Check, Make sure the cables are connected. Try cleaning the laser and the DVD. Make sure the TV is on the correct input.
try swapping one of the sound cables to see if the yellow cables is in fact damaged.
1) Plug the DVD player in to the TV that it does work on. Make sure there is no disc in the player. Check the DVD players set up menu. Look in the Picture menu and change the output to "RGB" Move the player back to the TV/VHS Combi. Select the input that gives you RGB1.
2) Same as above, but this time change the Picture menu to PAL (or composite or Video....whatever is the other option name that isn't
RGB or S-Video). Retest on the Combi, but this time you want AV1.
If these don't work then you might need to have a look in the TV manual about connecting external sources. It could be that because the combi has a recorder that it's trying to stop you from copying DVD to VHS. See if there's an input on the combi that bypases the recorder.
Read more: https://www.diynot.com/diy/threads/dvd-problem-sound-but-no-picture.211588/#ixzz5FYrJiX6o
I found all this on the internet so not sure if it will help you out.
or try this link.
dvd player has sound but no picture Google Search