How can I check the fuse for radio in my Nissan SE 54?

Since changing the battery due to it drained, I put the radio code in and it worked ok. Then the CD unit kept coming up with CD error which blocked the radio out then it came back on again. Kept happening everytime I switched radio on, now the radio.CD unit is dead and I wonder if it's fused the battery. Can anyone help with explanation please? Many thanks.