does anyone know what the problem is?

i have a Seat Leon with the original radio in, the radio comes on but there is no display and no sound but i hear the cd changer starting up when it is switched on. i have tried to put the code in but nothing happens because there is no display. I took that stereo out and tried a completely different radio and it works so it must be something wrong with the radio itself. please can some one help, i need music in my car