Originally Posted by cumbaya19
I have the cheapest cable box comcast has to offer. It only has composite hook ups. My TV is the samsung ln46b650 TV. It has a built in QAM. Currently, I have the cable running into the box, and then have anoter cable from the box going into the TV + the composite cables. How do I scan for HD channels? When I do the auto, I don't get any channels
There are no "channels" with a composite (yellow video, white/red audio) connection. Composite is a "line input" not "channels."
If you connect the Comcast cable converter box RF (threaded) output to your TV and run the channel scan you'll find one "analog" channel, 3 or 4, corresponding to the "output channel" of the Comcast converter box.
If you connect the raw Comcast coax cable to your TV and run the channel scan you'll find whatever clear QAM channels are being provided by Comcast. In my area Comcast is currently providing more than one hundred clear QAM sub-channels. These clear QAM sub-channels are generally those found in the "expanded basic" tier of service.
Cable company converter boxes "map" cable "services" to "locations" according to that cable company's numbering scheme. The same services received by a clear QAM tuner-equipped device will appear on sub-channels that may have no similarity to cable company assigned "locations."
Cable company provided converter boxes or Cable Cards are required to receive "scrambled" services. Comcast's basic "digital to analog converter" is the Pace DC50X Digital Transport Adapter (DTA) that provides only an RF output and no "scrambled" services.