Introduction
When a computer system fails, there are generally two possible causes—hardware or software. This section of computer repair is dedicated to symptoms and techniques associated with diagnosing and repairing failures associated with different hardware components. The section of computer repair is broken into individual sections dedicated to each type of hardware component. It begins with failures and symptoms associated with the power-supply unit and moves through system boards, input devices, video displays, disk drive systems, I/O ports, modems, and sound cards. Numerous symptoms and problem sources are presented for each of these components. Technicians need to be aware of the different symptoms produced by these devices so that they can move through the diagnostic and repair processes in the most efficient manner possible. After completing the section of computer repair , you should be able to identify common symptoms and problems associated with each hardware module and know how to isolate, troubleshoot, and repair the problems.
ISOLATING POWER-SUPPLY PROBLEMS
Typical symptoms associated with power-supply failures include
· No indicator lights visible, with no disk drive action, and no display on the screen. Nothing works, and the system is dead.
· The On/Off indicator lights are visible, but there is no disk drive action and no display on the monitor screen. The system fan might or might not run.
· The system produces a continuous beep tone.
Checking Dead Systems
Special consideration must be taken when a system is inoperable. In a totally inoperable system, there are no symptoms to give clues where to begin the isolation process. In addition, it is impossible to use troubleshooting software or other system aids to help isolate the problem. When the system exhibits no signs of life—including the absence of lights—the best place to start looking for the problem is at the power supply. The operation of this unit affects virtually every part of the system. Also, the absence of any lights working usually indicates that no power is being supplied to the system by the power supply.
1. Begin by checking the external connections of the power supply. This is the first step in checking any electrical equipment that shows no signs of life.
2. Confirm that the power supply cord is plugged in to a functioning outlet.
3. Check the position of the On/Off switch.
4. Examine the power cord for good connection at the rear of the unit.
5. Check the setting of the 110/220 switch setting on the outside of the power supply. The normal setting for equipment used in the United States is 110 and here in Nigeria is 220
6. Check the power at the commercial receptacle using a voltmeter, or by plugging in a lamp (or other 220-volt device) into the outlet.
Other Power-Supply Problems
The presence of the lights and the fan operation indicate that power is reaching the system and that at least some portion of the power supply is functional. This type of symptom results from the following two likely possibilities:
· A portion of the power supply has failed or is being overloaded. One or more of the basic voltages supplied by the power supply is missing while the others are still present.
· A key component on the system board has failed, preventing it from processing even though the system has power. A defective capacitor across the power input of the system board can completely prevent it from operating.
TROUBLESHOOTING THE SYSTEM BOARD
As with any troubleshooting procedure, begin by observing the symptoms produced by bootup and operation. Observe the steps that lead to the failure and determine under what conditions the system failed. Were any unusual operations in progress? Note any error messages or beep codes. Refer to the User Manuals for the system board and peripheral units to check for configuration problems. Examine the CMOS setup entries for configuration problems. In Pentium systems, also check the advanced CMOS setup parameters to make certain that all the appropriate system board–enabling settings have been made. The microprocessor, RAM modules, ROM BIOS, CMOS battery, and possibly cache ICs are typically replaceable units on the system board. If enough of the system is running to perform tests on these units, you can replace them. Problems with key system board components produce symptoms similar to those described for a bad power supply. Both the microprocessor and the ROM BIOS can be sources of such problems. You should check both by substitution
when dead system symptoms are encountered, but the power supply is good. In addition to containing the circuitry that directs all the system’s operations, the system board contains a number of other circuits on
which the rest of the system’s components depend. These include the system’s DRAM memory (which all software programs use) and the system’s data, address, and signal buses (that is, expansion slots).
System Board Symptoms
Typical symptoms associated with system board hardware failures include
· The On/Off indicator lights are visible and the display is visible on the monitor screen, but there is no disk drive action and no bootup occurs.
· The On/Off indicator lights are visible and the hard drive spins up, but the system appears dead and there is no bootup.
· The system locks up during normal operation.
· The system produces a beep code with one, two, three, five, seven, or nine beeps.
· The system produces a beep code of one long and three short beeps.
· The system will not hold the correct date and time.
· An “8042 Gate A20 Error” message displays—Error getting into Protected mode.
· An “Invalid Switch Memory Failure” message displays.
· A “DMA Error” message displays—DMA Controller failed page register test.
· A “CMOS Battery Low” message displays, indicating failure of CMOS battery or CMOS checksum test.
· A “CMOS System Option Not Set” message displays, indicating failure of CMOS battery or CMOS checksum test.
· A “CMOS Checksum Failure” message displays, indicating CMOS battery low or CMOS checksum test failure.
· A 201 error code displays, indicating a RAM failure.
· A parity check error message displays, indicating a RAM error.
Typical symptoms associated with system board CMOS Setup failures include:
· A “CMOS Inoperational” message displays—Failure of CMOS shutdown register.
· A “Display Switch Setting Not Proper” message displays— Failure to verify display type.
· A “CMOS Display Mismatch” message displays—Failure of display type verification.
· A “CMOS Memory Size Mismatch” message displays—System
· Configuration and Setup failure.
· A “CMOS Time and Date Not Set” message displays—System
· Configuration and Setup failure.
· An IBM-compatible error code displays, indicating that a configuration problem has occurred.
Typical symptoms associated with system board I/O failures include the following:
· Speaker doesn’t work during operation. The rest of the system works, but no sounds are produced through the speaker.
· Keyboard does not function after being replaced with a known good unit.
Configuration Checks
Normally, the only time a configuration problem occurs is when the system is being set up for the first time or when a new option has been installed. The values stored in CMOS must accurately reflect the configuration of the system; otherwise, an error occurs. Incorrectly set CMOS parameters will cause the corresponding hardware to fail. Therefore, check the enabling functions of the advanced CMOS settings as a part of every hardware configuration troubleshooting procedure. Check the advanced CMOS configuration and enabling settings in the BIOS and Chipset Features screens. These settings, usually include the disk drives, keyboard, and video options, as well as onboard serial and parallel ports. In addition, the user can turn on or off certain sections of the system’s RAM for shadowing purposes and establish parity or non-parity memory operations. You can access these configuration settings for change by pressing a predetermined key combination during the boot-up procedure. The complexity of modern system boards has created a huge number of configuration options for the CMOS, as reflected in the complexity of their advanced CMOS configuration screens. When working with these settings, it is very easy to place the system in a condition where it cannot respond. Because the problem is at the BIOS level, it might be difficult to get back into the CMOS to correct the problem. Therefore, system designers have included a couple of options to safeguard the system from this condition. In some BIOS, holding down the Delete key throughout the startup erases the CMOS contents and starts from scratch. Jumpers that can be set to start the contents from a bare-essentials setting can also be placed on the system board. In either case, you must rebuild any advanced features in the CMOS configuration afterward. Newer system boards have an auto-configuration mode that takes over most of the setup decisions. This option works well in the majority of applications. Its settings produce an efficient, basic level of operation for standard devices in the system. However, they do not optimize the performance of the system. To accomplish that, you must turn off the auto-configuration feature and manually insert the desired parameters into the configuration table.
Using power-on defaults for auto-configuration loads the most conservative options possible into the system from the BIOS. This is the most effective way to detect BIOS-related system problems. These settings replace any user-entered configuration information in the CMOS setup registers. All memory caching is turned off, and all wait states are set to maximum. This enables the most basic part of the system to start up. If these default values fail to get the system to boot up, it is an indication of hardware problems (such as incorrect jumper settings or bad hardware components). Using auto-configuration with BIOS defaults provides a little more flexibility than the power-on option. If you have entered an improper configuration setting and cannot determine which setting is causing the problem, this option is suggested. Like the power-on option, this selection replaces the user-supplied configuration settings with a new set of parameters from the BIOS. Choosing this option will likely get you back into the CMOS setup screen so that you can track down the problem. It is also the recommended starting point for optimizing the system’s operation.
Hardware Checks
If the system’s CMOS configuration setup appears to be correct and a system board hardware problem is suspected, you probably need to exchange the system board for a working unit. Because most of the system must be dismantled to exchange it, a few items are worth checking before doing so. Check the system board for signs of physical problems, such as loose cables and devices. If nothing is apparently wrong, check the power supply voltage levels on the system board. Check for +5V and +12V (DC) on the system board., If these voltages are missing, turn off the system, disconnect power to all disk drives, and swap the power-supply unit with a known good one Finally, consider checking the FRU devices present on the board. Normally, a few serviceable items on the system board might be checked by substitution before doing so. These include the RAM modules, the microprocessor (and its cooling fan), the ROM BIOS, and the system battery.
RAM
The system board’s memory is a very serviceable part of the system. RAM failures basically fall into two major categories and create two different types of failures:
· Soft-memory errors—Errors caused by infrequent and random glitches in the operation of applications and the system. You can clear these events just by restarting the system.
· Hard-memory errors—Permanent physical failures that generate NMI errors in the system and require that the memory units be checked by substitution. Observe the boot-up RAM count on the display to verify that it is correct for the amount of physical RAM actually installed in the system. If not, swap RAM devices around to see whether the count. changes. Use logical rotation of the RAM devices to locate the defective part. The burn-in tests in most diagnostic packages can prove helpful in locating borderline RAM modules. You can also swap out RAM modules in a one-at-a-time manner to isolate defective modules. When swapping RAM into a system for troubleshooting purposes, take care to ensure that the new RAM is of the correct type for the system and that it meets its bus speed rating. Also, make sure that the replacement RAM is consistent with the installed RAM. Mixing RAM types and speeds can cause the system to lock up and produce hard memory errors.
Microprocessor
In the case of a microprocessor failure, the system might issue a slow, single beep from the speaker along with no display or other I/O operation. This indicates that an internal error has disabled a portion of the processor’s internal circuitry (usually the internal cache). Internal problems also might allow the microprocessor to begin processing, but then fail as it attempts operations. Such a problem results in the system continuously counting RAM during the boot-up process. It also might lock up while counting RAM. In either case, the only way to remedy the problem is to replace the microprocessor. If the system consistently locks up after being on for a few minutes, this is a good indication that the microprocessor’s fan is not running or that some other heat buildup problem is occurring. You also should check the microprocessor if its fan has not been running, but the power is on. This situation might indicate that the microprocessor has been without adequate ventilation and has overheated. When this happens, you must replace the fan unit and the microprocessor. Check to make certain that the new fan works correctly; otherwise, a second microprocessor will be damaged.
ROM
As with the microprocessor, a bad or damaged ROM BIOS typically stops the system dead. When you encounter a dead system board, examine the BIOS chip(s) for physical damage. Another symptom associated with damaged BIOS causes the startup sequence to move into the CMOS configuration display but then never returns to the boot-up sequence. In any case, you must replace the defective BIOS with a version that matches the chipset used by the system.
Battery
The second condition that causes a configuration problem involves the system board’s CMOS backup battery. If a system refuses to maintain time and date information, the CMOS backup battery, or its recharging circuitry, is normally faulty. After the backup battery has been replaced, check the contacts of the battery holder for corrosion. If the battery fails or if it has been changed, the contents of the CMOS Configuration will be lost. After replacing the battery, it is always necessary to run the CMOS Setup utility to reconfigure the system.
TROUBLESHOOTING VIDEO
Basically, there are two levels of troubleshooting that apply to video problems: configuration and hardware problems. In the case of hardware problems, the components associated with video problems include the video adapter card, the monitor, and to a lesser degree, the system board. Figure below depicts the components
associated with the video display. Information intended for the video display monitor moves from the system board to the video adapter card by way of the system board’s expansion slots. The adapter card also obtains power for its operation from these expansion slots. Finally, the information is applied to the monitor through the video signal cable.
Common symptoms associated with display problems include the following:
· No display.
· Wrong characters displayed onscreen.
· Diagonal lines onscreen (no horizontal control).
· Display scrolls (no vertical control).
· An error code of one long and six short beeps is produced by the system.
· A “Display Switch Setting Not Proper—Failure to verify display type” error displays.
· A “CMOS Display Mismatch—Failure to verify display type” error displays.
· An error code of one long and two short beeps indicates a display adapter problem.
· Characters are fuzzy.
· Monitor only displays a single color.
Windows Video Checks
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| Testing VGA |
You can gain access to the Windows video information by doubleclicking the Control Panel’s Display icon. From the Display page, there are a series of tabs at the top of the screen. Of particular interest is the Settings tab. Under this tab, the Change Display Type button provides access to both the adapter type and monitor type settings. In the Adapter type window, information about the adapter’s manufacturer, version number, and current driver files is given. Clicking the Change button beside this window brings a listing of available drivers to select from. You also can use the Have Disk button with an OEM disk to install video drivers not included in the list. You also can alter the manner in which the list displays by choosing the Show Compatible Devices or the Show All Devices options. In the Monitor type window, there is an option list for both manufacturers and models. You also can use this function with the Have Disk button to establish OEM settings for the monitor. You can access additional Windows video information under the Control Panel’s System icon. Inside the System Properties page, click the Device Manager and select the Display Adapters option from the list. Double-click the monitor icon that appears as a branch. The adapter’s Properties page pops up onscreen. From this page, the Driver tab reveals the driver file in use. Selecting the Resources tab displays the video adapter’s register address ranges and the video memory address range. You can manipulate these settings manually by clicking the Change Setting button.
The first step when isolating Windows video problems involves checking the video drivers. Check for the drivers in the locations specified in the previous paragraphs. If the video driver from the listis not correct, reload the correct driver. If a Windows video problem prevents you from viewing the driver list, restart the system, press the F8 function key when the Starting Windows message appears, and select Safe Mode. This should load Windows with the standard 640x480x16-color VGA driver (the most fundamental driver available for VGA monitors), and should furnish a starting point for installing the correct driver for the monitor being used. If the problem reappears when a higher resolution driver is selected, refer to the Color Palette box under the Control Panel’s Display option/Settings tab and try minimum color settings. If the problem goes away, contact the Microsoft Download Service (MSDL) or the adapter card maker for a new, compatible video driver. If the problem remains, reinstall the driver from the Windows 9x distribution disk or CD. If the video is distorted or rolling, try an alternative video driver from the list.
Video Hardware Checks
If you suspect a video display hardware problem, the first task is to check the monitor’s On/Off switch to see that it is in the On position.Also, check the monitor’s power cord to see that it is either plugged in to the power supply’s monitor outlet, or into an active 120V (AC) commercial outlet. Also check the monitor’s intensity and contrast controls to make certain that they are not turned down. The next step is to determine which of the video-related components is involved. On most monitors, you can do this by simply removing the video signal cable from the adapter card. If a raster appears onscreen with the signal cable removed, the problem is probably system related, and the monitor is good. If the monitor is an EPA-certified Energy Star–compliant monitor, this test might not work. Monitors that possess this power-saving feature revert to a low-power mode when they do not receive a signal change for a given period of time. With the system off, remove any multimedia-related cards such as VGA-to-TV converter cards and video capture cards. Try to reboot the system. If the system boots up and the display is correct with these options removed, you can safely assume that one of them is the cause of the problem. To verify which device is causing the problem, reinstall them, one at a time, until the problem reappears. The last device reinstalled before the problem reappeared is defective. Replace this item and continue reinstalling options, one at a time, until all the options have been reinstalled. Check the components associated with the video display monitor. Start by disconnecting the monitor’s signal cable from the video controller card at the rear of the system unit, and its power cord from the power-supply connector, or the 120V (AC) outlet. Then, exchange the monitor for a known good one of the same type (that Know what an Energy Star compliant monitor does that others do not. is, VGA for VGA). If the system boots up and the video display is correct, return the system to full service and service the defective monitor as indicated. If the display is still not correct, exchange the video controller card with a known good one of the same type. Remove the system unit’s outer cover. Disconnect the monitor’s signal cable from the video controller card. Swap the video controller card with a known good one of the same type. Other symptoms that point to the video adapter card include a shaky video display and a high-pitched squeal from the monitor or system unit.
TROUBLESHOOTING KEYBOARD PROBLEMS
Most of the circuitry associated with the computer’s keyboard is contained in the keyboard itself. However, some keyboard interface circuitry is located on the system board. Therefore, the steps required to isolate keyboard problems are usually confined to the keyboard, its connecting cable, and the system board. This arrangement makes isolating keyboard problems relatively easy. Just check the keyboard and the system board.
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| Keyboard with the systemboard |
Keyboard Symptoms
Typical symptoms associated with keyboard failures include the following:
· No characters appear onscreen when entered from the keyboard.
· Some keys work, whereas others do not work.
· A “Keyboard Is Locked—Unlock It” error displays.
· A “Keyboard Error—Keyboard Test Failure” error displays.
· A “KB/Interface Error—Keyboard Test Failure” error displays.
· An error code of six short beeps is produced during bootup.
· Wrong characters are displayed.
· An IBM-compatible 301 error code displays.
· Unplugged keyboard error.
· Stuck key.
Basic Keyboard Checks
The keys of the keyboard can wear out over time. This can result in keys that don’t make good contact (no character is produced when the key is pushed) or one that remains in contact (sticks) even when pressure is removed. The stuck key will produce an error message when the system detects it. However, it has no way of detecting an open key. If you detect a stuck key, or keys, you can desolder from the keyboard and replace the individual key switches with a good key from a manufacturer or a similar keyboard. amount of time spent repairing a keyboard quickly drives the cost of the repair beyond the cost of a new unit. An unplugged keyboard, or one with a bad signal cable will also produce a keyboard error message during startup. Ironically, this condition might produce a configuration error message that says “Press F1 to continue.” If the keyboard produces odd characters on the display, check the Windows keyboard settings in the Control Panel’s Device Manager. If the keyboard is not installed or is incorrect, install the correct keyboard type. Also, make certain that you have the correct language setting specified under the Control Panel’s keyboard icon.
Keyboard Hardware Checks
If you suspect a keyboard hardware problem, you must first isolate the keyboard as the definite source of the problem (a fairly easy ask). Because the keyboard is external to the system unit, is detachable, and is inexpensive, simply exchange it with a known good keyboard. If the new keyboard works correctly, return the system to full service and service the defective keyboard appropriately. Remove the back cover from the keyboard, check for the presence of a fuse in the +5V dc supply, and check it for continuity. Neither the standard 5-pin DIN nor the 6-pin PS/2 mini-DIN keyboards can be hot swapped. Disconnecting or plugging in a keyboard with this type of fuse while power is on can cause it to fail. If the fuse is present, simply replace it with a fuse of the same type and rating. If replacing the keyboard does not correct the problem and no configuration or software reason is apparent, the next step is to troubleshoot the keyboard receiver section of the system board. On most modern system boards, this ultimately involves replacing the system board with another one.
TROUBLESHOOTING MOUSE PROBLEMS
Most of the problems associated with mice involve the trackball. As the mouse is moved across the table, the trackball picks up dirt or lint, which can hinder the movement of the trackball, typically evident by the cursor periodically freezing and jumping onscreen. On most mice, you can remove the trackball from the mouse by a latching mechanism on its bottom. Twisting the latch counterclockwise enables you to remove the trackball. Then you can clean dirt out of the mouse.
Mouse Configuration Checks
When the mouse does not work in a Windows system, restart it and move into Safe Mode by pressing the F5 function key when the Starting Windows message is displayed. This will start the operating system with the most basic mouse driver available. If the mouse will not operate in Safe Mode, restart the system and check the CMOS Setup screen during bootup for the presence of the serial port that the mouse is connected to. If the mouse works in Safe Mode, click the Mouse icon in the Control Panel to check its configuration and settings. Follow this by checking the port configuration in Windows Control Panel. Consult the Device Manager entry under the Control Panel’s System icon. Select the Ports option, click the COM x properties option in the menu, and click Resources. Make certain that the selected IRQ and address range match that of the port. Click on the Mouse entry in the Device Manager and double-click its driver to obtain the Mouse Properties page. Move to the Resources tab as illustrated and check the IRQ and base address settings for the mouse in Windows. Compare these settings to the actual configuration settings of the hardware. If they differ, change the IRQ or base address setting in Windows to match those of the installed hardware If the correct driver is not available in the Windows list, place the manufacturer’s driver disk in the floppy drive and load it using the Other Mouse (requires disk from OEM) option. If the OEM driver fails to operate the mouse in Windows, contact the mouse manufacturer for an updated Windows driver. Windows normally supports mice only on COM1 and COM2. If several serial devices are being used in the system, you might have to establish alternative IRQ settings for COM3 and COM4. In older systems, check the directory structure of the system for a Mouse directory. Also, check for AUTOEXEC.BAT and CONFIG.SYS files that might contain conflicting device drivers. Two common driver files might be present: the MOUSE.COM file called for in the AUTOEXEC.BAT file and the MOUSE.SYS file referenced in the CONFIG.SYS file. If these files are present and have mouse lines that do not begin with a REM statement, they could be overriding the settings in the operating system. In particular, look for a DEVICE= command associated with the mouse.
Mouse Hardware Checks
For most systems, troubleshooting the mouse hardware involves isolating the mouse from its port circuitry. Just replace the mouse to test its electronics.If the replacement mouse works, the original mouse is probably defective. If the electronics are not working properly, few options are available for servicing the mouse. It might need a cleaning, or a new trackball. However, the low cost of a typical mouse generally makes it a throwaway item if simple cleaning does not fix it. If the new mouse does not work either, chances are very high that the mouse’s electronics are working properly. In this case, the driver software, or port hardware, must be the cause of the problem.
TROUBLESHOOTING MONITORS
The preceding sections cover the digital portion of the video system. Troubleshooting the actual monitor is discussed immediately following the video adapter troubleshooting sections. Only experienced technicians should participate in troubleshooting internal monitor problems because of the very high voltages present there. Figure below shows the components located inside a typical CRT color monitor. Of particular interest is the high-voltage anode that connects the tube to the high-voltage sections of the signal-processing board. This is a very dangerous connection that is not to be touched.
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| Monitor Troubleshooting |
Operation of a monitor with the cover removed poses a shock hazard from its power supply. Therefore, anyone unfamiliar with the safety precautions associated with high-voltage equipment should not attempt to service a video monitor. The high-voltage levels in the monitor do not necessarily disappear because the power to the monitor is turned off. Like television sets, monitors have circuitry capable of storing high-voltage potentials long after power has been removed. Always discharge the anode of the picture tube to the receiver chassis before handling the CRT tube. Because of the high voltage levels, you should never wear antistatic grounding straps when working inside the monitor. The builtup charge on the anode must the shorted to ground so that the monitor can be handled safely. This operation is typically performed with a large, long-handled crewdriver and a shorting clip. An additional hazard associated with handling CRTs is that the tube is fragile. Take extra care to prevent the neck of the tube from striking any surface. Never lift the tube by the neck—especially when removing or replacing a CRT tube in the chassis. If the picture tube’s envelope is cracked or ruptured, the inrush of air will cause a high-velocity implosion, and the glass will fly in all directions. Therefore, you should always wear protective goggles when handling picture tubes. Color monitors produces a relatively high level of X-radiation. The CRT tube is designed to limit X-radiation at its specified operating voltage. If a replacement CRT tube is being installed, make certain to replace it with one of the same type, and with suffix numbers that are the same. You can obtain this information from the chassis schematic diagram inside the monitor’s housing.
Diagnosing Monitor Problems
Check obvious items first. Examine the power cord to see that it is plugged in. Check to see that the monitor’s power switch is in the On position. Check the external settings to see that the brightness and contrast settings are not turned off. If the problem produces a blank display, disconnect the monitor’s signal cable from its video adapter card. If a raster appears, a video card problem is indicated. The final step in isolating the video monitor as the cause of the problem is to exchange it for a known good one. If the replacement works, the problem must be located in the monitor. Some display problems can actually be a cause by incorrectly set front panel display settings. The monitor’s front panel controls (either analog or digital) establish parameters for brightness, contrast, screen size and position, and focus. Typical problems associated with these controls include fuzzy characters, poor or missing colors, and incomplete displays. Actually, there can be several causes of fuzzy characters on the display. The first step in checking out this problem is to reset the display resolution to standard VGA values. If the fuzzy characters remain, check the intensity and contrast controls to see if they are out of adjustment. Finally, you might need to remove built-up electromagnetic fields from the screen through a process called degaussing. This can be done using a commercial degaussing coil. However, newer monitors have built-in degaussing circuits that can be engaged through their front panel controls. These monitors normally perform a degauss operation each time they are turned on. However, there are occurrences when the user might need to perform this operation. The front panel controls can also be used to adjust the Red/Green/Blue color mixture for the display. If the monitor is showing poor colors, or only one color, examine the color settings using the front panel controls. If these settings are responsive to change, the problem either exists in the video adapter or signal cable (broken or bad pin or conductor), or the monitor’s color circuitry is deteriorating.
TROUBLESHOOTING FLOPPY DISK DRIVES
Typical symptoms associated with floppy disk drive failures during bootup include the following:
· FDD errors are encountered during bootup.
· The front-panel indicator lights are visible, and the display is present on the monitor screen, but there is no disk drive action and no bootup.
· An IBM-compatible 6xx (such as 601) error code displays.
· An FDD Controller Error message displays, indicating a failure to verify the FDD setup by the System Configuration file.
The FDD activity light stays on constantly, indicating that the FDD signal cable is reversed.
Additional FDD error messages commonly encountered during normal system operation include:
· Disk Drive Read/Write/Seek Error messages.
· No Boot Record Found message, indicating that the system files in the disk’s boot sector are missing or have become corrupt.
· The system stops working while reading a disk, indicating that the contents of the disk have become contaminated. The drive displays the same directory listing for every disk inserted in the drive, indicating that the FDD’s disk-change detector or signal line is not functional. A number of things can cause improper floppy disk drive operation or disk drive failure. These items include the use of unformatted disks, incorrectly inserted disks, damaged disks, erased disks, loose cables, drive failure, adapter failure, system board failure, or a bad or loose power connector. Figure below depicts the components associated with the system’s floppy disk drives. All of these items can impact the operation of the floppy disk drive. Basically three levels of troubleshooting apply to FDD problems: configuration, media, and hardware levels. No Windows-level troubleshooting applies to floppy disk drives.
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| Troubleshooting Floppy Disk drive |
Basic FDD Checks
If there is a problem booting the system, examine the advanced CMOS Setup to check the boot-up order. The boot order can be set so that the FDD is never examined during the boot-up sequence. Try the floppy disk in a different computer to see whether it works in that machine. If not, there is most likely a problem with the format of the disk or the files on the disk. If the other computer can read the disk, you must troubleshoot the floppy disk drive hardware.
FDD Hardware Checks
Check the floppy disk drive’s signal cable for proper connection at both ends. In many systems, the pin-1 designation is difficult to see. Reversing the signal cable causes the FDD activity light to stay on continuously. The reversed signal cable will also erase the master boot record from the disk, making it non-bootable. Because this is a real possibility, you should always use an expendable backup copy of the boot disk for troubleshooting FDD problems. Exchange the suspect floppy disk drive with another one of the same type. Check the signal cable by substitution with a known good unit.
TROUBLESHOOTING HARD DISK DRIVES
Typical symptoms associated with hard disk drive failures include
· The computer does not boot up when turned on.
· The computer boots up to a system disk in the A: drive, but not to the hard drive, indicating that the system files on the HDD are missing or have become corrupt.
· No motor sounds are produced by the HDD while the computer is running. (In desktop units, the HDD should always run when power is applied to the system—this also applies to portables because of their advanced power-saving features.)
· An IBM-compatible 17xx error code is produced on the monitor screen.
· An HDD Controller Failure message displays, indicating a failure to verify hard disk setup by system configuration file error.
· A C: or D: Fixed Disk Drive Error message displays, indicating a hard disk CMOS setup failure.
· An “Invalid Media Type” message displays, indicating the controller cannot find a recognizable track/sector pattern on the drive.
· A “No Boot Record Found”, a “Non-System Disk or Disk Error”, or an “Invalid System Disk” message displays, indicating that the system boot files are not located in the root directory of the drive.
· The video display is active, but the HDD’s activity light remains on and no bootup occurs, indicating that the HDD’s CMOS configuration information is incorrect.
· An “Out of Disk Space” message displays, indicating that the amount of space on the disk is insufficient to carry out the desired operation.
· A “Missing Operating System” or a “Hard Drive Boot Failure” message displays, indicating that the disk’s master boot record is missing or has become corrupt.
· A “No ROM BASIC—System Halted” or “ROM BASIC Interpreter Not Found” message displays, followed by the system stopping, indicating that no master boot record was found in the system. This message is produced only by PCs, XTs, and some clones.
· A “Current Drive No Longer Valid” message displays, indicating that the HDD’s CMOS configuration information is incorrect or has become corrupt.
Hard drive systems are very much like floppy drive systems in structure— they have a controller, one or more signal cables, a power cable, and a drive unit. The troubleshooting procedure typically moves from setup and configuration, to formatting, and, finally, into the hardware component isolation process.
HDD Configuration Checks
While booting up the system, observe the BIOS’s HDD type information displayed on the monitor. Note the type of HDD that the BIOS recognizes as being installed in the system. The values stored in this CMOS memory must accurately reflect the actual HDD(s) format installed in the system; otherwise, an error occurs. Possible error messages associated with HDD configuration problems include the “Drive Mismatch Error” message and the “Invalid Media Type” message. Check the drive to make sure that it is properly terminated. Every drive type requires a termination block somewhere in the interface. On IDE drives, check the Master/Slave jumper setting to make sure that it is set properly for the drive’s logical position in the system.
Remember that there can only be one master drive selection on each IDE channel. If you have more than one device attached to a single interface cable, make sure that they are of the same type (that is, all are EIDE
devices or all are ATA100 devices). Mixing IDE device types will create a situation in which the system cannot provide the different types of control information each device needs. The drives are incompatible, and you might not be able to access either device. If the drive is a SCSI drive, check to see that its ID has been set correctly and that the SCSI chain has been terminated correctly. Either of these errors will result in the system not being able to see the drive. Check the CMOS Setup utility to make sure that SCSI support has been enabled, along with large SCSI drive support
Basic HDD Checks
The first task is to determine how extensive the HDD problem is. Place a clean boot disk or an Emergency Start disk in the A: drive and try to boot the system. Then, execute a DIR command to access the C: drive. If the system can see the contents of the drive, the boot files have been lost or corrupted but the architecture of the disk is intact.
Modify the DOS DIR command with an /AH or /AS switch (that is,DIR C: /AH or DIR C: /AS) to look in the root directory for the system files and the COMMAND.COM file. It is common to receive a Disk Boot Failure message onscreen if this type of situation occurs. The No (or Missing) ROM BASIC Interpreter message might also be produced by this condition. If the clean boot disk has a copy of the FDISK program on it, attempt to restore the drive’s master boot record (including its partition information) by typing the following: A>FDISK /MBR Providing that the hard disk can be accessed with the DIR command, type and enter the following command at the DOS prompt (with the clean boot disk still in the A: drive): SYS C: This command copies the IO.SYS, MSDOS.SYS, and COMMAND. COM system files from the boot disk to the hard disk drive. Turn off the system, remove the boot disk from the A: drive, and try to reboot the system from the hard drive. If the system cannot see the drive after booting to the floppy disk, an “Invalid Drive…” message or an “Invalid Drive Specification” message should be returned in response to any attempt to access the drive. Use the FDISK utility to partition the drive and then use the FORMAT command to make the disk bootable.
HDD Hardware Checks
If you cannot access the hard disk drive and its configuration settings are correct, you must troubleshoot the hardware components associated with the hard disk drive. These components include the drive, its signal cable, and the HDC (on the system board). Check the HDD signal cable for proper connection at both ends. Exchange the signal cable(s) for a known good one. Check the Master/Slave jumper settings to make sure that they are set correctly, Check to see whether the system might be using the Cable Select option also depicted in the figure. This setting requires a special CSEL signal cable designed to determine the master/slave arrangements for multiple IDE drives. Likewise, check the ID configuration settings and terminator installations for SCSI drives.
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| Hard Disk With jumper settings |
The next logical step might seem to be to replace the hard drive unit. However, it is quite possible that the hard drive might not have any real damage. It might have just lost track of where it was, and now it cannot find its starting point. In this case, the most attractive option is to reformat the hard disk. This action gives the hard drive a new starting point to work from. Unfortunately, it also destroys anything you had stored on the disk. If the reformatting procedure is not successful or the system still won’t boot from the hard drive, you must replace the hard disk drive unit with a working one.
TROUBLESHOOTING CD-ROM DRIVES
The troubleshooting steps for a CD-ROM drive are almost identical to those of an HDD system. The connections and data paths are very similar. Figure 8.9 shows the parts and drivers associated with CD-ROMs. Because the CD-ROM does not appear in the CMOS configuration information, reboot the system and observe the boot-up information that scrolls up the screen. In particular, look for error messages associated with the CD-ROM drive (such as an MSCDEX xxx error).
Windows Checks
In Windows, you can access the CD-ROM through the CD icon in the desktop’s My Computer icon. The CD-ROM drive’s information is contained in the Control Panel’s System icon. The properties of the installed drive are located under the Settings tab. shows a typical set of CD-ROM specifications in Windows. If the correct drivers are not installed, load the correct driver or contact the CD-ROM manufacturer for the correct Windows driver. Check the system for old AUTOEXEC.BAT and CONFIG.SYS files that could contain commands concerning older CD-ROM drives.
CD-ROM Hardware Checks
In most systems, the CD-ROM drive shares a controller or host adapter with the hard disk drive. Therefore, if the hard drive is working and the CD-ROM drive is not, the likelihood that the problem is in the CD-ROM drive is very high. Before entering the system unit, check for simple user problems:
· Is there a CD in the drive?
· Is the label side of the disk facing upward?
· Is the disk a CD-ROM or some other type of CD?
If the CD-ROM drive is inoperable and a CD is locked inside, you should insert a straightened paper clip into the tray-release access hole that’s usually located beside the ejection button. This will release the spring-loaded tray and pop out the disc. If no simple reasons for the problem are apparent, begin by exchanging the CD-ROM drive with a known good one. If the new drive does not work, check the CD-ROM drive’s signal cable for proper connection at both ends. Exchange the signal cable for a known good one.If the controller is built in to the system board and becomes defective, it is still possible to install an IDE host adapter card in an expansion slot and use it without replacing the system board. This action can also be taken to upgrade older IDE systems to EIDE systems so that they can use additional IDE devices. The onboard IDE controller might need to be disabled before the system will address the new host adapter version.
TROUBLESHOOTING PORT PROBLEMS
Figure 8.11 illustrates the components involved in the operation of the serial, parallel, and game ports. Failures in these devices tend to end with poor or no operation of the peripheral. Generally, there are only four possible causes for a problem with a device connected to an I/O port:
· The port is defective.
· The software is not configured properly for the port.
· The connecting signal cable is bad.
· The attached device is not functional.
Port Problem Symptoms
Typical symptoms associated with serial, parallel, or game port failures include
- A 199, 432, or 90x IBM-compatible error code displays on the monitor (Printer Port error).
- The online light is on, but no characters are printed by the printer.
- An 110x IBM-compatible error code displays on the monitor (Serial Port error).
- Device not found error message displays, or you have an unreliable connection.
- Input device does not work on the game port. I/O ports typically do not generate many error messages onscreen.
Basic Port Checks
With newer Pentium systems, you must check the advanced CMOS setup to determine whether the port in question has been enabled, and, if so, whether it has been configured correctly. Check the PC board that contains the I/O port circuitry (and its user guide) for configuration information. This normally involves LPT, COM, and IRQ settings. Occasionally, you must set up hexadecimal addressing for the port addresses; however, this is becoming rare as PnP systems improve. For example, a modern parallel port must be enabled and set to the proper protocol type to operate advanced peripherals. For typical printer operations, the setting can normally be set to SPP mode. However, devices that use the port in a bi-directional manner need to be set to EPP or ECP mode for proper operation. In both cases, the protocol must be set properly for both the port and the device to carry out communications. If serial or parallel port problems are occurring, the CMOS configuration window is the first place to look. Read the port assignments in the boot-up window. If the system has not detected the presence of the port hardware at this stage, none of the more advanced levels will find it either. If values for any of the physical ports installed in the system do not appear in this window, check for improper port configuration. Because the system has not loaded an operating system at the time the configuration window appears, the operating system cannot be a source of port problems at this time. If all configuration settings for the ports appear correct, assume that a hardware problem exists.
Basic Parallel Ports
Run a software diagnostic package to narrow the possible problem causes. This is not normally a problem because port failures do not generally affect the main components of the system. Software diagnostic packages normally require you to place a loopback test plug in the parallel port connector to run tests on the port. The loopback plugs simulate a printer device by redirecting output signals from the port into port input pins. You can use a live printer with the port for testing purposes. However, this action elevates the possibility that the printer might inject a problem into the troubleshooting process. If there is a printer switch box between the computer and the printer, remove the print-sharing equipment, connect the computer directly to the printer, and try to print directly to the device.
T I **Be aware that external printer sharing devices can cause some types of printers to not work.**
Basic Serial Ports
As with parallel ports, diagnostic packages typically ask you to place a serial loopback test plug in the serial port connector to run tests on the port. Use the diagnostic program to determine whether any IRQ or addressing conflicts exist between the serial port and other installed options. The serial loopback plug is physically wired differently from a parallel loopback plug so that it can simulate the operation of a serial device. You can also attach a live serial device to the port for testing purposes but, like the printer, this elevates the possibility that non-port problems can be injected into the troubleshooting process.
Windows Checks
You can reach the I/O port functions in Windows 9x through two avenues: the desktop’s Start/Settings buttons or My Computer icon. Printer port information can be viewed through the Printers icon; serial port information is accessed through the System/Device Manager entries under the Control Panel icon.
Windows 9x Parallel Ports
Check to determine whether the Print option from the application’s File menu is unavailable (gray). If so, check the My Computer/Printers window for correct parallel port settings. Make certain that the correct printer driver is selected for the printer being used. If no printer (or the wrong printer type) is selected, use the Add Printer Wizard to install and set up the desired printer. The system’s printer configuration information is also available through the Device Manager tab under the System icon in the Control Panel. Check this location for printer port setting information. Also, check the definition of the printer under the Control Panel’s Printer icon. Windows 9x comes with an online tool, called Print Troubleshooter, to help solve printing problems. To use the Print Troubleshooter, click the Troubleshooting entry in the Windows 9x Help system, Press F1 to enter the Help system. The Troubleshooter asks a series of questions about the printing setup. After you have answered all of its questions, the Troubleshooter returns a list of recommendations for fixing the problem. If the conclusions of the troubleshooter do not clear up the problem, try printing a document to a file. This enables you to separate the printing software from the port hardware. Continue troubleshooting the port by checking the printer driver to ensure that it is the correct driver and version number. Click the Printer icon and select the Properties entry from the menu. Click the Details tab to view the driver’s name. Click the About entry under the Device Options tab to verify the driver’s version number.Click the printer port in question (under the Printer icon) to open the Print Manager screen. Check the Print Manager for errors that have occurred and that might be holding up the printing of jobs that follow it. If an error is hanging up the print function, highlight the offending job and remove it from the print spool by clicking the Delete Document entry of the Document menu.
Windows 9x Serial Ports
Information on the system’s serial ports is contained in three areas under the Device Manager. These are the Resources entry, the Driver entry, and the Port Settings entry. The Resources entry displays port address ranges and IRQ assignments. The Driver entry displays the names of the installed device drivers and their locations. The Port Settings entry contains speed and character frame information for the serial ports. The Advanced entry under Port Settings enables you to adjust the transmit and receive buffer speeds for better operation. Check under the Windows 9x Control Panel/System/Device Manager window for correct serial port settings. Check for the correct serial port settings under Windows 9x:
1. Click the Port Settings option to see the setup for the ports. Most serial printers use settings of 9600 Baud, No Parity, 8 Bits, 1 Stop Bit, and Hardware Handshaking (Xon-Xoff ).
2. Click the Resources button to determine the IRQ Setup for the port.
3. Check the user’s manual to document the correct settings for the device using the port in question.
USB Port Checks
Because nearly any type of peripheral device can be added to the PC through the USB port, the range of symptoms associated with USB devices can include all the symptoms listed for peripheral devices in this chapter. Therefore, problems associated with USB ports can be addressed in three general areas:
· The USB hardware device
· The USB controller
· The USB drivers
As with other port types, begin troubleshooting USB port problems by checking the CMOS setup screens to make sure that the USB function is enabled there. If it is enabled in CMOS, check in the Windows Control Panel/System/Device Manager to make certain that the USB controller appears there. In Windows 2000, the USB controller should be listed under the Universal Serial Bus Controllers entry or in the Human Interface Devices entry (using the default Devices by Type setting). If the controller does not appear in Device Manager or a yellow warning icon appears next to the controller, the system’s BIOS might be outdated. Contact the BIOS manufacturer for an updated copy of the BIOS. If the controller is present in the Device Manager, right-click the USB controller entry and click the Properties tab. If there are any problems, a message appears in the Device Status window. If the BIOS and controller settings appear to be correct, the next items to check are the USB port drivers. These ports have a separate entry in the Device Manager that you can access by clicking the Universal Serial Bus Controllers option, right-clicking the USB Root Hub entry, and then clicking the Properties tab. If a USB device does not install itself automatically, you might have conflicting drivers loaded for that device and you might need to remove them. To remove potentially conflicting USB drivers,
1. Disconnect any USB devices connected to the system and start the system in Safe mode.
2. Under Windows 2000, you are asked about which operating system to use. Use the up and down arrow keys to highlight Windows 2000 Professional or Windows 2000 Server, and then press Enter. If alert messages appear, read each alert and then click the OK button to close it.
3. Open the Device Manager, click the USB device, and then click the Remove option. Your particular USB device might be listed under the Universal Serial Bus Controller, Other Devices, Unknown Devices, or a particular device category (such as the Modem entry if the device is a USB modem).
4. Click the Start menu, select the Shut Down option followed by the Restart entry, and then click the OK button.
5. Connect the USB device directly to the USB port on your computer. If the system does not auto-detect the device, you must install the drivers manually. You might need drivers from the device manufacturer to perform this installation.
TROUBLESHOOTING MODEMS
A section on troubleshooting modems has to be subdivided into two segments:
· external modems
· internal modems
In the case of an internal modem, you should check it out in the same basic sequence as any other I/O card. First, check the modem’s hardware and software configuration, check the system for conflicts, and check for correct drivers. Improper software setup is the most common cause of modems not working when they are first installed. Inspect any cabling connections to see that they are made correctly and functioning properly, and test the modem’s hardware by substitution. If an external modem is being checked, it must be treated as an external peripheral, with the serial port being treated as a separate I/O port. The Figure below shows the components associated with internal and external modems.
**Be aware of the fact that devices sharing the same resources can lead to failures.**
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| Modem Connected to computer |
Modem Symptoms
Typical symptoms associated with modem failures include the following:
· No response from the modem.
· Modem does not dial out.
· Modem does not connect after number has been dialed.
· Modem does not transmit after making connection with remote unit.
· Cannot get modem installed properly for operation.
· Garbled messages are transmitted.
· Cannot terminate a communication session.
· Cannot transfer files.
COM Port Conflicts
Every COM port on a PC requires an IRQ line in order to signal the processor for attention. In most PC systems, two COM ports share the same IRQ line. The IRQ4 line works for COM1 and COM3, and the IRQ3 line works for COM2 and COM4. This is common in PC compatibles. The technician must make sure that two devices are not set up to use the same IRQ channel. If more than one device is connected to the same IRQ line, a conflict occurs because it is not likely that the interrupt handler software can service both devices. Therefore, the first step to take when installing a modem is to check the system to see how its interrupts and COM ports are allocated. You can alleviate this particular interrupt conflict by using a bus mouse rather than a serial mouse, thus freeing up a COM port. To install a non-PnP device on a specific COM port (that is, COM2), you must first disable that port in the system’s CMOS settings in order to avoid a device conflict. If not, the system might try to allocate that resource to some other device because it has no way of knowing that the non-PnP device requires it.
Windows Modem Checks
In Windows, you can find the modem configuration information in the Control Panel under the Modems icon. Under the icon are two tabs: General and Diagnostics. The Properties button in the General window provides Port and Maximum-Speed settings. The Windows program contains an application called HyperTerminal that can be used to control the operation of the system’s modem with TelNet services. HyperTerminal is capable of operating with several different modem configurations. This flexibility enables it to conduct transfers with a wide variety of other computer systems on the Internet, such as UNIX and Linux, without worrying about operating system differences. Using HyperTerminal with TelNet to access other locations is much quicker than browsing Web sites with a graphical browser. The HyperTerminal New Connections window, provides the options for configuring the communications settings. This program can be accessed through the Start/Programs/ Accessories/Communications path in Windows 98. Windows also provides fundamental troubleshooting information for wide area networking through its system of Help screens. Just select Help from the Control Panel’s toolbar, and click the topic that you are troubleshooting.
Communication Software
All modems require software to control the communication session. This software is typically included with the purchase of the modem and must be configured to operate in the system the modem will be used in. To communicate with other computers, some information about how the communication will proceed must be agreed on. In particular, it is necessary to match the protocol of the remote unit, as well as its parity, character framing, and baud rate settings. In the case of online services, the information comes with the introductory package the user receives when joining the service. At the fundamental instruction level, most modem software employs a set of commands known as the Hayes-compatible command set. This set of commands is named for the Hayes Microcomputer Products company that first defined them. In the Hayes command structure, the operation of the modem shifts back and forth between a Command mode and a Communications mode. In the Command mode, the modem exchanges commands and status information with the host system’s microprocessor. In Communications mode, the modem facilitates sending and receiving data between the local system and a remote system. A short guard
Modem Hardware Checks
Modems have the capability to perform three different kinds of selfdiagnostic tests:
The local digital loopback test
· The local analog loopback test
· The remote digital loopback test
If transmission errors occur frequently, you should use the various loopback tests to locate the source of the problem. Begin by running the remote digital loopback test. If the test runs successfully, the problem is likely to be located in the remote computer.
If the test fails, run the local digital loopback test with self-tests. If the test results are positive, the problem might be located in the local computer. On the other hand, you should run the local analog loopback test if the local digital test fails. If the local analog test fails, the problem is located in the local modem. If the local analog test is successful and problems are occurring, you should run the local analog test on the remote computer. The outcome of this test should pinpoint the problem to the remote computer or the remote modem. If the modem is an internal unit, you can test its hardware by exchanging it with a known good unit. If the telephone line operates correctly with a normal handset, only the modem, its configuration, or the communications software can be causes of problems. If the modem’s software and configuration settings appear correct and problems are occurring, the modem hardware is experiencing a problem and it will be necessary to exchange the modem card for a known good one.With an external modem, you can use the front-panel lights as diagnostic tools to monitor its operation. You can monitor the progress of a call, and its handling, along with any errors that might occur.
TROUBLESHOOTING SOUND CARDS
Some very basic components are involved in the audio output of most computer systems: a sound card, some speakers, the audiorelated software, and the host computer system. Most sound cards perform two separate functions: to play and to record sound files. You might need to troubleshoot problems for either function.
Sound Card Configuration Checks
In the past, sound cards have been notorious for interrupt conflict problems with other devices. Because these conflicts typically exist between peripheral devices, they might not appear during bootup. If the sound card operates correctly except when a printing operation is in progress, for example, an IRQ conflict probably exists between the sound card and the printer port. Similar symptoms would be produced for tape backup operations if the tape drive and the sound card were configured to use the same IRQ channel. Use a software diagnostic program to check the system for interrupt conflicts. Checking the system for resource conflicts in Windows is relatively easy. Access the Control Panel and select the System icon. From this point, click the Device Manager and select the Sound, Video, and Game Controller option. If the system detects any conflicts, it places an exclamation point within a circle on the selected option. From the Device Manager, choose the proper sound card driver from the list and move into its Resource window. The page’s main window displays all the resources the driver is using for the card. The Conflicting Device list window provides information about any conflicting resource that the system has detected in conjunction with the sound card.
If the Windows PnP function is operating properly, you should be able to remove the driver from the system, reboot the computer, and allow the operating system to redetect the sound card and assign new resources to it.
Check to verify that the multimedia icon is installed in the Control Panel and available through the Start/Programs/Accessories path. Also check the Control Panel’s Device Manager to see that the correct audio driver is installed and that its settings match those called for by the sound card manufacturer. If the drivers are missing, or wrong, add them to the system through the Control Panel’s Add/Remove Hardware Wizard. If the driver is not installed or is incorrect, add the correct driver from the Available Drivers list. If the correct driver is not available, reinstall it from the card’s OEM disk or obtain it from the card’s
manufacturer.
Sound Card Hardware Checks
Most of these checks are very simple. They include checking to see that the speakers are plugged in to the speaker port. It is not uncommon for the speakers to be mistakenly plugged in to the card’s MIC (microphone) port. Likewise, if the sound card will not record sound, make certain that the microphone is installed in the proper jack (not the speaker jack) and that it is turned on. Check the amount of disk space on the drive to ensure that there is enough to hold the file being produced. In the case of stereo speaker systems, it is possible to place the speakers on the wrong sides. This will produce a problem when you try to adjust the balance between them. Increasing the volume on the right speaker will instead increase the output of the left speaker. The obvious cure for this problem is to physically switch the positions of the speakers.
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