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Diagnostic Hardware

While not as commonly used as diagnostic software, there are available several pieces of hardware that can be very helpful in troubleshooting some specific hardware problems. These units are not nearly as popular because they are usually more expensive and are used for specific types of problems, making them less universally applicable than the general software utilities that are widely encountered.

If you are a serious home builder or troubleshooter, you may want to consider one or more of the following:

• Loop-Back Plugs: These are small plugs that go onto the serial and parallel ports on your computer and connect the receive to transmit lines to simulate a connection (they connect the port to itself). Using these with a program like Norton Diagnostics allows for full testing of the operation of these ports, whereas without them only the internal portions of the port can be tested.

Note: The type of plugs used by a particular diagnostic utility may be different than the type used by another program made by another company. Check it out before you buy.

• Multimeter/Ohmmeter: An ohmmeter is a device that measures electrical resistance; a multimeter can measure resistance, voltage and current. These devices are used by electricians, electronics designers and repairpeople. They have come down greatly in price and simple ones can be had inexpensively (while top-end ones of course are still quite a bit of money). A simple ohmmeter is useful primarily for checking for short circuits or open circuits (broken connections, damaged cables, etc.) Multimeters can be used for more extensive electronics testing.
• BIOS POST Cards: It is well-known that the BIOS will, if it finds a problem during its power-on self-test (POST), produce audio "beep codes" and/or video messages that indicate what the trouble is that it found. What many do not realize is that the BIOS of most PCs is designed to send a stream of test codes to a special memory location as it performs its tests, usually 80h. By using a special card designed to capture and display these codes, you can pinpoint exactly where in the power-on self-test a system is hanging up. This can be extremely helpful in debugging very stubborn systems. Scott Wainner has more about one of these cards on his site.
• Test Bed: Some experienced PC repair people keep around an older system that they can use as a test bed for components. It can be very useful to be able to test an unknown device with other components that are known to work, to cut down on the guesswork.

There is also more advanced test hardware available, including devices such as logic probes, oscilloscopes, and many types of specialized component testers. These items are generally very expensive and require specific training to be used properly; they are not for the home PC user or even for most hobbyists. Professional test hardware costs thousands of dollars, which is one reason why doing it yourself is often not an option for many kinds of repairs.

Next: The PC Tool Kit

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