Audio Systems: 1999 Cadillac replaced radio from another Cadillac, no sound ., blown fuses, cadillac dealer

Question
I wanted a radio with CD player, bought from salvage yard, twice. Both were unlocked by Cadillac dealer, with same results-no sound. My 1999 DeVille has casette player and steering wheel controls. After replaced units unlocked,by dealer,neither has any sound! both remote and on-radio volume displays changes, but acts just like "mute" is on....but is not! Help and thanks in advance.  

Answer
The external amp is probably shot, and I think it's under the back seat. If it's a Bose system, each speaker also has an amp/speaker relay on the back of each speaker box. Check for blown fuses in your fuse box. Make sure the power antenna wire is sending +12VDC to the car, and that the antenna is going up. Extra info may be helpful , so ;
http://www.installdr.com/InstallDocs/GM/PDF/460017.pdf