Learning to identify computer hardware faults

The poorest people in the computer market are counting the people who have moved faulty computers. Although the Assembly Machine has her strengths compared with the brand machine, it is her critical weakness to have no good after-sales service.

Most computer faults are software faults, so there is no need to migrate the entire machine before it is determined to be a hardware fault. Even if the hardware is faulty, there is no need to move the entire machine. You only need to take the faulty parts. Therefore, it is necessary for us to understand the diagnostic and testing methods for hardware faults. In the future, when a computer fails, we do not need to move the entire machine away (of course, it is best not to fail out !).

Faults and Countermeasures

If you want to make a comprehensive analysis of computer faults, I am afraid you need to write a book, which is not easy. Software faults have been described in various newspapers and periodicals. Therefore, we will only introduce the symptoms, causes, and solutions of hardware faults.

I. Computer Startup Process

I. First, let's take a look at the computer startup process.

1. The bootstrap loader program and self-diagnosis program stored in ROM (read-only memory) are moved to Ram (random memory.

2. As bootstrap loader runs, the operating system stored in the auxiliary memory device sends system files to ram.

3. Execute the system file IO. sys and msdos. sys. "Starting windowsn98..." appears on the screen ......" .

4. If config. sys exists, run it.

5. Execute the command.com file of the system file.

6. If autoexec. Bat exists, execute it.

7. Read the Windows Initialization Files "system. ini" and "win. ini", and then read the Registry file.

8. After the startup is completed, an initial screen is displayed and the operating system is running.
In this process, the rom bios of the motherboard monitors whether the hardware is abnormal, including hardware faults, wiring, and installation of various cards. If an error occurs, the screen will show nothing and start and stop.

In this case, hardware faults may occur.

Ii. system startup sequence

1. The on-display, keyboard, and chassis lights on the PC power supply flash.

2. Detect the video card-a short video card information appears on the screen.

3. Detect memory-the memory capacity information appears on the sound screen of the beep.

4. Run bios. A brief BIOS information is displayed on the screen.

5. Check other devices-information about other devices (CPU, HDD, Mem ...).

6. Execute the OS (operating system) initialization file-Starting Windows 98.

Iii. Make a sound on the motherboard during startup. You can use this sound to determine the error.

The voice representation varies depending on the form of the motherboard.

Ami BIOS:

1 short: Memory refresh failed

2 short: Memory verification error

3 short: basic memory error

4 short: system clock error

5 short: CPU Error

6 short: Incorrect keyboard

7 short: the actual mode is incorrect.

8 short: Memory Display Error

9 short: rom bios verification error

1 long 3 short: Memory Error

Award bios:

1 short: normal startup

2 short: non-fatal error

1 long, 1 short: Display Error

1 long, 2 short: Incorrect keyboard

For other BIOS information, see BIOS error prompt.

2. obfuscated software faults

It is necessary to clearly distinguish between hardware faults and software faults. Otherwise, it will take a lot of effort to move the computer to the computer market. The shopkeeper will tell you what it will do when the software fails. In particular, startup faults may also be caused by software faults. Next, let's take a look at the startup exceptions caused by software faults.

I. CMOS setup Error

If the hard disk settings in CMOS setup are incorrect, the hard disk cannot be started with the operating system (Windows) in the hard disk because the computer cannot identify the hard disk. Check the content of CMOS setup when the image appears but cannot be started. To correctly identify the hard disk, you can use the "Ide HDD Auto Detection" option in CMOS setup.

Ii. System File errors

When Windows is started, four files, command.com, Io. sys, msdos. sys, and drvspace. Bin, are required. If these files are damaged, they cannot be started even if the hard disk is identified. You can use the "sys.com" file to restore these files. After starting with the boot disk, type "sys C.

Iii. File initialization error

Windows reads "autoexec. bat "," config. sys "," system. ini "," win. INI "," user. dat "," system. dat. However, if an error occurs during reading, the startup will fail. These files are difficult to recover, so you need to use methods such as Windows resetting. However, this is not a hardware fault. You do not need to take your computer to the computer market.
Iv. Windows errors most of the faults on the Windows initial screen are software faults. Conflicts between programs or driver issues. This problem can be solved by reading books and other methods.

Iii. hardware faults that are not faulty

Although it is not a fault, user assembly is often incorrect or the plug-in is loose. In this case, you can turn on your computer to check for wiring, plug-in, and other errors. When purchasing new hard drive, CD-ROM and other Eide devices, be sure to set the device in the middle to "slavee", set the device connected to the edge to "master ", an error may occur when the device cannot be started or used if the device is set incorrectly.

Iv. hardware fault detection methods

Next, let's take a look at the basic test methods for hardware faults. When the monitor does not have any image, you can use the following method to test the faulty part.

1. Prepare a workbench first.

2. Remove the motherboard from the chassis, unplug all the components on the motherboard, leaving only the CPU and ram, and then place the motherboard on the workbench.

3. Connect the regulated power supply to the motherboard.

4. Insert the video card into the AGP slot. Of course, if it is a PCI graphics card, it is inserted into the PCI slot. When inserting a video card, make sure that the gold-plated part of the video card is completely inserted into the slot.

5. Connect the video card to the monitor after connecting the power plug-in of the monitor.

6. Turn on the power of the monitor, and then turn on the power switch of the chassis. Then use a metal rod to access the power switch of the motherboard.

The power switch of the motherboard is the part connected to the power switch of the chassis, which is generally marked as "pwr sw" or "Power se ".

7. If the BIOS version information is displayed on the screen and the screen is normal, the CPU, motherboard, Ram, video card, and power supply are normal. generally, the component that is prone to failures is in the order of "graphics card", "motherboard", and "Hard Disk.

8. Connect the hard disk and the soft area for detection. Connect the CD-ROM detection, then the sound card. Modem and other connections. If no picture is displayed, it indicates that the connected component is faulty or has compatibility problems. Only the faulty part must be processed.

9. Chassis Problems

Sometimes an error occurs when installing the motherboard to the chassis, causing startup failure. Therefore, if there is no problem in the above part check, you can install the motherboard on the chassis for testing. If there are no errors in the test, it indicates a CMOS setup error, a driver, and other software problems.

A simple method for detecting computer faults

If "false fault" is ruled out, the fault actually exists! If you check the appearance of each accessory, including opening the chassis and seeing no signs of high-voltage damage or obvious scars on the surface of each component inside the host, if any, the faulty parts are clear. If none of them exist, try the following solution first.

1. Clear dust

Dust floating in the air is a major killer of computers. After using it for a while, it may cause a fault due to the dust accumulation of key components such as the motherboard, even in a dedicated equipment room. Therefore, the computer that has been used for a long time should be cleaned first, and the dust on the motherboard and peripherals should be gently flushed with a brush. If the dust is cleared or there is no dust, the fault still exists, it indicates that the hardware has other problems.

In addition, some plug-in cards or chips on the board use the plug-in form, vibration, dust, and other reasons often cause pin oxidation, poor contact. You can use an eraser to erase the surface oxide layer. After re-inserting the layer, start the system and check whether the fault is rectified.

If you use a keyboard for a long time, the keyboard may suffer from failures such as electric leakage and key freezing. The fault should be handled in a timely manner. Otherwise, the input file may contain incorrect characters. During processing, the keyboard should be held up with a bracket, press down, open the back cover of the keyboard, use alcohol to clean the contact of the circuit board and buttons, and properly pick up the shrapnel under the stuck button, to restore the original elasticity.

Note: When a floppy disk is used, when a dirty or scratched floppy disk is inserted into a floppy disk, the reading and writing head will be scratched and the floppy disk will be damaged. When cleaning the head, you must be very careful. If you do not need a soft drive for a long time, there may be rust on the head. At this time, you cannot use a cleaning disk. The specific method is to open the chassis and drop the cleaning agent on the head, after being soaked for half an hour, wipe it with grease cotton carefully. If you blindly use the cleaning disk, it will inevitably lead to damage to the Read and Write headers of the drive, and the drive will be decommissioned.

2. watching, listening, smelling, and touching

"Look": Check whether the system board plug, socket is skewed, resistance, capacitor pin touch, whether there are burning marks on the surface, whether the chip surface is cracked, whether the copper foil on the motherboard is burned out. Of course, you do not need to know whether there is a foreign body falling between the main board components (this will cause a short circuit), you can also see whether there is a burning color on the board, whether the wire (copper foil) on the printed circuit board is broken or not.

"Listen" is to listen to power fans, soft/hard drive motors, track agencies, display transformers, and other equipment operating sound is normal. In addition, system short-circuit failures often occur with abnormal sound. Monitoring can detect some potential accidents in time and take immediate measures before the accidents.

"Smell" is to identify whether there is a burning smell in the host and board, to facilitate the discovery of faults and determine the location of the short circuit.

Click "Touch" to press the active chip of the tube seat by hand to see if the chip is loose or has poor contact. In addition, when the system is running, you can use a hand touch or a shell close to the CPU, display, hard disk, and other devices to determine whether the device is running normally based on the temperature. You can use a hand to touch the surface of some chips, if it is hot, the chip is damaged.

3. Plugging Detection

As mentioned above, there are many causes of computer faults, including motherboard faults, I/O bus faults, and various plug-in card faults. Plugging and maintenance is a simple method to determine whether a fault occurs on the main board or I/O equipment. After the plug-in board is shut down, the plug-in board is pulled out one by one. After each piece of board is pulled out, the system starts up to observe the running status of the machine. Once a piece is pulled out, the main board runs normally, the fault is caused by the plug-in board failure or the corresponding I/O bus slot and load circuit failure. If the system still fails to start normally after all plug-in boards are removed, the fault may occur on the motherboard.

During plugging detection, computer faults can also be ruled out from another aspect: some chips, boards, and slots have poor contact, plugging out these chips and boards and re-inserting them correctly can solve the fault of microcomputer components caused by improper installation and contact.

4. Exchange Detection

The plug-in boards with the same model, bus mode, and function are exchanged with each other. The fault can also be determined based on the change of the fault phenomenon. This method is used in easily plugging maintenance environments, such as memory self-check errors. The same memory chip or memory module can be exchanged to determine the fault location. The fault can be exchanged between non-Faulty Chips, if the fault changes after the switch, it indicates that one part of the switch chip is bad, and the part can be further determined through the block-by-block switch. If the computer components or peripherals of the same model can be found, the exchange method can be used to quickly determine whether the components are quality problems.

5. Comparison Detection

Run two or more computers of the same type or different type. The fault location can be preliminarily determined based on the different performance of the normal computer and the faulty microcomputer when performing the same operation.

6. Vibration percussion Detection

Gently tap your finger on the chassis. If the fault is rectified, the fault is caused by poor contact or virtual welding. Then, you can further check the location of the fault point and eliminate it, but such a fault is difficult to detect the exact location.

7. Temperature Rise and cooling Detection

By artificially increasing the temperature of the computer operating environment, various components, especially the high temperature of the CPU, can be tested, so as to detect potential accidents as soon as possible. If the fault occurrence rate is greatly reduced after the temperature of the operating environment is reduced, it indicates that the fault is in a high temperature or cannot be high temperature resistant component, which can help narrow the fault diagnosis scope.

As a matter of fact, the temperature rise and reduction method uses the fault promotion principle to facilitate frequent occurrence of Faults Based on the conditions for manufacturing faults, so as to observe and judge the location of faults, only pay attention to control the heating method during implementation, and the temperature cannot exceed 40 degrees Celsius.

8. Run the detection program

With the wide application of various integrated circuits, the welding process becomes more and more complex, and it is difficult to find the fault only by the general maintenance means, however, through random diagnostic procedures, dedicated maintenance diagnostic cards, and various technical parameters (such as the interface address), Self-compiled special diagnostic programs to assist in detection, often get twice the result with half the effort. The principle of program testing is to use the software to send data and commands, and identify the fault location by reading the line status and a certain chip (such as a register) status. This method is often used to check various interface circuit faults and various circuits with address parameters. However, the premise of application is that the CPU and bus are basically running normally and can run relevant diagnostic software, able to run diagnostic cards installed on I/O bus slots.

When selecting the diagnosis program, it must be rigorous, comprehensive, and targeted, so that regular signals can be generated in some key parts, repeated tests can be performed on dual faults, and error records can be displayed.

How to diagnose computer faults

Many beginners have a sense of fear when they are new to computers and think that computer failures must be insurmountable. In fact, most computer failures have a certain rule to follow. This problem is like a piece of window paper, which can be broken at a glance and does not require you to have too much computer knowledge. Next let's learn a few quick methods to diagnose computer faults.

Environment Check Method

For some unexpected hardware faults, such as no display at startup. We should not consider it in depth, because we often ignore some details. First, let's look at the obvious things: Are there any power-on? Is the switch enabled? Is the power outlet powered? Are all connections connected? Perhaps the root cause of the problem lies in it.

CMOS reduction

Some users often change some settings in the motherboard CMOS due to curiosity, which is a major cause of failure. If the computer fails, we can solve the problem by restoring the CMOS settings. The method is very simple. Press the "delete" key on the keyboard to enter the CMOS of the motherboard, and select "load optimized defaults" (load the default setting ), press "Y" to save and exit CMOS.

Registry restoration method

Some users like to optimize or customize the system by modifying the registry, and some users are modified by malicious programs when browsing the Internet, some faults are caused by abnormal changes to the registry. Then we can restart the computer, and switch to the MS-DOS mode, enter and execute "scanreg/restore" under the C drive root directory to enter the registry recovery interface, then, select a registry file when the computer is finished and perform "Restore (Restore)" to restore the registry.

Simplified startup Method

All programs except logging, scanregistry, and systemtray. If a fault does not occur after the computer is restarted, most of the problems are caused by a self-starting software.

Logged Tracing Method

If the computer is no longer in Windows or is abnormal, we can use the logged (/bootlog.txtpipeline formula to start the computation machine. The generated bootlog.txt file can record the location where the fault occurred. Copy the hosts file to a floppy disk and open it on another computer. You will find that the entire Windows Startup Process is recorded and the root cause of the problem can be found.

Device replacement method

If you suspect that a device has a problem, replace it with a device of the same function (preferably the same model). If the problem disappears after replacement, most of the time there is a problem with this device.

Minimum System Method

If you are not sure which hardware is faulty, you can use the minimum system method to determine. The minimum system method is to remove other hardware devices from the system, and retain only the motherboard, memory, and video card. Then, start the system and check whether there are any faults. If any, other hardware problems can be ruled out. The fault should come from the existing three hardware. If not, add other hardware one by one to check which hardware is added and the fault is found. Then, process the hardware.

Program Upgrade Method

Many people do not pay enough attention to the driver and think that you can simply install one. However, we already have drivers when purchasing hardware. Why should hardware vendors keep releasing new versions of drivers? In fact, the purpose of doing so is to make the manufacturer's own products more perfect.

Because the current hardware update speed is fast, and most hardware manufacturers develop hardware before software development, the drivers supporting hardware may have some minor bugs when they are just released, these defects need to be remedied by constantly updating the driver. Therefore, upgrading the driver is also an effective solution to hardware faults.

Software Testing

Hardware fault diagnosis usually requires some hardware information, but many people do not have the habit of recording hardware information or do not know how to record it. If a computer fails, it may not be able to enter the system. At this time, we need a hardware testing tool under DOS, such as hwinfo for DOS, which is only 582kb in size, it can be carried with you on a floppy disk to diagnose hardware faults at any time.

Change Resource Method

Many computer faults are caused by resource conflicts between hardware. Therefore, we can change resources to solve these problems. Right-click my computer, select Properties from the drop-down menu, click Device Manager, and select View devices by type ", if a device is marked with a yellow exclamation mark in the list, it is likely that there is a resource conflict between hardware. To change a resource, double-click the hardware marked with an exclamation point with the left mouse button, select "resource", remove the check box before "use automatic settings", and select "change settings ", change the conflicting resource.