There are advantages to using a Comcast cable box, but you do not need one to have cable service on your TV. You can also exchange it for a new box if you're having technical difficulties. A technician usually installs your cable and cable box, but you can remove a Comcast cable box and return or exchange it by yourself.
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Unplug your Comcast cable box from the electrical outlet.
Unscrew, from the back of your cable box, the coaxial cable that comes from the wall outlet. Twist the connection counterclockwise until you can pull away the cable completely. If you want to keep a cable connection without the box to your TV, screw the end you've removed from your cable box into the jack on the back of your TV. It looks the same as the one on the cable box. Screw clockwise until tightened.
Disconnect any audio or video cables running from the cable box to your TV or audio equipment. These can include RCA jack cables with three colored plugs on the ends or an HDMI cable with one plug on each end. Remove the plugs from your TV as well as the back of the cable box. The cable box should not have any cords attached.