radio codes

hello. I recently was given a 92 XJ6 with a myriad of problems. I'm the mechanic of the family, so i set to work andhave repaired everything on the vehicle and painted it, but the radio was dead at the time of aquisition. I replaced several faulty capactitors and the radio display sprang to life asking for 'code'. This is the radio the car came with, so i'm not some 'crack' dealer that took it in as trade for evil white powder. Is there a reasonably quick way to determine the code to energize this easily? I don't know if the speakers work, or if the antenna runs or not. Any help would be appreciated.