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COMPUTER HARDWARE: POWER SUPPLY & CASES.pptx
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- 2. HISTORY The powersupply industry dates back to the early 1920s, when crude devices were first developed to serve as "B" battery eliminators to power radios in both the commercial and consumer markets. The market for separate power supplies evaporated around 1929, when most radios manufactured included a built-in power supply. The need for stand-alone power supplies remained relatively small in the 1930s and into the 1940s. The dominant technology during this period consisted of vacuum tube linear regulators.
- 3. POWER SUPPLY Powersupplies used vacuum tubes for both the power and control elements. Typically, a voltage regulator (VR) tube, the predecessor to today's zener diodes, was used to produce a stable reference. Control was pretty much limited to the manual twisting of knobs. In those days we did not care too much about dissipation. Under normal circumstances, vacuum tubes ran pretty hot -- and unless the plate of the tubes glowed red, or glass started to melt, no one worried much about it.
- 4. POWER SUPPLY Thesource is the origin of incoming electricity. In most cases, the electricity source is an outlet, battery, or generator. The power supply works to convert the power from the source into the correct format and voltage. Because a variety of options exist, the specific power supply function depends on whether it needs to regulate energy or convert power.
- 5. PURPOSE/IMPORTANCE A powersupply converts the alternating high voltage current (AC) into direct current (DC), and they also regulate the DC output voltage to the fine tolerances required for modern computing components. It powers all the components in your PC, and a bad or faulty one can bring everything down
- 6. PARTS OF POWERSUPPLY Transformer: The transformer changes the incoming voltage to the needed outgoing voltage level. These devices may step up or step down the voltage. Typically, the DC voltage required is much less than the incoming AC voltage from the primary power source. Rectifier: To convert the incoming power from AC to DC, the power supply uses a rectifier, which may be half-wave, full-wave, or bridge. Filter: When AC power changes to DC, it still has distinct waves that need smoothing out. The filter does not completely smooth out the waves to nothing, but it does reduce them considerably. The output from this part is unregulated power. Regulator: A voltage regulator reduces the ripple voltages left by the filter, getting rid of any voltage surges or drops that could damage devices plugged into the power supply.
- 7. How It Works The power supply takes electricity from the wall outlet and transforms it into the kind of electricity that the motherboard and other internal components use. The computer’s power supply converts AC to low-voltage DC that is then portioned out to the internal devices. Be careful never to open the power supply itself as the capacitors inside can store a dangerous electrical charge.
- 8. How It Works Power supplies have essential functions found in all models with additional operations added depending on the device type. Power supplies may need to change voltage up or down, convert power to direct current, or regulate power for smoother outcoming voltage. These functions will help you choose which supply you need for your electrical needs. Getting a device with too many features could cost you more money than you need to spend, but if you don’t get the features you require, you could damage the devices you need to power.
- 9. INSTALLING, MAINTAINING ANDTROULESHOOTING POWER SUPPLIES Power supplies connect to the PC case via four screws mounted in the rear of the case. Unscrew the four screws and the power supply will lift out. As ATX power supplies are always on, be sure to unplug it from the wall outlet before working on it. Adequate cooling is important to prevent damage to the computer’s internal components. The fan inside the power supply itself cools the voltage regulator circuits within the power supply and provides a constant flow of outside air throughout the interior of the computer case. If the fan is not working, turn the computer off before you experience equipment failure. Some power supplies regulate airflow by using a sensor, with a three- wire connector that plugs into the motherboard.
- 10. INSTALLING, MAINTAINING ANDTROULESHOOTING POWER SUPPLIES To improve cooling, most cases come with a case fan. If the case does not have one, you should add one. Most case fans use standard Molex connectors, but some use a special three-pronged power connector that plugs directly into the motherboard. To enable the fans to create airflow, the case needs to be closed. If slot covers are left off empty expansion bays, it can cause the computer to overheat. Slot covers also help keep dust and smoke out of the case. Beware of “great deals” on cases that come with power supplies, as the included power supply is often substandard. Electrical problems range from irregular AC to dying or faulty power supplies. Power supplies may fail suddenly or slowly over time. After you make sure that the wall outlet is providing electricity, checking voltages from the power supply with a voltmeter is the best way to verify that the power supply is working or has failed. A power supply is functioning properly if the output voltages are within 10 percent over or under the expected voltage. Be sure to check all the connections on the power supply. If you determine that it is bad, the most economical solution is to throw it away and replace it with a new one.
- 11. INSTALLING, MAINTAINING ANDTROULESHOOTING POWER SUPPLIES Power supplies will not start unless they are connected to a motherboard. If you need to test a power supply but don’t have a motherboard, use an ATX tester. If one of the internal electrical components in the power supply begins to fail, the result is usually intermittent problems, making it difficult to diagnose. If you are experiencing intermittent problems, such as lockups or different error codes that disappear after rebooting, suspect the power supply. Unfortunately, the voltmeter is not good for diagnosing intermittent problems. Since power supply failures rank second behind floppy drive failures, it is a good idea to keep power supplies in stock for swapping and testing.
- 12. INSTALLING, MAINTAINING ANDTROULESHOOTING POWER SUPPLIES Never open a power supply, even to check the fuse, because the unit contains capacitors that carry high voltage charges that can hurt you. Every PC workbench should have a Class C fire extinguisher handy in case of an electrical fire. Although some fire extinguishers are multi-class, handling all types of fire, use only a Class C fire extinguisher on your PC.
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