (66MHz 2x – 266MHz 4x effectively) but also allowed fast access to the main memory allowing for greater storage space in the memory for textures. Unlike the ISA and PCI local buses the AGP is a port and not a bus. This is because it is not expandable, it only involves the two devices the graphics card and the CPU AGP still uses 32 bits but is based on the PCI 2.1 standard that allowed 66MHz-transfer rate instead of 33MHz.

ATX Power connector

The standard ATX power connector, the cable for this will be coming from the PSU, a clip is normally provided to make sure you get them in the correct order. As a tip, don’t try to push too hard if its stuck, check to see that it is in the correct way. I have seen plenty of power connectors, where the pins have pushed out some of the connectors, these can be difficult to get back into place, so its best to be careful.

Chipset (with heat sink)

The motherboard chipset can be described as what sets it apart from other boards in its category. Different chipsets contain different features and components. A chipset is a number of integrated circuits built onto the board to provide specific functions; one part of the chipset may be an onboard component such as a modem or sound chip. Other parts may be used to control the CPU functions. Most chipsets support more that one type of CPU such as socket 7, which supports the Pentium, Cyrix 686, Cyrix MII, AMD K6 and K6-2. There are certain restrictions though to what type of processor a chipset can handle because of the logic that the CPU uses to access the memory and its cache etc. chipsets have started to put head sink on the main parts of the chipsets to disperse some of the heat.

CPU (Central Processing Unit)

All the CPU “socket look very similar, however they are different in the way they have different amount of pins and in different layouts. Because of this getting the right one is essential. A socket 7 CPU and a socket a CPU as well as a socket 370 CPU all look the same.

DIMM (Double Inline Memory Module) slots

These are by far the most common memory slots at the moment, the other are SIMM (Single Inline Memory Module) and RIMM (Rambus Inline Memory Module). DIMM’s are used to virtually every board except for those on P4 boards, which predominantly use RIMM’s. The standard for DIMM’s are PC133. PC100 is now memory running at 100MHz and PC100 at 133MHz. Being introduced now is DDRRAM that effectively doubles the data being sent in one cycle by utilizing the trough and the peaks of the signal.

Understanding your Motherboard – External

The motherboard also has external connectors for devices such as keyboards mouse and printers. We will take a quick look at these connectors and show which is which. Although it is difficult to plug pieces in the incorrect slot due to there shape and size differences, it help to have the knowledge of what you are going rather than just fitting the one that fits. Again you can click on the numbers on the image to take you to the section you require.

ATX boards have 2 PS/w connectors, one for the mouse and one for the keyboard. They are the same size the same shape but a different color. This is because the Mouse and Keyboard connectors are not interchangeable. Plugging the keyboard in to the mouse connector and vice versa will make them both useless. The usual ways for these to be plugged in is the mouse into the Green connector and the Keyboard into the Purple connector.

ATX – is a development of the Baby AT specification with the motherboard rotated 90 degrees in the chassis.

USB is getting more and more popular for external components. You can buy external USB hard disks now in the market. The big hype about USB is that you can change the devices on the USB without switching the power off the computer. Is you have mouse and Scanner and plug in your game controller, the system would be recognize the change and let you use the controller straight away. You will normally get 2 USB ports with an option to add an extra 2 via a cable.

Parallel Ports

The parallel port is mainly used for scanners and printers, and is associated with LPT1. Parallel ports send data in parallel. More than one bit at a time. If the channel were 8 bits wide then a parallel port would send 8 bits at a time.

IDE connector

The connectors to whom you will insert an IDE cable (supplied with motherboard) IDE cables connect devices such as hard disks, CD Drives and DVD Drives. The current 3 standards of IDE devices are ATA 33/66/100, the numbers specify the amount of data in Mb/s in a max burst situation. In reality there is not much change of getting sustain data rate of this magnitude. Both the connectors and devices are backwards compatible with each other, however they will only run at the slowest rated speed between them. All IDE cables will come with a red line down one side, this red line is to show which way it should be plugged in. The red line should always connect to pin one of the IDE port. Checking your motherboard documentation should show you which end is pin one. In some cases it will be written on the board itself. In the case of ATA 66/100 there is a certain order that you plug devices in, the cable is color coded to help you get them in the correct order.

Floppy Drive connector

Simpler than the IDE connector you only have to remember to get red line to pin 1 of the connector and the red line to pin 1 on the floppy drive. this port is only to be used with floppy drives.

Motherboard Battery

The battery gives the board a small amount of power in order to store some vital data on your machine when the power is off. Data stored is that like the time and date so you don’t have to reset all the data every time you boot the machine up. Motherboard batteries are usually long lasting Lithium batteries. Removing this can rest all the data on your machine including the BIOS settings, however not replacing this correctly can lead to irreparable damage to the motherboard. Only remove the battery if it is dead or if you can’t have access any other way to resetting the data on your machine by use of the clear CMOS jumper or something similar.

BIOS (Basic Input Output System) chip

The BIOS holds the most important data for your machine, if configured incorrectly it could cause your computer not to boot correctly or not at all. The BIOS also informs the PC what the motherboard supports in terms that the CPU is off. That is why when a new CPU is introduced that physically fits into a slot or socket you may need a BIOS update to support it. The main reason for this is that different CPU’s use different logic and methods and so the BIOS has to understand certain instructions from the CPU to recognize it.

Game Port

The game port is really just a serial port normally found on a sound card as the picture above has onboard sound in order to show you everything an ATX motherboard can have on it, the game port is above the sound connectors. Game ports and joysticks plug into the game port. The game port is a female connector and larger than that of the standard COM port.

Sound Card Connectors

The sound card that is built into the board has three connectors, these are: speaker out, this is your main output for your computer speakers, depending on you sound chip you may or may not need powered speakers. Check with the motherboard manual for this. Then you will have the Line in is for external sources of audio that you want to hear through you computer or possibly record, i.e., from you Hi-Fi. The last of the 3 is the Mic port. This is for the microphone can be used to add sound to recording or just to play through your speakers system.

Display Connector

This motherboard also have onboard graphics, if this is the case with your motherboard then you will have this connector or your motherboard. The display connector is also female (meaning the pins will be on the end of the monitor cable). If you have a standard graphics card then this connector will be on the back of your graphics card.

The COM port is used for peripherals such as mice and modems, becoming less popular now though as USN and PS/2 have taken over. Motherboards seem to only have the 1 COM port now in favor of more USB ports.

Creating Boot disk for a system

A boot disk contains all the necessary operating system files your computer needs to get started. Boot disks can be tremendously important for many different applications and frankly, no computer user should be without one.

For example, if your hard drive fails, or if you have the misfortune of contracting a computer virus that attacks your hard disk’s master boot record (as many of them do), system files get accidentally deleted or otherwise corrupted, a boot floppy will be your savior.

In addition, if your ever want to reformat your hard disk or reinstall Windows 95 or Windows 98, for that matter form the CD, you’ll also need to have a boot disk. Some older DOS games also work better if you boot your computer from a startup disk.

In recognition of this importance, such as Scandisk.exe, Fdisk.exe and Microsoft made the process of creating Format.com a basic Windows 98 boot disk very easy. All you have to do is:

· Click the Start bottom, go up to Settings, select Control Panel from the list of available choices and when the Control Panel window opens.

· Just double click on Add/Remove Programs

· Once that’s open, click on the Startup Disk tab and click on Create Disk.

You’ll be prompted to insert the Windows 98 CD into your CDROM drive (in most cases) or to put a floppy disk into the floppy drive.

· After a minute or two, you’ll have a disk that includes all the critical files necessary to start your computer and “see” your hard disk.

The basis boot disk also includes important disk utilities.

Scandisk – error is correctly by this program and provides additional information on how much data are being used within your system.

Fdisk – is used to activate an existing drive

Format – is used for cleaning up and making the system bootable.

This section discusses how to remove and install these components for several different types of systems. With regard to assembly and disassembly, it is best to consider each system by the type of case that the system uses. All systems that have AT-type cases, for example, are assembled and disassembled in much the same manner. Tower cases basically are AT-type cases turned sideways, sot the same instructions apply to those cases as well. Most slime line and XT style case are similar; these systems are assembled and disassembled in much the same way.

The following section lists disassembled and reassemble instructions for several case types, including those for all standard IBM-compatible systems.

System Disassembly

Disassembling most systems normally requires only a few basic tools; a ¼ inch nut driver or Phillips-head screwdriver for the external screws that hold the cover in place, and a 3/16 – inch nut driver or Phillips-head screwdriver for all the other screws. Needle-nose pliers can also help in removing motherboard standoffs, jumpers, and stubborn cable connectors.

An anti-static mat is useful for placing components on while they are out of the system chassis to protect them from static. If you don’t have a mat, them any nonmetallic static free surface as a work area.

Removing the Cover

To remove the case cover, follow these steps:

1. Power off the system. Disconnect all of the cables at the back of the case, including the power cable.

2. Examine your case to determine how to remove the cover. Remove the screws holding the case cover on the chassis. These are normally around the rim of the cover and are normally in the rear; however, in some cases, the screws are behind the front plastic faceplate or bevel.

3. Once the screws are removed, grasp the cover and slide or lift it off. Some covers slide toward the back and some to the front; some lift straight up.

4. Now is a good time to connect the wrist strap or anti-static mat if you have one. Wear the wrist strap on one wrist and clip the wire end to a metal part of the case. Clip the wire from the mat to the case as well. This will keep you and the equipment at the same electrical potential and prevent any damage due to static electricity.

Removing Adapter Boards

To remove all the adapter boards from the system unit, first remove the system unit cover, as described in the previous section. Then proceed as follows for each adapter.

1. Note which slots each adapter is in; if possible, make a diagram or drawing.

2. Remove the screw that holds the adapter in place.

3. Note the positions of any cables that are plugged into the adapter before you remove them. In a correctly wired system, the colored stripe on one side of the ribbon cable always denotes pin 1. some connectors have keys that enable them to be inserted only the correct way.

4. Remove the adapter by lifting with even force at both ends.

5. Note the positions of any jumpers or switches on the adapter, especially when documentation for the adapter is not available. Even when documentation is available, manufacturers often use undocumented jumpers and switches for special purposes, such as testing or unique configuration. It’s a good idea to know the existing settings, in case they are disturbed later.

Removing Disk Drivers

Removing drives is very easy. The procedure is similar for all types of drives, such as floppy, hard disk, CD-ROM, and even tape drives. Special rails or brackets are attached to the sides of the drives, and the drives slide into the system-unit chassis on these rails or brackets. The chassis has guide tracks for the rails, which enable you to remove the drive from the front of the unit without having to access the side to remove any mounting screws. The rails normally are made of plastic or fiberglass, but they can be made of metal in some systems. It should be noted that any brackets or rails should remain attached to the drive while you are removing or installing it.

Always back up hard disks completely before removing disks from the system. A backup is important because the possibility always exists that data will be lost or the drive damaged by rough handling.

To remove the drives, first remove the cover. Then proceed as follows.

1. Depending on the specific case design, drives may be mounted using special brackets or rails. Locate the screws holding each drive bracket or drive assembly in the case and remove them. Some drives will slide out on rails, or be removed with the bracketry still attached to the drive itself.

2. Disconnect from the drives the power cables, data cables, and any ground wires if present. In a correctly wired system, the colored stripe on one side of the ribbon cable always denotes pin 1. The power connector is shaped so that it can be inserted only the correct way.

3. Slide the drive completely out of the unit.

Removing the Power Supply

The power supply is mounted in the system unit with several (normally four) screws in the rear and sometimes-interlocking tabs on the bottom. Removing the power supply may require that you slide the disk drives forward for clearance when you remove the supply. To remove the power supply, first remove the cover then proceed as follows:

1. Remove the power supply retaining screws from the rear of the system unit chassis.

2. Disconnect the cables from the power supply to the motherboard, and then disconnect the power cables from the power supply to the disk drive. Always grasp the connectors themselves never pull on the wires.

3. Lift the power supply out of the chassis.

Removing the Motherboard

After all adapter cards are removed from the unit, you can remove the motherboard. The motherboard is normally held in place by several screws, and may also use plastic standoffs that elevate the board from the metal chassis so that the bottom of the board does not touch the chassis and cause a short.

You should not separate the standoffs from the motherboard before removing it from the chassis, instead, remove the board and the standoffs as a unit. The standoffs normally slide into slots in the chassis. When you reinstall the motherboard, make sure that the standoffs are located in their slots properly. If one or more standoffs do not engage the chassis properly, you may crack the motherboard when you tighten the screws or install adapter cards.

To remove the motherboard, first remove all adapter boards from the system unit ad described earlier. Then proceed as follows:

1. If the motherboard had onboard floppy, hard disk, serial or parallel ports, document those cable connectors and mark them before disconnecting them.

2. There are numerous small wires that go from the front panel on the case to the motherboard. Before disconnecting them, document the wire connections to the motherboard, and use some masking tape or some kind of label to mark the small wire connectors as you take them off the motherboard. Marking these wires will save you a lot of time later during the installation.

3. If there is an active heat sink in the CPU which incorporate a fan, unplug the power lead to the CPU fan.

4. If you have not already removed the power supply, document how the power supply cables are plugged into the motherboard, and disconnect the power supply connections to the board.

5. Locate and remove the motherboard retaining screws, making sure you save any plastic washers that might be used.

6. Slide the motherboard away from the power supply about a half-inch, until the standoffs have disengaged from their mounting slots.

7. Lift the motherboard up and out of the chassis. Place it on a static free surface, such as an anti-static mat.

8. Remove the CPU and any memory modules you want to reuse later.

Removing SIMM or DIMMs

One benefit of using single or dual inline memory modules (SIMMs or DIMMs) is that they’re easy to remove or install. When you remove memory modules, remember that because of physical interference, you must remove the memory-module package that is closest to the disk drive bus-adapter slot before you remove the package that is closest to the edge of the motherboard. This procedure describes removing a SIMM device; note that a DIMM is also removed in exactly the same way. The only difference is that a DIMM is slightly longer and has more contacts than a SIMM device.

To remove a SIMM (or DIMM) properly, follow this procedure.

1. Gently pull the tabs on each side of the SIMM or DIMM socket outward.

2. Rotate or pull the SIMM or DIMM up and out of the socket.

CAUTION: Be careful not to damage the connector. If you damage the motherboard memory connector, you could be looking at an expensive repair. Never force the module; it should come out easily. If it doesn’t you are doing something wrong.

Basic Troubleshooting Technique

Objectives:

1. Understand the machine and your ability to proper troubleshoot computer circuitry.

2. Provide you with the analytical tools and tips needed to localize a problem.

3. Identify the failed part, and to make the correct repair.

4. Discuss the safety precautions during the troubleshooting and repairing.

Introduction to Troubleshooting

PC problems will occur, but you need to know to confirm that a failure symptom is really a failure and not just an operator error or a software bug. Software incompatibility can lead one suspect a disk drive problem, even when it isn’t easy to blame the computer, but the machine may not be a fault.

TROUBLESHOOT – To systematically locate a computer hardware or electrical/electronic failure. Software failures are found to be systematic debugging.

FAULTS – is any physical condition that causes an incorrect output when a circuit is exercised to perform a function.

STATIC FAILURE OR FAULTS – include the stuck at problems associated with open or shorted data paths in circuitry.

SHORTS – can be described as electrical conduction in the wrong place and caused by a mechanical failure in a device or be solder bridge during repair.

OPENS – are characterized by a lack of electrical conduction when it should be present.

DYNAMIC FAILURES – include time-dependent error, such as the loss of the signal quality, which causes a circuits output to reach steady state too late to be properly used by another part of the system.

LOGIC TROUBLESHOOTING – the most effective way to locate a failure in a PC is to approach the problem just as the machine operates logically.

There are typically two ways to analyze electronic circuit failure.

1. Classical troubleshooting – incorporating the localizing and isolating of failures, using deductive reasoning and mental intuition.

2. Brute force troubleshooting – utilizing flowcharts and the replacement of all suspected components.

BASIC TROUBLESHOOTING

Solving computer problems requires the application of deductive technique called “troubleshooting”. In general there are some optimum steps that you can follow to successfully troubleshooting and repair a computer.

CAUTION: Modifying or removing components from the circuit boards in your system may void the manufacturer’s warranties.

CAUTION: Discharge any static electricity present on your body before troubleshooting or repairing any part of the computer system.

WARNING: High voltages are present inside the power supplies and display terminals. Unless you are trained in the repair of these units, you should not try to troubleshoot, or in any way open and work inside either the power.

BASIC STEPS IN TROUBLESHOOTING

A. Visual Inspection

There are several specific steps you should take when troubleshooting an IBM PC system and compatible.

§ Search out the entire symptom the clues that point toward the location of the failure.

§ Make a visual and operational check of everything that is normally active during the operation of the failing function.

§ Look for loose or incorrectly connected cable and power cord, switches that are incorrectly set, disk drive doors inadvertently left open, de-energized wall socket, and bad disk.

§ Look for anything that appears out of place.

B. Diagnose to a section

Once symptom analysis completed, narrow the failure down to a single section.

§ Turn the computer off.

§ Check every component where exactly the failed components.

§ Retest if the problem remains.

C. Localize to a Stage

D. Isolate to a failed part

HOW TO LOCALIZE FAILURE

There are two ways to localize failures and determine which computer part has malfunctioned: The hardware approach and the software approach.

The Hardware Approach

In this approach, physical tests are conducted on the system and its component to isolate, localize, and identify failure sources. For those problems that are not easy/to identify, let’s refer these guidelines for success.

§ Don’t panic

§ Observe the conditions

§ Use you senses

§ Retry

§ Document

§ Assume one trouble

§ Use correct technical reference data

§ Diagnose to a section (fault identification)

§ Localize to a stage (fault localization)

§ Isolate to a failed part (fault isolation)

§ Use correct equipment to aid in the repair

§ Test and verify

The Software Approach

This troubleshooting method used widely by most PC technicians and system self-repair users, as long as the disk drive will boot properly.

Diagnostic and Special test
Memory Test

Repairs can generate failure

Overzealous or under trained personnel, and those novice technicians who are in a hurry or do not understood the system being analyzed, can introduce more trouble than they correct.

Ø Bent or broken pins

Ø Electro Static Discharge (ESD)

Ø Improper soldering/desoldering

Ø Improper cable Hook-up

Ø Noise Interference

Ø Liquid fry

Specific Troubleshooting and Repair of IBM PC and Compatibles

This chapter covers the detailed analysis of failures associated with the IBM PC compatibles. The chapter is divided into six parts as follows:

Start up Problems
Run Problems
Disk Drive
Hard Disk problems
Keyboard/Mouse problem
Display problems
Other I/O problems

START UP PROBLEMS

Four types of error indicator can occur during initialization or start-up process beep indicators from the built-in speaker, system error-code displays. I/O code displays and other error displays. This indications will assist is isolating failure to a module, sub-unit, or peripheral.

POST-AUDIO ERROR CODES

Usually are audio consisting of a number of beeps that identify the fault components:

_________________________________________________________________

Audible Code (Sound) Problems (Fault Domain)

1-short beep Normal POST * system OK

2-short beeps POST error codes

No beeps, nothing happens Power supply, system board

Continuous beeps Power supply, system board, and memory module

Repeating short beeps Power supply, system board, & memory module

1-long, 1-short beeps System board

1-long, 2-short beeps Display adapter (MDA, CGA)

1-long, 3-short beeps Check EGA adapter

3-long beeps 270 –keyboard card

* POST – Power On Self Test

PC ERROR CODES

CODE DESCRIPTION

1XX System board error

2XX Memory (RAM errors)

3XX Keyboard errors

4XX MDA errors

5XX CGA errors

6XX Disk Drive/Controller Drive error

7XX Math-Coprocessor error

9XX Parallel printer adapter errors

RUN PROBLEMS

This section covers those problems you might encounter while your system running. For example you attempt to do something and get a response entirely different from what you expected.

1. While running, the computer locks up. There is no keyboard response.

Hints: This problem can be caused by a failure in the non-maskable interrupt circuitry.

2. Power turns off after system runs for a while.

Hints: This problem occurs mostly in the power supply circuitry.

POWER SUPPPLY FAILURES

Two types of power supply failure can occur: Hard failure and short-term power fluctuations. A hard failure either prevents any output to one or more power pins on the system board. Power surges or suppression failures occur when a power supply puts too much or little voltage.

Warning: WORKING ON POWER SUPPLY CAN BE DANGEROUS.

SYSTEM BOARD PROBLEMS

A system board problem or support circuitry malfunctioning will usually result catastrophic failure that can either be detected by POST diagnostic at boot-up or will prevent the boot-up from completing. If the power supply seems to work (the fan is running and the screen “blinks” when system power is applied), the failure is likely on the system board.

Floppy disk Drives: Maintenance

you use one of the simple head cleaning kits available from computer-or-office supply stores.
setting the floppy drive speed adjustment.
aligning floppy disk drive.

HARD DISK DRIVE TROUBLESHOOTING & REPAIR

Most of the time, a seek failure indicates that the drive is not responding to the controller. This failure is usually caused by one of the following problems.

ü Incorrect drive-type setting

ü Loose, damaged, or backward data cable

ü Temperature-induced mis-tracking

Hard Disk and controller Diagnostic Error Codes:

17XX – codes apply to ST-506A112 problem with HD, controller, & cables.

104XX – errors apply to ESDI driver controllers.

210XX – errors apply to SCSI drives and host adapters.

KEYBOARD TROUBLESHOOTING & REPAIR

Keyboard failures can be frustrating, especially when a key works right part of the time, but not all of the time. Most common cause for keyboard failure.

§ Heavy-fingered user

§ Liquid fry or liquid spill

§ By the electronic components

§ Damaged cable & connectors

§ Dust and dirt

DISPLAY PROBLEM

Most displays problems are caused by the following:

Bad connection
Video card failure
Power supply hi-voltage failure
Video display circuitry failure

Short inside CRT
Open or disconnected wiring inside CRT
Screen edge won’t display
Bright “bloomy” letters; poor intensity control
No picture – no brightness
Marginal performance

MOUSE TROUBLESHOOTING

In the following does not function properly arises, please check the following before calling your dealer.

1. Check that the mouse connection is firmly plugged into the serial port.

2. Make sure that the correct serial port is chosen. If necessary, move the Mouse to another port.

3. Check the mouse cable to see if it broken or has any sharp bends.

4. If the mouse pointer appears on the screen but does not move, make sure the correct Mouse driver is installed.

5. If the cursor moves irregularly across the screen, clean the Mouse roller.

6. If the mouse pointer moves erratically or jumps on the screen, make sure that mode (2 or 3 button) is selected.

Recommended Troubleshooting & Repairing Equipment

If you’re planning to tackle failures that usually require Service Center support you can minimize your investment costs and yet optimize your chances of success by carefully selecting your equipment and tools.

Below is a list for typical troubleshooting and repair equipment.

Screwdriver
Soldering Iron (25-60 Watts with 1/16-1/8 inch tip)
Pliers (4 ½” short-nose 5 ¼” long-nose)
DMM (3 ½” digit)
Logic Probe
Logic Pulser
Current Analyzer
Logic clip
Oscilloscope
Logic Analyzer

Additionally, the following items are helpful with basic computer and electronics repair.

Inch long tweezers (for gripping removing small parts)
IC removal tool (a U shaped handle with fingers to hook under chips)
1-inch wide brush (for dusting of parts)
Can pressurized air with nozzle (for blowing dust off parts and dirt of small places, such as keyboard)
A small amount of electrical/electronic solder labeled 60/40 for tin-to-lead content ratio.
A pair of wire strippers and pair of small electronic-wire cutters.

There are possible ways to optimize the operational life of your computer system.

1. Buy a highly reliable computer with good-performance track record.

2. But good on-site repair contact.

3. Buy second identical computer to use as a backup during the repair of the first.

4. Become a knowledgeable repair technician yourself.

Developing a Preventive Maintenance

Preventive Maintenance is the key to obtaining years of trouble free service from your computer system. A properly administered preventive maintenance programs pays for itself by reducing problem behavior, data loss, components failure, and by insuring of long life for your system also increasing your system’s resale value because it will look and run better.

Two Types of Preventive Maintenance Procedures

Active Preventive Maintenance – includes steps to apply to a system that promote a longer trouble free life. This type of preventive maintenance primarily involves periodic cleaning of the system and its components.

Cleaning and lubricating all major components
Reseating chips and connections
Reformatting hard disk

Passive Preventive Maintenance – includes steps you can take protect a system from the environment includes:

Examining the operating environment
Power cycling (on/off)
Static electricity
Power-line noise
Radio-frequency interference
Dust and particles
Using power protection devices
Ensuring a clean, temperature-controlled environment
Preventing excessive vibration

Disassembling and cleaning procedure:

Reseating socketed chips
Cleaning Boards be careful with ESD (Electro Static Discharge)
Cleaning connections and contacts
Cleaning floppy disk drives
Cleaning the keyboard and mouse
Disassembly and Cleaning Tools
Contact cleaning solution
Canned Air
A small brush
Lint-free foam cleaning swabs
Anti-static wrist strap

Optional Items:

Foam type
Low volatile room temperature vulcanizing (RTV)
Silicone type lubricant
Computers vacuum cleaner

Chemicals: You can use several different type of cleaning solution.

Standard cleaning

Contact cleaners/lubricant

Dusters.

Contributors to System Failure

1. Dust and Particles

Effects:

Built-up insulates the devices and prevents the release of heat. The chips and other components to wear out faster-memory chip failures.

Overheating and an early failure.

Foreign particles can cause catastrophic problems, diskette jackets/drive increase the wear on the drive.

Countering the effect of Dust.

Use dust covers.

Keep window closed.

No smoking near your PC system.

No crumb-producing foods near your computer.

NO liquids on any equipment.

Don’t touch the surface of any floppy disk.

Clean your monitor screen with a static-reducing material.

2. Heat (Excessive Heat)

Effects:

Premature aging and failure within the components.

I/O connectors where the leads meet the chip itself.

An open-circuit failure of “thermal wipe out”.

The socketed chips to work themselves out of their sockets due to the expanding and contracting of the pins.

Disk failure; if the thin disk warps too much cause lose of information stored on that floppy.

Countering Heat Effects:

The following suggestions should help in preventing heat-related failures

Reseat the socketed chips.

Keep the cooling vent clear.

Keep your system dust-free, both inside and outside, regularly.

Keep your floppy disk in a cool, dry location.

Install an external cooling fan id system operation becomes intermittent when heated.

3. Cold

Effects:

Mechanical components have trouble functioning when temperature drops.

Mechanical sluggishness occurs with an increased possibility of erratic data storage and retrieval.

The floppy disk can become brittle, as it gets cold.

Countering the effects of Cold

Let the system warm up to room temperature (stabilized) before turning on the power.

Using a forced-air cooling system that allows for even cooling the system.

4. Noise Interference

Three types of Noise

Noise that is acoustic and affects you.

Noise that affects your computer system.

Noise that affects other electronic equipment.

1. Radio-Frequency Interference (RFI) 1Hz-10KHz

When you computer system and its cabling transit of feedback noise.

Conducted RFI – feedback noise

Radiated RFI – transmitted noise

Some ways to minimize RFI around your computer system.

Locate your computer at least 6 ft. from TV set.

Use a directional outdoor TV antenna.

Connect line filters to your TV.

Replace any antenna twin-lead wire to your TV with 75-ohm coaxial cable.

2. Electromagnetic Interference (EMI) – above 10KHz

The FCC Requirements – two categories:

Class A – are those devices use in industrial computing devices sold for use in commercial, business, and industrial environments.
Class B – are those devices use by consumers computing devices used in commercial, business and industrial applications, plus PC and their associated peripheral.

Three primary components:

Transient EMI – is the undesirable response in electrical equipment when simple on/off of a device causes a large voltage pulse, or spike to occur and go smashing through the circuitry.
Internal EMI – is the noise generated by the chips and other motherboard device.
Electrostatic Discharge (ESD) can cause a “glitch” in electronic circuits and can damage some components.

Effects of Noise Interference

Garbled screen characters, frozen cursor, and diagonal lines to appear on the screen. Also, programs can be stopped in the middle of an operation. Garbage can be read from or written to disks, paper can be jammed in the printer, memory wipe out, and it can even destroy motherboard.

Noise Counter measures

By shielding the source

Use insulating sound trapping enclosures

Use sound-absorbing foam around their computer system.

Acoustic pads placed under disk drives and printers can also reduces noise.

4. Electrostatic Discharge (ESD)

Electrostatic discharges can be any voltage. The following is a list of some of the sources of ESD glitches.

People in motion.

Overheated components.

Improper grounding.

Poorly shielded cables.

Missing covers and gaskets.

Circuit line too close.

Poor solder connections.

Low humidity.

Some Specific Solutions to ESD Problems:

Use an anti-static spray on your rugs, carpets, and computer equipment.

Install a static-free carpet in your computer area.

Place your computer system on static pads.

Install an anti-static floor mat beneath your computer chair.

Mop hard floors with an anti static solution.

Install a conductive tabletop.

Keep chips in conductive foam when not installed.

Touch a grounded metal object before touching components inside the computer.

5. Corrosion

Three type of Corrosion that can affect the PC systems:

Direct oxidation by chemical change
Atmospheric corrosion
Galvanic corrosion

Corrosion Prevention

By keeping the contact clean.

Place dust covers when it not used.

Clean the pins on some chips by reseating the chips periodically.

Use contact cleaners sprays and wipes.

6. Magnetism

If you accidentally place one of your disks in the field, the tiny pole magnets on your disk tracks can change their alignment. The moral is: Keep your diskettes, and even your information cables away from power sources.

7. Power Line Problems.

Four Types of Power-line Problems:

a. Brownouts – are those planned or sometime unplanned voltage sags.

b. Blackouts – caused by storms and lightning, is a total loss of line voltage.

c. Transients – lightning striking a power line can cause voltage spikes.

d. Noise (which discussed earlier)

Preventing Power-Line Problems:

Use power protects devices such as surge suppressors, line conditioners, backup power supply and UPS.

Disassembly and Reseating Procedures

The process of physically disassembling and reassembling systems isn’t difficult. Because of marketplace standardization, only a couple of different types and sizes of screws (with a few exceptions) are used to hold the systems together. Also, the physical arrangement of the major components is similar even among systems from different manufacturers. In addition, a typical system does not contain many components today.

DOS Error Message

DOS provides myriad error messages to indicate problems or issues that we should be aware of. Unfortunately, DOS error messages are cryptic at best, and there is precious little documentation to explain the causes of these errors (and even les help in correcting these errors). The following list provides a general index of DOS error messages, explains the potential causes of the error, and offers some practical solutions.

Note: The exact working of these errors may vary slightly between DOS versions, and not all errors may be reported in all DOS versions.

ABORT, RETRY, or FAIL

This message has several causes, but they all mean that there’s a problem with the disk(ette) DOS/Windows is trying to access. The drive is not reading a disk in the drive that you’ve instructed DOS/Windows to check. First, see that you types the correct drive letter in the command line and that the diskette is in the correct drive (if you have more than one diskette drive). Next, check that the diskette is fully inserted into the drive (label side up) and that the drive door is closed properly. Then press R to retry. This message also could mean the disk you’re using is damaged. Try the diskette in a different drive or try a different diskette.

ACCESS DENIED

You just tried to change a file that is: (1) on a write-protected diskette, (2) locked, or (3) a read-only file. Write-protected diskettes can be read but not be written to (some commercial software is write-protected). A locked file is one that can’t be altered in a common way (such as adding or deleting data, moving the file, or changing the name of the file). A read-only file is one that a programmer has added a command so that resides in read-only memory (ROM). There’s usually a good reason why you aren’t being allowed to change the file. You may need to change the attributes of the file before you’re allowed to modify it.

BAD COMMAND OR FILE NAME

DOS/Windows didn’t recognize the command you just typed or can’t find a file you referred to in the command line entry. The most likely problem is that you misspelled either the command or the file name. Another possibility is that you haven’t established the right path to a file. Recheck the location of the file and be sure to enter the path correctly when you retype the command. Finally, it may be possible that the version of DOS/Windows you’re running doesn’t recognize this command. You’ll need to see if your version has an equivalent command or update the DOS/Windows version.

BAD OF MISSING COMMAND INTERPRETER

This means DOS can’t find COMMAND.COM, and your CONFIG.SYS file doesn’t have a SHELL statement telling DOS where to look for COMMAND.COM. Your COMMAND.COM file may have been damaged or deleted, your SHELL command was removed from the CONFIG.SYS file. It may also be that the wrong version of COMMAND.COM is copied to the disk. Your hard drive may also be damaged (or infected with a virus), preventing DOS from accessing the DOS directory. Boot from an emergency bootable diskette that contains the same version of COMMAND.COM that should be on the hard drive. Then copy the file COMMAND.COM to the root directory of your hard drive and reboot. You may want to add a SHELL statement to the CONFIG.SYS file indicating the exact location of the COMMAND.COM file. You may also want to reinstall DOS (or Windows 95/98) outright.

BAD OR MISSING FILE NAME

A command in your CONFIG.SYS file is entered incorrectly. You should get this message only if you recently changed something in this file. Go back and check to be sure you typed the recent addition or change correctly. If you have not made changes to the file, the file(s) being referred to in CONFIG.SYS may be corrupt or deleted. Verify that any files referred to in the CONFIG.SYS file are present.

Note: Anytime you make a change to the files CONFIG.SYS or AUTOEXEC.BAT, make a backup copy of the original file(s) prior to making the changes.

CANNOT FIND A DEVICE FILE THAT MAY BE NEEDED TO RUN WINDOWS

The error also goes on to say, Make sure that the PATH line in your AUTOEXEC.BAT points to the directory that contains the file and that it exists on your hard disk. If the file does not exist, try running Setup to install it or remove any references in your SYSTEM.INI file. C:\directory\filename. Press a key to continue. Although this message does tell you what to do to fix the problem, it is still largely unclear. It means a given file that may or may not be necessary to run Windows isn’t where DOS thinks it should be.

The offending file is listed in the second to last sentence of the error message, and the path given is the location where DOS expected to find the file. It may be a file that was installed with an application you’ve since removed (when you remove and application from your system, a reference to a file from that program often remains in your SYSTEM.INI file). You may be able to simply press a key to continue and experience no difficulty. To be sure you don’t encounter a more serious problem, however, you’ll want to either install the offending file in the location DOS specified, point DOS to the real location of the file, or remove mention of the file from the file SYSTEM.INI file so DOS won’t try to look for it anymore.

DISK FULL

This message appears during a copy operation when the destination diskette is full. Remove some unneeded files from the diskette to make room for the full copy to fit or use another diskette to receive the additional files.

DRIVE A: DOES NOT EXIST

This message can be caused by a dirty diskette drive (the diskette cannot be read) Get a diskette drive cleaner kit and follow its instructions to clean the drive. If this doesn’t solve the problem, you may have a bad floppy disk drive or floppy disk controller.

DUPLICATE FILE NAME OR FILE(S) NOT FOUND

This message occurs when you try to use the REN command to rename a file. It means that either you’re trying to rename the file using a name that is already in use, or the file you want to rename couldn’t be found. Check your spelling and check whether the new name is already in use in the directory. Then try the REN command again, typing carefully and using a new name.

EXISTING FORMAT DIFFERS FROM THAT SPECIFIED

If you’re reformatting a disk or diskette to a different capacity, you actually want to see this message. It means you’re doing the right thing, but you’ll need to tell DOS that it’s OK to continue. The reason to reformat a diskette to a different capacity is to make it match the capacity of the drive. You can use a low capacity diskette in a high-capacity drive, but not the other way around. It’s best to match the capacity of the diskette to the maximum drive capacity.

FILE CANNOT BE COPIED ONTO ITSELF

This message probably means you forgot to give a destination location for a file you’re trying to copy. Type the COPY command again (being sure to include the destination). If you’re unsure how to use the COPY command correctly, type help copy and press enter for more information.

FILE CREATION ERROR

This means one of two things: either you’re trying to create a file with the same name as an existing file or the disk you’re using is write-protected. Check the tab on the diskette to be sure it isn’t in the write-protected position. If it isn’t, try using a different file name. If neither of these solutions works, try using another diskette with the new file name.

FILE EXISTS

You’re trying to name your new file with a file name already in use. Choose another name. If you’re unsure of which names you’ve used before, use the DIR command to check out the files in the current directory.

FILE NOT FOUND

You’ve typed a file name in a command incorrectly, the file doesn’t exist, or the file is in a location other than the one you specified. Check for accuracy and enter the command again.

FORMATTING WHILE COPYING

This is one of the DOS messages that’s more informational. It’s telling you the diskette you’re using needs to be formatted in order to hold the information you’re copying to it. You should be aware, however, that formatting a diskette takes longer while copying than if you’re just formatting it.

HELP NOT AVAILABLE FOR THIS COMMAND

Either you’ve asked for help with a command or utility program that there is no help information for in the version of DOS you’re running or you typed the command incorrectly.

INCORRECT DOS VERSION

The program you’re trying to run has found a version of COMMAND.COM other than the one it expected. You probably upgraded DOS versions at some point and now have more than one version of some DOS files on your system (and the program found an older or newer one than it wanted). You may need to reinstall DOS or Windows 95/98 to fix this problem.

INSERT SYSTEM DISK

This just means you need to insert your bootable diskette into a diskette drive, usually when installing or repartitioning a hard drive.

INSUFFICIENT DISK SPACE

You don’t have enough room on your hard disk or diskette to complete the command. Use another diskette or delete/compress some files to make more space available.

INSUFFICIENT MEMORY

This message means that you don’t have enough memory (RAM) available to complete the command. Remove any unnecessary Terminate and Stay Resident (TSR) programs and try the command again. TSRs (also known as memory-resident programs) remain loaded in memory even when they’re not running, so they can be quickly activated for specific tasks while you’re running other applications. If you’re relying on a swap file on your hard drive to emulate RAM, you may have a shortage of drive space or there may be some other problem with the swap file.

INVALID DATE/INVALID TIME

You’ve used an improper format for a date/time. To check the proper format, use the DATE/TIME command. Make note of the correct format and try again.

INVALID DIRECTORY

DOS/Windows can’t find the directory you specified. Either you typed the directory’s name incorrectly, or it doesn’t exist (at least not on the drive you specified). Check your typing and the location of the directory. It may be that it’s in a subdirectory.

INVALID DRIVE IN SEARCH PATH

This probably means that you have made a hardware change and haven’t updated that PATH command in your AUTOEXEC.BAT file to reflect the drives that are now in your computer. Update the PATH command and try again.

INVALID DRIVE SPECIFICATION

DOS/Windows can’t find the drive you tried to switch to. Either you made a typing error (asking your computer to find a drive that doesn’t exist. Or the drive you asked for is not working. If you get this message when trying to switch to your hard drive, the drive may be suffering from corrupted partition information or the drive may be defective.

INVALID FILENAME

DOS/Windows can’t find the file you’re looking for. Check the name and location of the file and try again (be sure to check your typing). Be sure to include any underscores, dashes, periods, or other valid filename characters.

INVALID PARAMETER

You’ve entered a command parameter incorrectly. A parameter is something you add to the end of a command to tell it what to operate on (also called a command-line switch). For example, in the command dir a:, the a: tells DOS you want a list of the content of the A: drive, regardless of which drive you’re currently in. Check the format of the command and re-enter it. The other possibility is that you’re using a parameter not used in the utility program you’re trying to use.

NON-SYSTEM DISK OR DISK ERROR. REPLACE AND STRIKE ANY KEY

Before computers had hard drives, the OS was stored on a diskette called the system diskette, bootable diskette, of DOS disk. That diskette was kept in the A: drive where the computer would look for it when it was started. Although OS are now on the hard drive, most computers still look at the diskette drive before checking the hard drive. If they don’t find anything in the A: drive, they check the hard drive, usually the C: drive. If they find a non-system diskette in the A: drive, you’ll get this message. The most common reason for this message is that you forgot to remove a diskette from the A: drive when you last used it. Remove the diskette and strike any key to continue. Another possibility is that you have a computer (probably an old one) that boots from a system diskette. In that case, this message means you need to put a bootable diskette in the A: drive and continue.

The last scenario is a bit more serious. If neither of the previous situations applies to you, the first step is to get a DOS system diskette and try booting the computer from it. This should get you to an A:\> prompt. At the A:\> prompt, type C: and press Enter. If you get a C:\> prompt, type C: and press Enter. Then type sys c: and press Enter again. That should replace the OS. On the other hand, if you get a message saying Invalid drive specification when you try to switch to the C: drive, your hard drive is not working properly. The drive will have to be replaced.

OUT OF MEMORY

This means a program can’t complete its task because you don’t have enough free memory. Close some other running programs and try again. If no other programs are running, you may need to add memory to your computer. Before buying more memory, you may want to try EMM386 (a driver included with DOS 6.0 that provides expanded memory) or a memory manager such as Quarterdesck’s QEMM. These tools can move some drivers and TSRs into the Upper Memory Area (UMA) and free some additional conventional memory.

PATH NOT FOUND

A path is the set of directions you give DOS/Windows to tell it how to find something. For example, the path c:\DOS\EDIT.HLP tells DOS to find the file EDIT.HLP in the DOS directory on your C: drive. If you get this message, DOS couldn’t find the path you entered. Check your typing and reenter the path carefully. If that doesn’t work, it means the path doesn’t exist.

PROCEED WITH FORMAT (Y/N)?

This message means you will lose any information that is on the diskette when you format it. Press Y to continue with the format it you’re sure you won’t lose any important information, or N to stop the process if you want to check the contents of the diskette before formatting it.

READ ERROR

DOS has found a problem with a sector of your disk. There was either damage during the formatting process or a fault in one of the sectors. Run ScanDisk (version 6.2 or newer) to find the bad spot and rescue as much data as possible. If the error occurs on a floppy diskette, you should reformat or discard the diskette.

STACK OVERFLOW – SYSTEM HALTED

Reboot your system and edit your CONFIG.SYS file so the value of stacks=is increased to 10 or more and then try again.

SYNTAX ERROR

You’ve either made a typing error in a command or you’ve used terminology DOS doesn’t recognize (or at least your version of DOS). Check your typing for accuracy and try again.

TERMINATE BATCH JOB (Y/N)?

Either you’ve interrupted a batch file in progress or the batch file is incomplete or incorrect. If you didn’t mean to interrupt the batch job, type N to let DOS return to work. If the batch file is defective, type Y to return to the DOS prompt.

THIS DISK CANNOT BE UNFORMATTED

UNFORMAT is a command that can sometimes save data if you accidentally format a disk or diskette containing data you didn’t mean to eliminate. Depending upon the type of format you performed and whether you’ve written new data to the location, UNFORMAT may not work. If it does not, try again. If you get the same message, your data is irretrievable.

TOO MANY OPEN FILES

You’ve tried to open too many files at one time. Open your CONFIG.SYS file and increase the number of files specified in the files=command. Restart your system and try again. You should now be able to have more files open at a time.

WRITE-PROTECT ERROR

You’ve tried to format a diskette that is write-protected. Remove the write protection from the disk and try again.

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Tuesday, May 29, 2012