terrano original radio no display?

i have just bought a nissan terrano 2 with what i assume to be the original radio nissan branded RDS radio as in the user manual for car. the radio apears to work in every way described in the manual. the only problem i have is the display remains blank nothing i do or have read suggests any way to turn the display either on or off. is it a fault on the radio? i know that the battery was changed before i bought it but i can find no code. the user manual gives a model no. PN-2144u. help please