I have a Radio Shack 15-2113 [A] 3-IN-ONE REMOTE and I'm trying to program my 27" RCA TV but none of the codes work. I noticed that on the only manual I was able to find, the diagram of the remote has one less button than mine. Could this mean it's different? I don't see how if the model # on the back of the remote is 15-2113... with an 'A' in a box to the right of it.