1. Introduction to Computers
Power Supplies

2. 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

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

4. 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

5. 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

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

7. 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

8. 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