638 Computer Service and Repair
Troubleshooting Overview
There is no one foolproof method to troubleshooting. There are too many
variables that can cause a computer to fail, but there are recommended
procedures that can be used to help you organize your approach to solving a
computer problem. The causes of failure discussed are not all inclusive and
should be interpreted as a guide to solving a computer-related problem or
complete system failure.
When troubleshooting computer problems, the first thing you must do is
isolate the problem. You must determine if it is a hardware problem, software
problem, or user-generated problem. This is easier said than done. The best way
to go about this is to decide when the problem is occurring. In other words, at
what stage of computer operation is the problem occurring? Did the failure or
problem happen during the POST, during the loading and initialization of the
required operating system files, or after the logon and running the services and
application software? This section discusses the common causes of failure related
to the three stages of computer operation. The first stage is the POST. The second
stage is loading the required operating system files and initializing the hardware
system. The third stage is after the logon. It comprises loading the startup
programs and running applications and services.
First Stage
If the problem occurs during POST, it is most likely a hardware failure. In this
stage, no operating system software or allocation software has been loaded. The
post may fail to complete if a damaged hardware device fails POST or fails its
own diagnostic routine. For example, a telephone modem that has been damaged
during a thunderstorm may cause the computer to lock up during the POST or
immediately after.
If you just built the computer system and it fails to successfully boot the first
time during POST, chances are you have improperly installed the RAM, CPU, or
CPU cooling device. A high-speed CPU that has an improperly installed cooling
fan and heat sink may generate excessive heat in a few seconds, causing the
computer to freeze while performing the POST. Improperly seated RAM may
also cause the computer to fail during POST. When memory is improperly seated,
a beep code typically will be issued, indicating a problem with RAM. Go back
and reinstall these devices and remove all unnecessary devices, such as adapter
cards that are not required for system operation, and reboot the system.
If the problem still persists, you can either substitute parts to determine
which hardware device is causing the failure during POST or use a third-party
utility that uses a POST card to diagnose the POST problem. A very popular
third-party utility suite used by repair centers is PC-Doctor Service Center 6. The
complete PC-Doctor Service 6 kit is shown in Figure 15-1.
The kit includes all the software and hardware you need to perform a
thorough testing of all computer hardware components. PC-Doctor is used
by Circuit City firedog technicians as well as Staples to perform computer
diagnostics in the service department.
The PC-Doctor POST card, Figure 15-2, is inserted into any PCI slot and used
to diagnose errors during POST caused by hardware failure such as the CPU,
RAM, or the motherboard. A POST error code is displayed on the LEDs. The
technician can then match the code to the diagnostic chart in the user manual.