|OddMix COMPUTERS - POWER|
Personal Computer PC Power Supply Maintenance
|Picture 1. Power supply overview|
Personal Computer [PC] power supplies are taken for granted. Most casual users are not even aware that they have them. But a neglected power supply can destroy an otherwise perfectly good computer in a surprisingly small time. Maybe it is time to look into this subject from the prevention prospective.
The purpose of the computer power supply is to provide clean, regulated power to different parts of the computer system. Some of the PC's main power users require different voltages and currents in various degrees of smoothness or regulation. Until 1980 almost all of the regulated power supplies used to be analog types. These type of power supplies are usually connect to the main power source via a transformer, and has great regulation and not so great efficiencies. They are easy to design, cheap to build, and provide high isolation from the AC [Alternating Current] line voltage. Isolation provides good user protection to prevent electrical shocks.
Once switching regulator components became inexpensive and widely available, engineers redesigned power supplies completely. The large heavy, bulky and expensive line transformers disappeared, along with the 60 Hertz operating frequency. Modern day power supplies connect to the input voltage via a rectifier and capacitor. The AC line voltage thus converted to DC [Direct Current] is chopped up by a power oscillator circuit, running at much higher than 60 Hz line frequency. The higher operating frequency allows the use of smaller cheaper components, smaller power supply size and a lot higher overall efficiency.
|Picture 2. Dust on power supply - closeup|
Luckily removal is a relatively simple affair. All it requires is a soft brush and a vacuum cleaner. In most cases power supply disassembly is not required. Brush anything within reach and the fan blades while vacuum. A can of "canned air" compressed gas can also be very useful, especially if it has a thin plastic tubing. With the tubing inserted into the power supply housing, lots of dust can be loosened up and vacuumed away. Repeat the insertion into as many different places as possible, and repeat the procedure. This "canned air" is really liquified gas. It costs around a few dollars a can and by the time cleaning is done, the can is usually history.
For that reason alone, it may be better to do a more thorough job. Make sure, the power line is disconnected, then carefully remove the power supply cover. It may be required to remove the power supply unit from the computer case. It will all depend on the computers construction. Carefully remove and save all screws and remove the sheet metal housing. Spend a minute or two just to admire the view. Note it if there are any burn marks, or if out of character, tell-tale signs are in evidence of impending disasters. Items like browned resistors, or printed wire boards are worth discovering. Changing charred resistors are a whole lot less expensive now than when it finally fails.
|Picture 3. Power transistor mounting screw|
|Picture 4. Transistor mounting screws|
|Picture 5. Mounting screw location|
Another extremely important maintenance item inside the power supply enclosure is the fan. Fans vary an amazing degree in quality. Underpowered power supplies usually have inferior fans which do not last long. Most fans do not have ball bearings. All bearings require a small amount of light grade oil periodically. Never reassemble an opened up power supply without lubricating the cooling fan. Good choice of lubricant is electric motor oil or sewing machine oil. Do not over oil. It may be necessary to remove the adhesive covered label from the fan's hub to uncover the bearings.
After the fan is lubricated, inspect everything very carefully. If all is in order, then reassemble all components reversing all earlier steps. Reattach the power supply to the computer's housing, and reconnect all cables to their proper places. Make sure all hard drives, CD, DVD and floppy drives are all properly plugged in, then close up the computer. Reconnect the line cord power cable and start the computer. Hopefully all is connected properly and up starts a freshly serviced, more reliable computer.
The cleaning procedure is a good preventive against thermally induced power supply failures. If a computer is operated in a forced hot air heated house, or in equally or more dusty environments, it would be necessary to check the condition of the inside of the computer and the power supply unit more often. A simple check with a flashlight would be all that is necessary to determine if a repeat cleaning would require.