1) Are you sure it's already modded to send a signal without USB? I'm also assuming that no red light comes on in the optical slot when you feed the ua5 a signal regardless of whether the optical cable is in or not.
2) If it was modded and your willing to crack the case open, it should be readily apparent if the board or connectors were chewed on. I refitted my optical connector into it's socket slot on a Sony MD player because the analog outs were crushed during shipping and were right next door.