Check the fuse in the power lead. If it is blown, then try replacing it. Model 148 takes a 3 amp fuse, and all other models take a 2 amp fuse.
If the radio still does not turn on, then bring the radio to the battery and temporarily touch the power leads directly to the battery. If the radio turns on, then you know that the radio is good and you need to double-check your wiring. If the radio still does not turn on, then the radio will require servicing.