I have a GP7000F. Worked wel. I replaced the starting battery and when I hooked it back up the GP7000 would turn on, go through the start up screens and then shut off. I tried to push power/clear, the diagnostic screen would come up but the buttons or knob would not work. Checked the fuse, power and ground connections. All is good, but now the unit will not turn on at all. None of the buttons seem to work and no tones on the buttons. Any ideas?