not sure what happened. Have a 798 at console. one SI ducer and a 2d ducer epoxied in hull and connected via Y cable. Sat. both worked. Sunday alll works fine except i get no SI or DI read. just black screen and some very slight "stuff" on the left side. thought maybe the ducer was knocked but seems fine. How do I troubleshoot this? does it have to be on the water?