Dead Hummingbird 757c GPS

[Jrchip1]

Have had this Depth Finder/GPS for 5 yrs. Cost around $400-$450 new I think. A while ago it got to where I could not turn it off unless I disconnected it from the Battery (Cold boot). Then it got to where it would lock up and freeze with updating until "Cold Boot". Now I can't turn it on. I brought it with me on a family trip to either fix it, or buy a new one. I have a 12V Power supply and will start with that. Then I'll move to the on/off power switch. In a way, I'm thinking it's a nutted up processor. Any folks out there who have been down this road before? Once I take a screw driver to the case, it's all on me I know, but generally I can "MacGyver"(partially fix)stuff like this ....sometimes.