Question My lg 43uk6300pvb smart TV has no internal sound when connected with RCA cable to decoder

[waletext]

I bought my lg 43uk6300pvb thin Q TV few months ago , but when connected with RCA cable to decoder the internal TV sound was not working and my decoder has no hdmi port ,my TV sound set up only has hdmi arc, internal TV sound and optical , plz is any other way I can connect my TV wit my decoder to make the sound work

 

[hang-the-9]

Need details about this "decoder" and exactly what ports are connected to what on the TV. If you are talking about your cable box, contact the cable company and ask for a newer model that has HDMI.