You will have to label every single tube that connects to the controller, than remove it and send it to Toro for repair. No other practical alternatives exist. The only plan of attack that gets you going soonest, is to replace all the valves and install a modern solid-state controller. Or, you leave all the existing valves in place, and buy (big bucks) a hydraulic/electric conversion assembly, as offered by Toro, and a new controller.