Hi, I have an old Technics SC-HDV600. For a few months only the front 2 speakers have been connected. Yesterday, I re-connected the centre & rear speakers but there is no output from them when I play a DVD. In the setup menu, the test on all 5 speakers are shown and test OK but on the audio menu screen, only '2 Channel' is shown for output and I cant seem to change it. Can anyone help?