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Computer Cases

Last updated: 5/2/07

Q.  Is there a standard for chassis wiring in cases?

A.  Disk Drive Power Connectors
Yellow +12 volts
Black (both wires) Ground
Red +5 volts

The color of front panel wires can be most anything, although some combinations are more popular among chassis manufactures than others (the plugs are usually labeled on recent, quality chasses). Likewise, there is some, not total commonality among the kinds of plugs used for the various wires; e.g., the speaker connector is almost always a four wire connector with the two speaker wires connected to the two outer positions (and they are usually red and black). Generally, if they are not labeled and you don’t have a diagram, you must physically trace the wires to see what switch, LED, etc. they are connected to and plug in the LEDs to determine which way they light. Plugging them in backwards will not hurt them. Plugging a switch into an LED header and closing the switch can damage the motherboard.

See also: Determining Motherboard Front Panel Connectors

Motherboard power connectors generally conform to the drive power colors, but the best (and safest way) way to know which wire is which is to use the motherboard connector pin-out. -5 volts is usually, but not always white. With respect to Baby AT power supplies, the old saying, “Black in the middle you’re OK, red you dead,” applies to how the two motherboard connectors plug into the motherboard. The ATX power supply connector can only be plugged-in one way (or, at least that has been the case for all of the ATX power supplies and motherboards I’ve seen). The ATX specification suggests a color code, but states that no specific color code is required. Again, using the pin-out is the safest approach. Upgrading and Repairing PCs by Scott Mueller is good reference (I recommend it for all computer repair shops) and has the pin-outs for many types of power supplies. In summary, there is no color code standard.

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