Weight machines come in a variety of sizes and shapes, some intended for use in the home, others designed for the gym. However, most models share certain basic design characteristics, such as a weight stack connected to a handle or pull bar through a series of pulleys and cables. These cables are often kept at a high tension level and may wear out with regular use. Attempting to use a worn cable on a weight machine is dangerous, and you should install a replacement cable as soon as possible.
Stand by the weight stack, which is located at the rear of the machine. Remove the pin from the weight tube. Check the end of the cable for a tensioner; loosen the tensioner to add some slack to the cable. Use an open-end wrench and pliers to loosen the nut or casing securing the end of the cable to the weight tube. Remove the end of the cable from the weight tube.
Trace the cable upward until you come to a pulley. Note how the cable is looped over the pulley, then lift the cable free. Continue working along the cable's path until you have lifted the cable free of all the pulleys.
Use the open-end wrench and pliers to disconnect the cable from its anchor point; if the cable was attached to a handle or bar, place the accessory on the ground. Remove the cable and set it aside.
Fit one end of the replacement cable into the connector end of the anchor point. Use the open-end wrench and pliers to secure the cable to the anchor point. Loop the length of cable through the pulleys, following the same path the old cable used.
Insert the remaining end of the cable into the weight tube. Use the open-end wrench and pliers to secure the cable to the weight tube. Insert the previously removed pin back into the weight tube. Turn the cable's tensioner to remove any slack.
While you are removing the cable, you may wish to take the opportunity to clean any dirt or grime that has accumulated on the pulleys; use water and a mild detergent. If the pulleys squeak or stick when you pull on the cables, apply a small amount of machine lubricant.
Inspect the cable regularly for any signs of wear or fraying; it is better to replace a worn cable than wait for it to break during a workout. Check that you have properly tightened all of the cable's connection points and that the cable is completely seated in the pulleys prior to attempting to use the machine.