I recently installed (Tracker Marine) a 597 ci hd di. First time out everything worked fine. Second time out everything seemed to work except down imaging...I get only a dark screen with the depth lines on it. called Humminbird customer service who sent me a new transducer that I could hook up and hold over the side of the boat to see if anything comes up on the DI view but got the same dark screen. As I mentioned, everything but DI seems to work...GPS and regular sonar, depth numbers seem fine. Any suggestions before sending the head unit back to Humminbird. I did do a system reset to default settings with no result. Thought maybe Greg or some user on the forum had a suggestion. Thanks. Charlie R