3.5 Installing the Motherboard
3.5.2 Attaching the LEDs, keylock, and speaker
LEDs and the status lights are useful in indicating whether components inside the computer are on or working. Once the motherboard is securely installed, connecting the LEDs is usually the next step of assembling a computer. Possible LEDs that could be installed are for power, turbo, and the hard drive. The following are some important tips when connecting them:
  • Turbo – These are now mainly legacy items (both the turbo LED and turbo switch), and many new computer cases may not include them. If a case does have one, it can be connected by simply plugging into the corresponding pins. This step may be skipped. Sometimes the Turbo LED might be connected to a different component, such as the SCSI adapter, where it serves as the SCSI drive activity light.
  • Power LED – On older systems, the power LED can be found combined with the keylock switch as one 5-pin plug. Check the labels on the motherboard for a matching connector. To connect them, just plug into the corresponding plug on the system board. Make sure that they are connected separately if the system provides separate plugs for each.
  • Hard drive activity LED – These come in either 2-pin or 4-pin plugs. Occasionally, only 2 pins of the 4-pin plug are actually providing the connectivity. Consult the manual for installation procedures.

The keylock and speaker are two other wire leads that are usually connected at the same time as the LEDs. They all make up a group of small connectors and plugs that need the same amount of attention to attach them.

  • Keylock switch – The keylock switch is common with older systems. It was mainly used to prevent non-authorized individuals from booting the computer and changing the BIOS settings. They are rare in newer systems. As mentioned previously, most AT or older systems combine the keylock switch with the power LED as one 5-pin plug. Check the motherboard manual for additional instructions to plug in the keylock switch.
  • PC speaker – Most computer cases have this in a 4-wire plug. Plug the speaker wire into the designated plug making sure that it plugs into pins 1 and 4.

Additional information about connecting LED devices as well as the keylock switch and PC speaker can be found in the manual. Because they involve very small connectors, sometimes one or two connections could be connected incorrectly. If this happens, the LED will not light up when the computer is powered up. Simply turn off the system and readjust or switch between different plugs until all of the LEDs light up. Note that LEDs are polarity sensitive, and the connector may have to be reversed if they do not light up properly. Figure shows a HP Vectra that has hard drive activity, keylock, and power LEDs.