Strangley I happen to own that exact model. I presume you mean the positive terminal on the alt had somthing metal go between it and the frame, like a wrench maybe. As leonz stated have the alt tested I think the regulator maybe in in the alt. But that should not stop the tractor from starting.
Remove the wires to the alt and tape them off as to make them safe
See if the tractor will start
Check to see if there is 12 volts at the fuse strip with the key off
Check to see if there is 12 volts at the fuse strip with the key in start/ and or run.
Listen to here if the fuel solenoid drops out when the key is turned off
Check the battery with an other , easy way unwire the existing and put a know good one on the ground and with CARE use booster cables put the negative to the frame last.
Check the existing battery depending on the above results.
You may a cooked the key operated switch.
Post again I will follow.
Craig Clayton