John Deere 310SG Parking Brake Problems

I have a John Deere 310SG backhoe S/N TO310SG898444 with gear shift on the floor. The braking brake won't release, checked the transmission fluid level and it is ok. It seems to be an electrical issue; I have checked all the fuses, and they are all ok. I have 12 volts to the parking brake switch to one terminal, I have 9 volts at the parking brake pressure switch, I have no power to the parking brake solenoid. Where does the solenoid get its power from? Any help would be appreciated.