UNDERSTANDING COMPUTER SYSTEM TROUBLESHOOTING

INTRODUCTION TO HARDWARE TROUBLESHOOTING

Hardware troubleshooting is the process of reviewing, diagnosing and identifying operational or technical problems within an hardware device or equipment. It aims to resolve physical, logical problems and issues within a computing hardware. Hardware troubleshooting is done by hardware or technical support technician.

Hardware troubleshooting processes primarily aim to resolve computer hardware problems using a systematic approach. 

The process starts by first identifying the problem and finding different issues that can cause such a problem and eventually leading to implementing a solution or alternative. 

Hardware troubleshooting is generally done on hardware equipment installed within a computer, server, laptop or related device.

IDENTIFYING HARDWARE PROBLEMS, SOFTWARE PROBLEMS AND CONFIGURATION PROBLEMS

One of the first steps in troubleshooting a computer problem (or any other programmable system problem) is to determine whether the problem is due to a hardware failure or to faulty software. In most computers, you can use a significant event that occurs during the startup process as a key to separate hardware problems from software problems: the single beep that most computer produces between the end of the power-on self test (POST) and the beginning of the startup process.

Errors that occur, or are displayed, before this beep indicate that a hardware problem of some type exists. Up to this point in the operation of the system, only the BIOS and the basic system hardware have been active. The operating system side of the system does not come into play until after the beep occurs.

If the system produces an error message (such as “The system has detected unstable RAM at location x”) or a beep code before the single beep occurs, the system has found a problem with the hardware. In this case, a bad RAM memory device is indicated.

Typically, if the startup process reaches the point at which the system’s CMOS configuration information is displayed onscreen, you can safely assume that no hardware configuration conflicts exist in the system’s basic components. After this point in the bootup process, the system begins loading drivers for optional devices and additional memory.

If the error occurs after the CMOS screen displays and before the bootup tone, you must clean boot the system and single-step through the remainder of the bootup sequence.

You can still group errors that occur before the beep into two distinct categories:

➤ Configuration errors

➤ Hardware failures

A special category of problems tends to occur when a new hardware option is added to the system, or when the system is used for the very first time. These problems are called configuration problems, or setup problems. These problems result from mismatches between the system’s programmed configuration held in CMOS memory and the actual equipment installed in the system.

It is usually necessary to access the system’s CMOS setup utility in the following three situations:

➤ When the system is first constructed.

➤ When it becomes necessary to replace the CMOS backup battery on the system board.

➤ When a new or different option is added to the system (such as memory devices, hard drives, floppy drives, or video display), it might be necessary to access the setup utility to accept the changes that have been implemented.

In most systems, the BIOS and operating system use plug-and-play techniques to detect new hardware that has been installed in the system. These components work together with the device to allocate system resources for the device. In some situations, the PnP logic is not able to resolve all the system’s resource needs and a configuration error occurs. In these cases, the user must manually resolve the configuration problem.

When you are installing new hardware or software options, be aware of the possibility of configuration errors occurring. If you encounter configuration (or setup) errors, refer to the installation instructions found in the new component’s installation/user documentation.

If you cannot confirm a configuration problem, you most likely have a defective component. The most widely used repair method involves substituting known to good components for suspected bad components. Other alternatives for isolating and correcting a hardware failure that appears before the bootup depend on how much of the system is operable.

Normally, symptoms can be divided into three sections: configuration problems, bootup problems, and operational problems.

The system’s configuration settings are normally checked first. It is important to observe the system’s symptoms to determine in which part of the system’s operation the fault occurs. The error messages described in Table below are errors that occur and are reported before the single beep tone is produced at the end of the POST routines.

After the beep tone has been produced in the startup sequence, the system shifts over to the process of booting up and begins looking for and loading the operating system. Errors that occur between the beep and the presentation of the operating system’s user interface (command prompt or GUI) generally have three possible sources. These sources are summarized in the following list that includes the typical error messages associated with each source.

➤ Hardware failure (physical problem with the boot drive)

➤ General Failure Error Reading Drive C:

➤ Corrupted or missing boot files

➤ Bad or Missing Command Interpreter

➤ Non-system Disk or Disk Error

➤ Bad File Allocation Table

➤ Corrupted or missing operating system files

Both configuration problems and bootup problems can be caused by a hardware or operational failure. If the configuration settings are correct, but these symptoms are present, a hardware problem is indicated as the cause of the problem. Conversely, bootup problems are typically associated with the operating system.

HARDWARE TROUBLESHOOTING TOOLS

The general troubleshooting techniques most often performed on a computer hardware is exchanging Failed Replaceable Devices. Due to the relative low cost of computer components, it is normally not practical to troubleshoot failed components to the IC level, like RAM, Hard-disk etc. The cost of diagnosing and repairing small computer devices may be lead to a greater expense.

However, a few hardware diagnostic tools can be very helpful in isolating defective hardware components. These tools include

➤ Software diagnostic disk

➤ Multimeter

➤ Cable tester

➤ POST card

SOFTWARE DIAGNOSTIC PACKAGE

Several commercially available disk-based diagnostic routines can check the system by running predetermined tests on different areas of its hardware. The diagnostic package evaluates the response from each test and attempts to produce a status report for all of the system’s major components. Like the computer’s self-tests, these packages produce visual and beep-coded error messages.

The most common software-troubleshooting packages test the system’s memory, microprocessor, keyboard, display monitor, and the disk drive’s speed. If at least the system’s CPU, disk drive, and clock circuits are working, you might be able to use one of these special software-troubleshooting packages to help localize system failures. They can prove especially helpful when trying to track down non-heat-related intermittent problems.

If a diagnostic program indicates that multiple items should be replaced, replace the units one at a time until the unit starts up. Then replace any units removed prior to the one that caused the system to start. This process ensures that there are not multiple bad parts. If you have replaced all the parts, and the unit still does not function properly, the diagnostic software is suspect.

The final solution and measure that can be established on a computer software, be it application software or System software, is reinstalling the Software to replace the missing or corrupt files. In terms of a malfunctioning Operating System (OS) you reinstall the operating system.

WORKING WITH MULTI-METER

A number of test instruments can help you isolate computer hardware problems. One of the most basic pieces of electronic troubleshooting equipment is the multimeter. These test instruments are available in both analog and digital readout form and can be used to directly measure electrical values of voltage (V), current in milliamperes (mA) or amperes (A), and resistance in ohms. Therefore, these devices are referred to as VOMs (volt-ohmmilliammeters) for analog types, or DMMs (digital multimeters) for digital types.

Figure 3.2 depicts a digital multimeter. With a little finesse, you can use this device to check diodes, transistors, capacitors, motor windings, relays, and coils. This particular DMM contains facilities built in to the meter to test transistors and diodes. These facilities are in addition to its standard functions of current, voltage, and resistance measurement; however, in computer repair work, only the voltage and resistance functions are used extensively.

          A digital Multimeter

The first step in using the multimeter to perform tests is to select the proper function. For the most part, you never need to use the current function of the multimeter when working with computer systems; however, the voltage and resistance functions can be very valuable tools.

In computer troubleshooting, most of the tests are DC voltage readings. These measurements usually involve checking the DC side of the powersupply unit. You can make these readings between ground and one of the expansion-slot pins, or at the system board power-supply connector. It is also common to check the voltage level across a system board capacitor to verify that the system is receiving power. The voltage across most of the capacitors on the system board is 5V (DC). The DC voltages that can normally be expected in a PC-compatible system are +12V, +5V, –5V, and –12V. The actual values for these readings might vary by 5% in either direction.

Note: it is a normal practice to all set the multimeter to its highest voltage range to be certain that the voltage level being measured does not damage the multimeter.

The DC voltage function is used to take measurements in live DC circuits. It should be connected in parallel with the device being checked. This could mean connecting the reference lead (black lead) to a ground point and the measuring lead (red lead) to a test point to take a measurement as illustrated in the figure below. The figure show the DC voltage check on a PC motherboard