My name is ***** ***** I am here to assist you. Although the Sony unit appears as a 4 deck system, if you look at the back you will quickly find that it is all in one unit. In other words the units are not separated for repair. Th e entire unit would have to sent off to be repaired or taken in to a local repair shop. Unfortunately due to the age of this unit and the market it was intended Sony does not maintain repair parts for this unit. I did check the Sony archives to no avail. The best suggestion I have for you is to be happy you got your money's worth out of it and just chalk it up to the fact that its time to look for a new system.