The Wire Color Standards for Computer Power Supplies

Power supply units are critical components of your computer, contributing to the stability and reliability of your computer's performance. Most personal computers require advance technology extended PSUs. PSUs use a primary circuit to feed a transformer converting the 60Hertz alternating current from a standard power source to a higher frequency. When you choose an ATX PSU for your computer, select one that adheres to industry wire color standards and consider the printed circuit board input and output voltage capacity.



ATX Power Supply Unit Connections

The main ATX power connector requires wiring to enable the implementation of all signals and power rails. PS-ON, 5VSB and PW-OK wire connections are required for compliant power supplies. PS-ON is an active low signal feeding signals for the 3.3V, 5V, -5V, 12V and -12V wiring power rails. 5VSB is a standby power voltage wire required for power down maintenance of the power rails, and PW-OK is a wiring connection to enable the power good signal. ATX PSU wiring includes input and output feeds for voltage signals and connections for PS-ON, 5VSB and PW-OK. Component object model wires connect functional and ancillary units, sometimes optional, between your computer and the PSU.

Wiring Color Standards

Most motherboards contain four to eight pins dedicated to powering up. You can also use adapters to connect a six-pin configuration to an eight-pin connector. Some heavy weight PSUs use 20-pin connections. Wiring color standards for ATX PSUs are: +3.3V, orange; +5V, red; -5V, white; +12V, yellow; -12V, blue; PS-ON, green; +5VSB, purple and PW-OK, gray. All other ground connections are black or brown. Older model PSUs use -5V lines to connect.

Diagnosing PSU Current Connectivity

When a PSU is not working correctly, disconnect the power cords from the PSU first. Then connect the PS-ON (green) and black wires with a paper clip and hook up a voltage meter to any of the black wires to measure the connectivity. If the PSU voltage output registers correctly for the unit capacity, then contact the manufacturer for further help. If the PSU voltage output does not register correctly for the unit capacity, then the PSU may be incorrectly wired or defective.

Choose Proper Functional Capacity Limits

Carefully consider the use, function and compatibility of your computer's system features. Measure these requirements against PSU capacity limits and capabilities before you equip a computer with an ATX PSU. Types of PSUs include: light-emitting diode; high current; dual power; uninterruptible and straight direct current. In addition, some PSUs have multiple type-features.