How to connect Internal System Cables, Part 1

In the course of system maintenance, it may become necessary to disconnect and reconnect internal cables. This article illustrates the internal connections for front panel IEEE-1394/firewire, HD-audio, USB, and 4-pin USB connections.

It is important to understand that orientation is "key". Most of these connectors are keyed to prevent making an improper connection and cause damage, but it still is possible to do so.

Left is an image of the front panel audio connector and its orientation to the motherboard's onboard audio front panel header. Notice the pin arrangement and how the connector matches it. The white pin block corresponds to the missing pin position on the header.

If a user has a sound card in his system, this cable would be connected to the header on the sound card instead.

Left is an image of a IEEE-1394/firewire connector on an EVGA 680i motherboard. Again, the block corresponds to the missing pin in the header.






The same is true for the USB connector (left). The block corresponds to the header's missing pin. Unfortunately, these two connectors are very similar looking and it is possible to accidentally connect a firewire connector to a USB header, or vice versa, so be careful.




This is potentially damaging for your system because the purposes of the pins are different between headers, as seen below. Most headers have colored bases or collars, but do not rely on matching up colors as this is not standardized. Some motherboards do not use the same coding schemes. For instance, the common color for a firewire header is red as in the image seen above, while the reference below is colored blue. Likewise, the USB header above is colored blue, but the reference below is black.


Left is an image of two USB headers side-by-side. The 5-pin USB connector is oriented on the even-numbered pins (refer to pin numbers above) of the USB header in the background. These connectors are often 4 pins wide (covering either pins 1-3-5-7 or 2-4-6-8) or 5 pins wide (the 5th hole covering the missing pin 9 or pin 10). Here there is no block to "key" the connector, so it is important to know the orientation before you begin. The voltages applied to these pins require that the RED wire in the connector (+5V) should correspond to pin 1 or pin 2 and the black wire (Ground) should correspond to pin 7 or pin 8. Connectors of this type are common for internal media readers, certain tuners, and other devices that operate on the USB bus.

The images above may not apply to your system and should only be used for orientation reference. Be sure to consult your motherboard manual for assistance locating the pin headers for your particular motherboard and to take proper precautions against ESD.

Continue to Part 2