" I made one flub-up so far by connecting the (+) of a battery replacement pack of two 2.5V 3F caps to the (+) of the circuit boards. So my Rail King GG1 makes sounds, it lights up, but it does not obey the DCS handheld controller. I changed the polarity so the cap (-) goes to the board (+). Is my GG1 fatally damaged? "
Since nobody else has answered ( I know zip about DCS ) I would try to attach a properly charged battery or supercap and do a reset to factory defaults ( 1 horn, 5 bells ) If it doesn't work with your DCS controller you may want to try it in standard AC.
