How can I get sound from 8 yr old Grundig TV When con. to DVD Player?

I have an 8 yr old 80cm Grundig TV. It was recently connected to a Bose 123 sytem and works perfectly. I need to send the Bose away for repair (DVD stuck in tray). I connected a new DVD player (LG) to the TV using the supplied cable (red yellow and white connections). I get picture but no sound. I went a bought a differient DVD player but it has the same results. I have tried all audio settings on the TV but cant get the audio to work.