1. Power Supplies More details about the source of your computers power…

2. Power Supplies Power Supply Unit (PSU) 1.What is the job of a computer power supply? 2.How are computer power supplies rated? 3.What are the different types of power supplies used in desktop computers (form factors)? 4.What are the names of the connectors on a power supply? 5.What do the color of the wires mean? 6.How do you test a computer power supply?

3. Won’t any power supply do? Power supplies are often overlooked when building a computer system. A poor quality PSU can greatly reduce the life span of a good system or cause instability. A high quality PSU can help reduce the noise or heat generated within a computer system.

4. What do they do? Convert the AC line voltage to a regulated DC voltage that can be used by the computer components Most power supplies conform to the ATX standard and are triggered by a signal from the mother board to turn on They also provide standby power to the motherboard and other peripherals

5. Rating your power supply Wattage: this must be larger than your system requirements Maximum Wattage is the total power for continuous use vs. Peak Wattage which is instantaneous Wattage ratings are self regulated so some manufacturers claim more than what is actually provided

6. Rating continued… Noise – both physical and electrical Electrical noise is variation in the voltage this is reduced/eliminated by the regulator circuit Regulators are mostly switching types and are rated by “ripple voltage” levels (smaller is better) Physical noise is caused by fans that cool the PSU A larger fan will run slower and make less noise, you can get temperature controlled fans, or some units are fan-less (silent)

7. MTBF: Mean Time Between Failures This rates the estimated usage time before the unit fails. 50% will last longer, but 50% will not last as long A 20,000 hour rating is roughly 2.25 years of continuous usage

8. Power Efficiency Power supplies convert high voltage from the outlet to a lower voltage used by the PC During this process some power is lost as heat The more efficient the power supply the less money it will cost to run the PC Look for the 80Plus Logo 80 PLUS Certification115V Internal Non-Redundant % of Rated Load20%50%100% 80 PLUS80% 80 PLUS Bronze82%85%82% 80 PLUS Silver85%88%85% 80 PLUS Gold87%90%87% 80 PLUS Platinum90%92%89% 80 PLUS Titanium92%94%90%

9. Power Supply Form Factors IBM PCATATX ATX12V LaptopTFX12V

10. What are the outputs?

11. What do the colors mean?

12. How do you test a power supply? With a technicians friend (i.e. a paper clip) and a digital multimeter

13. Or more accurately with a Power Supply Tester

14. Test your knowledge: Find two comparable power supplies (PSU) for sale on a reputable website. List the specifications for each PSU Compare the two supplies Determine which power supply is the best and justify your answer.