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. As previously indicated, these components include the drive, its signal cable, and the HDC. Like the FDC from the floppy disk drive, the HDC can be mounted on an adapter card, or it can be integrated into the system board. Normally, you must remove the outer cover form the computer to troubleshoot these components.

In a pre-Pentium system, the easiest component to check is the controller card that holds the HDD interface circuitry. Exchange the controller card with a known good one of the same type. Make certain to mark all the cards control signal cables before disconnecting them. Also, identify their connection points and direction. Your makings help to ensure their proper re-installation. Reconnect the disk drive signal cables to the new controller card.

Try to reboot the system from the hard drive. If the system boots up properly, check to see that all the DOS commands are working properly. Also, check the operation of all the hard disks software programs to make sure they are still functioning correctly. Reinstall any program that does not function properly.

The next logical step may seem to be to replace the hard drive unit. However, it is quite possible that the hard drive may not have any real damage. It may just have 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 that you had on the disk before you replace it may save the expense of buying a new hard disk drive that is not needed. Make certain to use the /S modifier, or repeat the SYS C: operation with the FORMAT command, to restore the system files to the hard drive..

If not, check the HDD signal cable for proper connection at both ends. Exchange the signal cables for a known good one. Check the HDD Drive select jumper and Master/Slave/Single jumper settings to make sure they are set correctly, as illustrated. Check to see whether the system might be using the cable select option also depicted. This setting requires a special CSEL signal cable designed to determine the master/slave arrangements for multiple IDE drives. Exchange the HDD power connector with another one from the power supply, to make certain that it is not a source of problems.

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BASIC HDD Checks

If the HDD configuration information is correct and you suspect a hard disk drive problem, the first task is to determine how extensive the HDD problem is place a clean boot disk in the A: Drive and try to boot the system. Then, execute a DOS 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 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 may also be produced by this condition

If the clean boot disk has a copy of the FDISK program on it, attempt to restore the drives master boot record by typing the following:

A>FDISK /MBR

Providing that the hard disk can be accessed with DIR command, type and enter the following command at the DOS prompt

SYS C:

This command copies the IO.SYS, MSDOS.SYS, and COMMAND.COM system files from the DOS disk to the hard disk drive. Turn off the system, remove the DOS disk from the A: drive,and try to reboot the system from the hard drive.

If the system boots up properly, check to see that the operating system commands are functioning properly. Also, check to see that all installed software programs function properly. Recheck the installation instructions  of any program that does not function properly. Reinstall the software program if necessary.

Actually, three conditions produce a Bad or Missing COMMAND.COM error message. These conditions include the following:

* The first condition occurs when the COMMAND.COM file cannot be found on the hard drive, and no bootable disk is present in the A:drive

* The COMMAND.COM file is not located int he hard drives root directory. This message is likely when installing a brand new hard drive or a new DOS version.

* The message also occurs if the user inadvertently erases the COMMAND.COM file from the root directory of the hard drive.

If the system cannot see the drive after booting to the floppy disk drive, an Invalid Drive message or an Invalid Drive Specification message should be returned in response to any attempt to access the drive. Under these conditions, you must examine the complete HDD system. Use the FDISK utility to partition the drive. Next, use the FORMAT/S command to make the disk bootable. Any data that was on the drive will be lost in the formatting process, But it was already gone because the system could not see the drive.

Attempt to run a diagnostic software program, if possible, Try to use a diagnostic programs HDD Tests, and perform the equivalent of the All Tests function.

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HDD Configuration Checks

While booting up the system, observe the BIOS's HDD type information displayed on the monitor. Note the type of HHD that the BIOS believes is installed in the system. The values stored in the CMOS memory must accurately reflect the actual HDDs 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. You can access these values for change by pressing the Ctrl and Del key simultaneously, during the bootup procedure.

If the HDD is used with a system board mounted controller, check for the presence of an HDD enabling jumper on the system board. Make certain that it is set to enable the drive, if present. Check the drive to make sure that it is properly terminated. Every drive type requires a terminating block somewhere in the interface. On system level drives, check the master slave jumper setting to make sure that it is set properly for the drives logical position in the system.

If you have more than one device attached to a single interface cable, make sure that they are of the same type. Mixing 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 may 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 results in the system not being able to see the drive.Also check the CMOS setup utility to make sure that SCSI support has been enabled, Along with large SCSI drive support.

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HARD DISK DRIVE PROBLEMS

Typical symptoms associated with hard disk drive (HDD) failures include the following:

* The computer does not boot up when turned on.
* The computer boots up to a sysmtem disk in the A: drive, but not to the hard drive, indicating that the systme files on the HDD are mising or have become corrupt.
* No motor sounds are produced by the HDD while the computer is running.
* An IBM compatible 17xx error code is produced on the monitor screen.
* An HDD Controller Filure message displays, indicating a failure to verify hard disk setup by system configuration file error.
* A C: or D: Fixed Disk Drive Error message display, 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 HDDs activity light remains on and no boot up occurs, indicating that the HDDs 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, a Hard Drive Boot Failure, or an Invalid Drive or Drive Specification message displays, indicating that the disks master boot record is missing or has become corrupt.
* A No ROM BASIC System Haltedd, or ROM BASIC Interpreter Not Found Message displays, followed by the system stopping, indicating that no master bot record was found in the system. This message is produced only by PCs, XTs, and osme clones.
* A current drive no longer valid message displays, indicating that the HDDs CMOS configuration information is incorrect or has become corrupt.

HDD Configuration Checks
BASIC HDD Checks
HDD Hardware Checks

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Monitor Problems Toubleshooting

All the circuitry discussed so far is part of the computer or its video adapter unit. The circuitry inside the monitor is responsible for accepting, amplifying, and routing the video and synchronizing information to the CRT's electron guns and the deflection coils.

Monitor Handling
Show in figure, Components located inside a typical CRT (Cathode Ray Tube) 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.

Operation of a monitor with the cover removed poses a shock hazard from the power supply. Therefore, any one unfamiliar with the safety precautions associated with high voltage equipment should not attempt servicing.

The high voltage levels 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. Due to the high voltage levels, you should never wear antistatic grounding straps when working inside the monitor.

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 tubes 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 googles when handling picture tubes.

Color monitors produce 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 monitors housing.

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Mouse Problems Troubleshooting

The levels of mouse troubleshooting move from configuration problems to software problems including command line, windows, and applications to hardware problems.
Maintenance of the mouse if fairly simple. Most of the problems 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 latching mechanism on it bottom. Twisting the latch counter clockwise enables you to remove the trackball. Then you can clean dirt out of the mouse.

Basic Mouse 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 displays This action starts the operationg system with the most basic mouse driver available.

If the mouse will not operate in safemode, restart the system and check the CMOS setup screen during boot up for the presence of the serial port that the mouse is connected to.

If the mouse work 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 window control panel. Consult the device manager entry under the control panels system icon. Select the ports option, click the COMs 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. Move to the resources tab 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 the 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 manufacturers driver disk in the CD/DVD Drive and load it using the other mouse. If the OEM driver fails to operate the mouse in windows, contact the mouse manufacturer for an updated windows driver. windows normally supports only mice 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 AUOTEXEC.BAT and CONFIG.SYS files that may contain conflicting device drivers. Two common driver files may 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

If the 2/3 button switch and driver setup is correct, you must divide the port circuitry in half. For most systems, this involves isolating the mouse from the serial port. 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 may 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.

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Keyboard Problems Troubleshooting

Most of the circuitry associated with the computers 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.

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 6 short beeps is produced during boot up.
* Wrong characters display.
* An IBM compatible 301 error code displays.

Basic Keyboard Checks

Keyboard information is stored in the CMOS setup memory, and must accurately reflect the configuration of the system; otherwise, an error occurs. In most CMOS screens, the setup information includes keyboard enabling, Numlock key condition at startup, typematic rate, and typematic delay. The typematic information applies to the keyboars capability to repeat characters when the key is held down. The typematic rate determines how quickly characters are repeated, and the delay time defines the amount of time the key can be held before typematic action occurs. A typical typematic rate setting is 6 characters per second; the delay is normally set at 250 milliseconds.

As with other components, the only time a configuration problem is likely to occur is when the system is being set up for the first time or when a new option is installed. The other condition that cusses a configuration problem involves the system boards CMOS backup battery. If the battery fails, or has been changed, the contents of the CMOS setup will be lost. After replacing the battery, you must always run the setup utility to reconfigure the system.

Turn on the system and observe the BIOS screens as the system boots up. Note the keyboard type listed in the BIOS summary table. If possible, run a selected diagnostic program to test the keyboard. Run the programs keyboard test function, and perform the equivalent of the All test function if available. These test are normally very good at testing the keyboard for general operation and sticking keys.

If the keyboard produces odd characters on the display, check the windows keyboard settings in the control panel 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 panels keyboard icon.

Keyboard Hardware checks

If you suspect a hardware problem, you must first isolate the keyboard as the definite source of the problem. Because the keyboard is external to the system unit, detachable, and inexpensive, begin by exchanging the keyboard with a good keyboard. If the new keyboard works correctly, return the system to full service and service the defective keyboard appropriately.

To service a defective keyboard remove the back cover of the keyboard and check for the presence of a fuse in the +5v (DC) supply and check it for continuity. 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, Just replace it with a fuse of the same type and rating.

If the system still wont boot up. recheck the CMOS setup to make sure that the keyboard is enabled. Check the keyboard cabling for continuity. And, finally, check the video display system (monitor and adapter card) to make sure that it is functional.

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