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Cables and Connectors

Internal cables commonly connect from a device to the motherboard, the power supply to a device, the motherboard to the front panel buttons or ports, and/or from a card that occupies an expansion space to the motherboard. Cables can be tricky. Inserting a cable backward into a device or adapter can damage the device, motherboard, or adapter. Most cables are keyed so the cable inserts into the connector only one way. However, some cables or connectors are not keyed.

Removing a cable for the first time requires some muscle. Many cables have a pull tab or plastic piece used to remove the cable from the connector and/or device. Use this if possible and do not yank on the cable. Some cables have connectors with locking tabs. Release the locking tab before disconnecting the cable; otherwise, damage can be done to the cable and/or connector.

Be careful with hard drive cables. Some of the narrow drive cables, such as the one shown in Figure 4.3, are not as sturdy and do not connect as firmly as some of the other computer cables. Also, with this particular cable type, it does not matter which cable end attaches to the device. A 90°-angled cable (see Figure 4.4) may attach to devices in a case that has a limited-space design and may have a release latch.

Figure 4.3

Figure 4.3. Both cable ends are the same

Figure 4.4

Figure 4.4. 90°-angled cable with a latch

Each cable has a certain number of pins, and all cables have a pin 1. Pin 1 on a cable connects to pin 1 on a connector. In the event that the pin 1 is not easily identified, both ends of the cable should be labeled with either a 1 or 2 on one side or a higher number, such as 24, 25, 49, 50, and so on, on the other end. Pins 1 and 2 are always on the same end of a cable. If you find a higher number, pin 1 is on the opposite end. Also, the cable connector usually has an arrow etched into its molding showing the pin 1 connection. Figure 4.5 shows pin 1 on a ribbon cable.

Figure 4.5

Figure 4.5. Pin 1 on a ribbon cable

Just as every cable has a pin 1, all connectors on devices, adapters, or motherboards have a pin 1. Pin 1 on a cable inserts into pin 1 on a connector. Cables are normally keyed so that they insert only one way. Some manufacturers stencil a 1 or a 2 by the connector on the motherboard or adapter; however, on a black connector, it’s difficult to see the small number. Numbers on adapters are easier to distinguish. When the number 2 is etched beside the adapter’s connector, connect the cable’s pin 1 to this side. Remember that pins 1 and 2 are always on the same side, whether on a connector or on a cable. Some technicians use a permanent marker to label a cable’s function. Figure 4.6 shows an example of a stenciled marking beside an adapter’s connector. Figure 4.6 illustrates the number 2 etched onto the adapter, but other manufacturers stencil a higher number, such as 33, 34, 39, or 40, beside the opposite end of the connector.

Figure 4.6

Figure 4.6. Pin 1 on an adapter

Motherboard connectors are usually notched so that the cable inserts only one way; however, not all cables are notched. Some motherboards have pin 1 (or the opposite pin) labeled. Always refer to the motherboard documentation for proper orientation of a cable into a motherboard connector. Figure 4.7 shows the motherboard connectors used for the thin cables shown in Figures 4.3 and 4.4. These connectors commonly have hard drives and optical drives attached. Figure 4.8 show three other motherboard connectors that are notched.

Figure 4.7

Figure 4.7. Motherboard connectors for narrow cables

Figure 4.8

Figure 4.8. Three motherboard connectors

Some manufacturers do not put any markings on the cable connector; even so, there is a way to determine which way to connect the cable. Remove the adapter, motherboard, or device from the computer. Look where the connector solders or connects to the motherboard or adapter. Turn over the adapter. Notice the silver blobs, known as solder joints, on the back of the motherboard or adapter. Solder joints connect electronic components to the motherboard or adapter. The connector’s solder joints are normally round, except for the solder joint for pin 1, which is square. Look for the square solder joint on the back of the connector. If the square solder joint is not apparent on the connector, look for other connectors or solder joints that are square. All chips and connectors mount onto a motherboard in the same direction—all pin 1s are normally oriented in the same direction. If one pin 1 is found, the other connectors orient in the same direction. Insert the cable so pin 1 matches the square solder joint of the connector. Figure 4.9 shows a square solder joint for a connector on the back of an adapter.

Figure 4.9

Figure 4.9. Pin 1 on a connector

Specific cables connect a motherboard to lights, ports, or buttons on the front panel. These include the power button, a reset button, USB ports, IEEE 1394 ports, a microphone port, a headphone port, speakers, fans, the hard drive usage light, and the power light, to name a few. Be very careful when removing and reinstalling these cables. Usually, each one of these has a connector that must attach to the appropriate motherboard pins. Be sure to check all ports and buttons once you have reconnected these cables. Refer to the motherboard documentation if your diagramming or notes are inaccurate or if you have no diagrams or notes. Figure 4.10 shows the motherboard pins and the connectors.

Figure 4.10

Figure 4.10. Motherboard front panel connectors

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