My suzuki 1988 gsx600f Katana is blowing fuses.?

My 1988 Suzuki GSX600F Katana with 31k miles is blowing the second from the rear 10 amp fuse. The Tachometer, turn signals, and brake lights stopped working. I have cleaned the connections under the fuel tank and the battery terminals. It runs with the tach and lights working when I hook up the jump starter to it, but immediately blows the fuse when i disconnect the jumper cables. Any guesses? Garage kept and in very good condition.