car radio code?

Hi just bought a 306 meridian the last owner has put a new battery on the car and it was asking for the code but he must not know what he was doing because he pressed too many buttons and it now reads ----
tried holding wavey button for 5 secs but the screen went blank so I disconected the battery to see if that helped but now the radio wont switch on is the radio knackerd or do I have to wait for an hour like someone has suggested please help !!!!!!!!!!!!!!!!!!!