No one publishes service manuals for anything anymore, claiming it is all proprietary.
However, the bigger issue is that current modern gear is unfixable. That is because the components are surface mounted by robot, using hot air soldering. Basically the rule these days is that if it fails out of warranty you chuck it.
I tried to fix a sound bar for a friend, and I think I could have repaired it may be. The part I needed was nowhere in the US. A site in China said they had it. Of course they lied, and what they sent was the wrong component. So off to the recycling center with that one.
Anyhow, what is the exact problem with your soundbar?