How to Activate a Comcast Cable Box

When you receive a cable TV set-top box from Comcast, it will need to be activated before you can receive channels on it. You can activate your cable box online or by calling Comcast. Newer X1 cable boxes can be activated directly from your TV. Comcast will not activate cable boxes purchased used.

Installing the New Cable Box

Connect the “Cable In/RF In” connection to the cable wall outlet.

Use a coaxial cable to make this connection, ensure that there is a little slack in the cable so that there is no tension on the connectors.

Connect the “HDMI to TV” port on the cable box to the HDMI port on your TV.

You can use the HDMI cable that came with the box, or any other HDMI cable. Make note of the HDMI port that you use on your TV so that you can easily switch to it later.

  • Many Comcast cable boxes have multiple HDMI ports. Make sure you’re using the HDMI Out port on the box and not the HDMI Input ports.
  • If you don’t have an HDMI port on your TV, you can use a coax cable to connect the “To TV/RF Out” port to your TV’s coax port. This will not result in high definition image.

Connect the power adapter to the wall outlet.

Plug it in to the Power connector on the back of the box.

Switch your TV to the correct input.

If you connected the box to an HDMI port on your TV, switch to the HDMI input that matches that port. If you connected the box using coax cable, switch to channel 3 or 4.

Connect any additional digital adapters.

If you have multiple TVs and have active coax outlets, you can use digital adapters to connect your cable to additional TVs. Each adapter will need its own coax wall outlet.

  • Connecting a digital adapter is pretty much the same as a regular cable box. Use a coax cable to attach it to the wall outlet, and HDMI or coax cable to connect the adapter to the TV, and then connect the power adapter.
  • Make sure all of your digital adapters are connected and powered on before starting the activation process.

Activating the Cable Box

Turn on the cable box.

If you cable box has a Power button, press it to turn it on. Some cable boxes will take up to 20 minutes to warm up for the first time.

Activate on the Comcast website.

The quickest way to activate your box is to visit the Comcast Activation site:

  • Visit
  • Enter your account number and phone number.
  • Wait while your cable box is activated. This may take 20 minutes or so to complete.

Activate by calling Comcast.

If the online activation service isn’t working, you can activate over the phone:

  • Have your account number and cable box serial number handy. If you have digital adapters, have the serial numbers for those ready as well.
  • Call 1-855-OK-BEGIN (1-855-652-3446).
  • Enter the requested numbers when prompted, including the telephone number associated with the account.
  • Wait for your cable box to activate. This may take up to 20 minutes.

Activate using the on-screen menu (X1 only in select markets).

If you’re using a newer X1 box and you are in a market that supports it, you may be able to activate using the on-screen menu:

  • Make sure the TV is set to the X1’s input. You should see the X1 startup screen.
  • Select your language and wait while the X1 starts up. The initial startup time may take a while to complete, and the X1 may have to download updates.
  • Enter the information required to verify your account. This may be your whole phone number, the last four digits, or the account number.
  • Select a name for your X1 box and then wait while it activates. This may take another 20 minutes or so to complete.


Avoid purchasing used cable boxes.

All Comcast cable boxes are property of Comcast, and none are authorized for sale by other people. If you purchased a cable box from eBay, Craigslist, or any other re-seller, Comcast will not activate it because it is actually an un-returned rental. You should only get cable boxes directly from Comcast for new service, replacements, or additions.

  • Don’t believe any listing or review claiming to have Comcast TV cable boxes for sale. They will not activate, and are most likely stolen.

Check your connections.

A weak connection to your wall coax outlet or to the box itself could be causing your activation issues. Make sure the coax cable is tightened snugly at both ends.

Schedule a service visit.

Sometimes bad or old wiring may be causing a failure to activate or receive signal. Old equipment like amplifiers, boosters, and splitters from previous installations may also be causing the problem. If this is the case, you’ll need a Comcast technician to come inspect and fix the lines.

  • If the problem is with your Comcast equipment or the lines leading to your house or apartment, you likely won’t need to pay. If the problem is with the wiring in your home, you may need to pay to have it rewired.

Activate your new equipment quickly.

Comcast recommends activating equipment within seven days of the date of the order. Waiting too long may cause the order processing system to interfere with the activation.

Contact Comcast if you receive error code RDK-03007.

This error code is related to your account billing, and you’ll need to contact Comcast to verify your billing information and payment status.


  • Comcast will not activate used cable TV boxes. All cable boxes are property of Comcast, and all used cable boxes available for sale are unauthorized. You should only receive cable TV boxes directly from Comcast.

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