fish finder

[ignasty]

My question is pretty simple I have a koden cvs 822 fishfinder it turns on but nothing shows up on the screen the model is from 1980 I do believe. but im looking into upgrading into todays newer models .just wondering what everyone else was using? I do a lot of striper,cod,and tuna fishing..I already have a gps, radar so I'm not looking for a combined model but a seperate model just for depth, and finding fish. Any input would be greatly appreciated. THANKS..