I am trying to troubleshoot my 898c. About 2 yrs ago the details quality really dropped off. Picture is really blocky or pixelated. I updated it, reset factory settings but made no difference. I see the 898 is on Humminbirds will not repair list. So I'm trying to decide if the problem is in the unit or transducer. Is there a way to troubleshoot the transducer without buying a new one first. Looking for any help I can get getting the sharpness of my image back.