Power Supply (PSU)

A Power Supply Unit (often shortened to PSU) is a device that converts AC power to DC power for your desktop computer. Modern PC power supplies use the ATX standard which dictates the form factor and voltages.

24 PIN Connector
The 24 PIN connector provides all necessary power to the motherboard. Older motherboards may have a 20 pin connector instead, also some PSUs may have the 24 PIN connector split into a 20+4 version for backward compatibility.

CPU Power
The CPU power connector provides power for the CPU. The connector itself is usually a 4+4 pin type connector and the motherboard may have only a 4 pin header, higher-end motherboards usually have a full 8 pin header.

PCI-E Power
The PCI-E power connector provides extra power for PCI Express expansion cards, most commonly graphics cards. It may come in 6 pin, 6+2 pin (for backward compatibility), or 8 pin versions. A single 6 pin can supply up to 75W, while the 8 pin version can supply 150W.

SATA Power
The SATA Power connector provides power for SATA-based hard drives, solid-state drives, and Hybrid drives.

MOLEX Power
The MOLEX Power was used for floppy drives, DVD drives and older peripheral cards. In modern systems, it is frequently not used.

Common troubleshooting steps
Here are some common troubleshooting steps you can do if you believe your PSU is not working or is faulty.