Trouble-shooting procedures

It is important that people who have a computer, or are responsible for the care of computers, can diagnose simple hardware and software problems and provide solutions to correct the problems. To do this you must have an understanding of the hardware and software interrelationships so as the problem can be eventually identified. In many cases, a hardware problem appears to manifest itself as a software problem and vise versa. Often, the hardware vendors will blame the software vendors and the software vendors blame the hardware vendors. This leaves the owner of the computer in a predicament as the problem cannot be solved.

Case Study.

Windows 98 could not be installed on a computer with a Cyrix 233mhz processor. Slowing the processor down to 200mhz solved the problem in the short term. The problem actually lay with the BIOS on the motherboard. It needed to be upgraded to take account of the clock speed of the Cyrix processor and the differences between windows 95 and windows 98. So the problem was in the software (BIOS) that controlled the hardware (motherboard) so as the new software (Windows 98) would work with the new hardware (233mh processor).

How to find a simple fault.

There are a few simple rules to fixing a computer that appears not to be working.

1. Check all of the plugs and leads. Make sure that power is actually getting to the part that does not appear to be going. Make sure that the faulty part is plugged in properly and into the correct socket. If necessary, move the computer to a place where you are certain another computer is working.
2. If a certain part is not working, replace it with a part that you know does work. If the new part also does not work, you know that is not the problem and so you need to look further. If everything now works you have found the fault. Replace the part or see (3) below.
3. The problem may be with the software and not the hardware. Put the suspected faulty part into a computer that is the same and see if it works. If not, replace the part.
4. Call a qualified technician to fix the problem.

Some common faults and solutions.

No power on startup

• Not plugged in properly
• No power at the wall plug

Monitor not functioning

• Someone has fiddled with the brightness and contrast control
• The leads are not connected properly
• Someone has bent the pins on the lead
• The video card is faulty

Hard Drive Failure

• The internal battery is flat and the setup information has been lost or changed
• Someone has formatted the hard disk drive
• The lead connecting the HDD to the controller have fallen out.
• The motherboard is faulty

Floppy Drive failure

• The read/write heads are dirty
• Someone has caught a disk inside and the metal part are still in there.
• Someone has caught a disk inside and the read/write heads have been damaged

Won't print

• The leads are not connected properly
• The printer drivers have been deleted or changed
• The printer is not turned on
• The printer is out of ink or is out of paper

Won't connect to network

• The network lead is disconnected, damaged or not connecting through the port
• The network software is damaged or has been changed.
• The configuration on the network card has been changed.

The diagnosis of faulty computers is a very specialized job and requires a large amount of training and experience. For the purpose of this course, basic common sense should prevail and the repair of faulty computers should not extend beyond simple diagnostics and the replacement of peripherals to test the functionality of the suspected component.

Further information on the diagnosis of faults and the repair of these is found in books specifically written for the type of computers being worked on. (PC hardware fault finding Ganly & Cranswick)

Mike Leishman