I have a UE55TU7100KXXU 55" Smart 4K Ultra HD HDR LED TV and very pleased with it. When I originally set it up with my old DVD 5.1 home theatre system was pleased to see that the sound output worked from TV to surround sound via optical output, but also via HDMI. Not only that but I could change the volume when HDMI was set as sound output, and the surround sound would turn on and off with the TV. Perfect! This is not an eARC unit as far as I am aware.
However when the kids get to the TV somehow they are pressing some option (and I've no idea what they're doing, tried to reproduce it but not succeeded), the HDMI option disappears from Sound selection. TV Speaker appears to be selected, but the sound is still coming out of the surround system (via optical presumably). Only now i of course can't change the volume from the TV remote, nor will the surround sound turn off with the TV.
To fix this I've not found a 100% reliable method. Sometimes changing TV output to the home theatre system will cure it (i.e. i can see and select HDMI as the output. Sometimes it doesn't. Sometimes it seems to fix itself (I've pressed volume up not realising the home theatre system was still off, but that actually triggered the home theatre to power on). Sometimes I have to hard power it off and on again and even then it doesn't always work.
Clearly there's something a not working perfectly in detecting that the HDMI I have plugged in is a viable sound output but I just can't work out what i might be. Any suggestions?
Virtually all our TV is watched from the smart TV menu (very impressed, works with all the apps we need to use), so really I just want it so it reliably outputs sound to the surround sound unit and turns on and off with the TV and lets me control volume. And that no pesky kids access youtube or netflix by pressing buttons I'm not pressing as for me it always stays on HDMI as the sound out but somehow when I come back to it after a some time with the kids having used it it's no longer a selectable sound options! 🙂
Hey, this might be a bit late but for anybody having the same problem, our Samsung Series 6 43" TV had the same issue with the HT-C5500 and I fixed it by unplugging and plugging in all HDMI cables.