have done this and reset my ipod, the music still cuts out when the backing light dims? any suggestions

I have a 6th generation Ipod nano (it is already a replacement after the firsts hold button broke within its warrenty) So now my replacement before it was even a year old has stopped working, the music cuts out when the screen goes dark. I have checked the earphone socket and tried different earphones, I have reset the ipod and still nothing has changed. the music still cuts out when the screen goes dark, any suggestions?