Fault Finding

Get your act together first

Before you attempt any sort of fault finding, you should be sure about a few things:

1)
The first and most important rule is make sure that you know what you are doing. Have a good understanding of what software and hardware the computer you are about to repair contains and how it works.

2)
Make sure you have all the documentation you might need, such as the motherboard manual or drivers installation instructions. If documentation is involved in the fault finding process, make sure you read it carefully. You'd be amazed what you can learn from manuals!

3)
Depending on the nature of the fault, you might need a boot or emergency disk and/or driver and operating system and applications disks. Anti-Virus disks might also be needed.

4)
The most commonly made mistake in fault finding is diving in at the deep end without giving the problem some thought. If you approach your task with a methodical mind you are much more likely to be successful.

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Gathering your clues

Before attempting any diagnostics procedures, especially before opening the cover, ask yourself the following questions:

1)
Are all leads connected properly and are the plugs and fuses OK? The simplest things can have the biggest impacts. Some people can't see the wood for the trees.

2)
Have you checked the system installation? Depending on the fault you might want to have a general look around. Does the Windows Device Manager display anything unusual (wrong device settings, yellow exclamation marks, interrupt conflicts, etc.). The symptoms of a fault might not necessarily lead you directly to its cause.

3)
Have you observed all of the symptoms properly? It is no good to follow the description of a third party alone. So make sure the fault can be reproduced and the symptoms observed. Make notes if you get lots of error messages and references. Some faults are rarer than others, so those notes might also serve you as future reference. If you keep notes of rare faults, don't forget to put down how you solved them. Next time you come across the same situation you might not remember.

4)
Having a general look around the BIOS configuration can also prove very useful.

5)
Ask yourself if there have been any changes to the system lately? Have any new drivers or new adapters been installed? Is there a new program running that might be the cause? Try to establish when the fault first occurred. Any cute little utility can wreck your system, especially if it plays with the registry.

6)
Has anyone else used the system? In a multi-user environment you will find it difficult to establish who did what last, especially when children are involved. But give it a try, every clue is useful Sherlock.

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Just so I've mentioned it!

• Make yourself aware of health and safety procedures
  and follow them!

• Always switch off the power before moving or replacing anything!

• Observe antistatic precautions when handling system components!

If you have to open up the system unit, have a quick look around for any signs of foreign bodies or contamination. Insects crawl through the tiniest gaps and cause fatal errors. Also have a good look if all the sockets and chips are seated correctly.

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The Diagnostics Process

Basically there are three types of diagnostics processes:

• The Power On Self Test (POST)
  That's what the computer does on its own. It checks up on itself and if it finds a problem it informs you of it.

• Routine User diagnostics
  That's the sort of problem that every user can solve on his/her own by following simple steps or by executing standard applications or utilities.

• Advanced User diagnostics
  That's where the trained expert or at least fault literate user comes it.

The Power On Self Test

Whenever the power is switched on or rebooted, the BIOS automatically performs a series of self-tests referred to as POST (Power On Self Test). The system is tested in a specific order that may vary slightly from system to system, but the basic sequence includes the system board, ROM, display memory and major peripherals. If the POST discovers a problem, an error message is generated that may take the form of an audio code (series of beeps) and/or a visual message that appears on the screen. 

Most BIOSes run more than 30 individual steps during the POST, including initialization of peripherals, displaying BIOS information on the monitor and a final beep to show that all is well (two beeps on some systems). You can see and hear these processes to some extent by observing the system as it boots. Memory counts will appear on the screen, LEDs will flash, drives will come to life for a short time, and beeps will be heard, all indicating that test are underway.

Routine User Diagnostics

Routine-user diagnostics can be defined as those diagnostics that be carried out be experienced and non-experienced users alike. These can consist by running a range of programs, some of which will come with the operating system, or alternatively can be purchased from software vendors at an affordable price. Examples of these diagnostics are the SCANDISK utility of Windows 95/98 or programs like FIRST AID.

Dealing with typical faults and error messages are also part of the routine user diagnostics process. The error message that is displayed when you leave a non-system floppy disk in the drive at boot up is a typical example.

Advanced User Diagnostics

Advanced user diagnostics are all the tasks that require knowledge of special commands, software or hardware tools. The fixed disk utility or the registry editor for example are programs you want your granny to try out. Many of the advanced diagnostic programs available go beyond what is considered to be purely diagnosis though. Most third party packages also provide repair, recovery and benchmarking options, and, although available to anyone, are really aimed at the level of the technician.

The tools used for advanced work can be divided into three main areas:

• Service and maintenance manuals
  Don't think manuals are only for those who don't know what they are doing. Service manuals are a useful aid to the routine user and experienced technician alike in providing a vast amount of technical information, and often diagnostic tools.
  

• Advanced diagnostic utilities
  Not all utilities available for advanced users are complex or expensive. Most of the utilities available will not only permit you access to the inner workings of your system, but also permit you to make major changes to disk contents, system configuration and more. Always be careful when using advanced diagnostics tools, as they allow modifications to be made to such an extent that the system may not recover. On a more positive note, advanced diagnostic software utilities can very often be invaluable when it comes to recovering from a major malfunction within the system, and are certainly very interesting to use. Norton Utilities is a typical example. ALWAYS make sure that the version you use is FULLY compatible with the version of your operating system though, incompatibilities at this level can have fatal consequences.
  

• Hardware tools and add-in devices.
  Hardware tools and add-in devices include 'multi meters' for checking voltages, resistance, etc. and 'POST cards', adapter cards that plug into an expansion slot and deliver advanced readings about the targeted hardware.

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Emergency Disks

In DOS you can create a system disk by typing the command SYS at the prompt. In Windows 95/98 you have to use the STARTUP DISK tab of the ADD/REMOVE PROGRAMS dialog box of the CONTROL PANEL (you'll need your Windows installation CD for this).

Whichever way you create your startup disk, it will always contain the minimum files needed to start up your system in the event of a hard disk drive failure. However, it will only get you as far as the command prompt, so if you are using DOS you will need to copy at least some utilities to your startup disk manually if you want to get some use out of it, such as: EDIT.COM, FORMAT.COM, FDISK.COM, SYS.COM, etc. The table below lists the files contained on your startup disk. Files marked with an asterisk (*) are hidden files.

Notice that the Windows 98 startup disk includes CD ROM support for the first time. In order to upgrade your DOS or Windows 95 startup disk for CD ROM support you need to do the following steps manually:

1. Create your start up disk in Windows 95 as described above

2. Copy the file MSCDEX.EXE from your WINDOWS\COMMAND directory onto your start up disk.

3. On your CD ROM driver installation disk, find the file with the extension .SYS and copy it onto your startup disk. The file is normally called something like: CDROM.SYS 

4. Using Windows Notepad, open the AUTOEXEC.BAT file on your startup disk, and add the following line: A:\MSCDEX.EXE /D:CD001 /L:D /V

5. Using Windows Notepad, open the CONFIG.SYS file on your startup disk, and add the following line: DEVICE=A:\CDROM.SYS /D:CD001 /V