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. Since the insides of power supplies contain lethal AC voltages tinkering around in a PSU should be done with extreme caution.

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.

Faulty PSU symptoms
PSU faultiness can exhibit a wide range of symptoms, below is a list:

{| class="wikitable" !No. !Issue !Information
 * 1.
 * PC will not power on
 * The computer does not power on or powers on briefly with fans spinning. Other components failing can also cause this issue.
 * The computer does not power on or powers on briefly with fans spinning. Other components failing can also cause this issue.

Causes
This symptom most likely means the PSUs overload protection has kicked in and shut it off to prevent damage or catastrophic failure.
 * PSU wattage is insufficient for the installed components. To troubleshoot this refer to troubleshooting step No. 3 and 4 (To be added).
 * The PSU has failed and needs replacing or board-level repair.
 * Another component may have failed.
 * 2.
 * Sudden power-off
 * The computer will suddenly power off. This can happen at any moment but most commonly it happens when the PSU is under load.
 * The computer will suddenly power off. This can happen at any moment but most commonly it happens when the PSU is under load.
 * 3.
 * Blue screen of death
 * 4.
 * Component failure
 * }
 * 4.
 * Component failure
 * }
 * }

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