I have been trying to install a Digitrax sound decoder in DCC ready Light Mountain I just purchased.   I have double checked all the connections to make sure there are no solder bridges between the solder points on the pc board, but the decoder still is detecting a short circuit and shutting down motor control.   All the sound functions and the headlight work fine but ther is no motor control.   I checked all the connections on the pc board and the the wiring harness but can not fine the short.   Does anybody have any idea where else I should look.