there is no power goin to my audio system?

i took out the old ford cassette player from my v reg. mondeo TD because it wasnt workin when i bot the car and put my own cd player into the car and there is still no power to the audio system! i dont no if its jst a fuse but there is no manual in ma car so were would i find the fuse to check? or cud it be something else? PLEASE HELP!!!