So in short, try sending stereo from the cable/other boxes.
Have a Panasonic Plasma TV with no sound when viewing via the cable box connected by HDMI cable. Just cut out one day when viewing a program.
No problem with sound when TV is connected to the cable box by coaxial cable. Also, connected another TV via the same HDMI cable and ports and sound was okay. Same when I checked the DVD player sound was okay.
In summary. TV to cable box via HDMI = no sound (picture is great). DVD player or another TV via the same HDMI ports/cable = sound okay. TV to cable box via coaxial cable = sound okay.
Any idea what I'm missing/what's going on?
Thanks!

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