To add a reverb tank to the RM50, assuming it never had reverb, you need to either get a stand alone reverb unit or, get the complete reverb pan and pc board assy from Randall. It will also have to be powered from either a 12V supply or, your chassis may already have the jack for the power tap. If no supply on the chassis, a 12V Wall wart @ 500ma or so will do. Or, call Randall customer service.