I'm using an RCA connector, and no sound is playing. Picture is there, DVD plays but no sound. I had a separate unit of this exact same model play just fine on the exact same tv. I've checked the audio settings and nothing works, it's currently set to stereo. Thanks for your help. I think it may be an internal issue. HDMI picture and audio is not working.
If you are using the single yellow RCA jack on the DVD that is for video only. Use the white and red RCA jacks adjacent to it for audio.
On some older DVD players you have to turn on the HDMI output which will turn off the other outputs. Check the manual https://www.sony.com/electronics/support/product/dvp-nc85h/manuals
HDMI carries video+audio and will give you a much better picture.