No volume Re Samsung 1080i rear projection tv.   There is no volume on all but 1 tv channel but the sound also works perfectly on the dvd. Was changing channels with the tv remote accidentally (only had the tv 2 weeks) and then realised and changed to STB remote with the result no sound on other channels

Normally when you have only one channel with audio the cause is usually SAP is turned on, either on the television or the cable or Sat elite box.
If you were pushing buttons on the remote, I would suggest that the SAP button is on the remote.
On a Samsung remote, the MTS button identifies this function. It may be labeled stereo.
Make sure the remote is in the TV mode to change or check on the TV.
It may also be a button on the remote for the Cable or Sat elite box. If not then you may have to search in the menu's of the Television or the boxes.
If the set is only two weeks old (the actual set, not how long you have owned it) then it probably has an ATSC turner labeled Air that will receive local HD by using rabbit ears. If the set is over 3 years old, it will not have this feature.
It's difficult to give a full de script explanation of a solution without knowing the model or configuration of the input signal.
If this does not help, respond to this post and I will reply.