DIY Computers


DIY Computer Repairs   Post Beep Codes   Using a Postcard    Boot Diagnostic Flowchart

Repairing your Computer

Diagnosing a fault and repairing a computer yourself is a skill that comes with practice. A computer that will not boot at all is generally easier to troubleshoot than one that fails only intermittantly during operation. In this section we will discuss a few of the different methods used to determine which component is faulty.

Troubleshooting computers has become easier with the advent of broadband internet connection. The world wide web has become a good source of information and tips on how to effectively and efficiently troubleshoot computers and other gadgets. Because of this benefit, you can eliminate the hassle of hiring computer technicians and other professionals. Arm yourself with the necessary skills by reading this article.

Troubleshooting a computer that will not boot

Troubleshooting a computer that will not start up is arguably the easiest to diagnose as once the faulty component is identified and replaced the machine will then boot, allowing us to know immediately if we were successfull or not. We have prepared a flowchart for reference during the troubleshooting process described below. When following the steps below never unplug or plug in a device or peripheral while the machine is on. Always turn the power off before removing or adding components.

  1. Inspect the components inside the case, do you see any burn marks and are there any nasty smells coming from anything? Are the capacitors on the mainboard still cylindrical or are the bubbled up? Sometimes the memory on a computer may need reseating, simply remove it from its slot and re-insert it. It may not be sitting on its contacts correctly or dust may be reducing the connections effectiveness. This is common particularly after the machine has been transported or bumped. If this quick and easy fix doesnt resolve the problem then read on.
  2. With the sidecovers removed turn the power switch on. Do the power supply and CPU cooler fans turn? If they do proceed to the next step. If they dont replace the power supply and try again. Does the machine boot? If no check the power switch is working properly and short the pins out on the mainboard for the power switch for a second or so the simulate the power switch. If the machine still does not boot proceed to the next step but keep the new power supply connected to the machine while doing the following tests so that it is a known good one and can be discounted as defective.
  3. When a machine starts up it usually will beep once to indicate it has passed all of its start up tests and is ready to proceed. If any of these tests fail most computers will beep in a preset pattern giving some indication of the fault. If the machine gives a string of beeps identify your BIOS manufacturer and see Post Beep Codes. This list of codes will give an indication of which component is faulty. If the computer does not beep or you cannot identify the beep code proceed to the next step.
  4. Use a post card to diagnose the fault. A Power On Self Test Card is plugged into a PCI, ISA or PCI Express slot and provides a fault code that can pinpoint the problem. See Using a Postcard for a more through description.
  5. If the post card does not assist you unplug all the peripheral components of the machine (eg hard drives, optical drives etc) leaving only the barest minimum components required for the machine to start up, those being the PSU, CPU, motherboard and memory. Power the machine up and see if it starts (it will give the single post beep and put the bios startup screen on the monitor). If it starts then turn the machine off and add one peripheral at a time and attempt to start the machine until the faulty peripheral is identified. Bear in mind when doing this that Hard Disk drives do not like being turned off without being parked so they should be left until last. If it does not start does it now give a post beep code? If no try the post card again to see if it gives a usefull error code.
  6. If the machine still doesnt boot you have at this point narrowed it down to three components, the CPU, motherboard or RAM. If replacing the RAM does not rectify the problem the most likely suspect is the motherboard at this point. A motherboard that does not give any sort of post error is most likely defective and the process of elimination we have used to this point would lead to this conclusion, though it does not effectively discount a bad CPU. CPU's also tend to have longer lifespans than motherboards. Replacing the CPU is easier than replacing the motherboard so if you have a compatible one available take the oportunity to swap them over and see what happens.

Troubleshooting a computer that intermittantly fails

Troubleshooting a machine that fails intermittantly during operation can be quite challenging as there are more factors to be considered when diagnosing the problem. The main issue to consider is that the hardwared of the computer may be quite healthy but the software, particularly the operating system and programs, may be corrupt in some fashion causing the machine to crash. The very first thing to consider when a computer spontaneously reboots, locks up or blue screens is what programs were in use and what was running on the computer at the time. Does the computer spontaneously restart only when you play a particular game or use a particular program? Try to find a patch for the game or update to a later version of the program and see if it resolves the problem. Games can be challenging as operating systems evolve over time and running a game for an early version of windows as an example can be impossible or painfull on a recent version.

If you suspect a hardware problem rather than a software problem is causing your machine to misbehave then read on.

When the machine misbehaves what does it do? Does it switch itself off and can it be restarted immediately? This can be a power supply failing or mainboard issues. Does it start afterwards perfectly every time or does it freeze and need a few attempts before it has started effectively. Does it beep (see Post Beep Codes)?

Most intermittant PC hardware problems tend to be either the memory, mainboard or the hard disk drive getting ready to fail. One must also be aware that an overheating CPU can cause the machine to misbehave and this can be easy to resolve, simply clean the CPU cooler to remove the heat trapping dust and check that the CPU cooler fan is turning at an adequate speed. When the machine is running gently touch the heatsink, if it burns you then it is overheating. Those who wish to avoid minor burns might prefer to enter the machines BIOS and look at the CPU temperature there. Many motherboard manufacturers now include programs that allow you to see the CPU temperature and other information from within the operating system. Looking at the operating systems logs to see if there were any software problems at the time of the lockup or reboot can be of great benefit and of course any error messages on the screen can be very usefull. If the meaning of the error is not immediately obvious use google to search for the exact words of the message.

Once you have discounted the more obvious then the next step is to run diagnostic programs on the computer. There are many such programs available on the internet and they are designed to test components such as memory and hard drives. The Ultimate Boot CD is a prime example of a free set of tools you can download off the internet and burn to a cd. The computer is then booted off the CD and you are then presented with a menu allowing you to choose from the different tests available. Run the test specific to the component you suspect is faulty, although most hardware tests arent 100% definitive particularly with intermittant problems they can be usefull for finding components that are obviously near the point of failure.

If running diagnostic tests prove fruitless process of elimination by systematicly replacing components that are suspect can be of benefit. Most lockup or reboot problems are generally either the motherboard, memory or hard disk drive. The memory is usually a great place to start.