Introduction to Computers Power Supplies

Different Types of Power Supplies Form Factor ATX, Micro ATX, Mini ITX ATX is larger and provide more power, Micro ATX and Mini ITX are smaller and provide less power Modularity Modular, Semi Modular, Non Modular Modular is the most expensive, but also the most customizable and best for cable management Wattage Wattage is based on your computer’s needs. Most computers will be fine with under 500 watts, but computers with multiple hard drives, optical drives and power video cards will need more power

Wire bundle - Power cable ports - Fan - C14 connector Parts of a Power Supply Wire bundle - Power cable ports - Fan - C14 connector

Power Supply Cables 24-Pin ATX Connector provides power to the motherboard 4 + 4 CPU Power. Older CPUs use 4, newer use all 8 6 + 2 PCIe cable for video cards. Some video cards use 6, more powerful cards use 8 4-pin peripheral power is for legacy components, 15 pin SATA cables power more modern SATA devices

ATX Power Plug Provides 3.3 Volt, 5 Volt and 12 Volt rails to the motherboard Provides a power good signal to let the mother board know that the self tests came out good Provides 5 Volt standby current Accepts a power on signal from the operating system or remotely over a network

Power Supply Troubleshooting: Symptoms Computer not turning on Computer turning off Computer restarting Components not functioning properly

Testing a Power Supply to Verify if it works Unplug the power supply from the wall Bridge the green “power supply on” cable to a black ground cable Being careful not to touch the metal bridging the ports, plug in the power supply We can then use a multimeter to test the power supply’s outlet You can also use a power supply tester in order to see if it is working. While this is a specialty device, it is not expensive: under $30

Field Swapping a Bad Power Supply If a power supply is not providing the correct voltage it must be replaced Disconnect the power supply from the wall and turn it off Disconnect the power supply from the motherboard and all peripherals Use screwdriver to disconnect power supply from case Use screwdriver to mount new power supply to case Reconnect power supply cable to components. Any cables that must be placed a certain way are keyed to not go in backwards, though legacy systems may not be this way Use wire ties and electrical tape to secure cables. This is done to have better airflow and to prevent loose cables from damaging components like fans