Yes, if you open the hoses on the front end of the boom cylinders, gonna be messy though.
Is the bad solinoid on the hydraulic control valve? If its like the newer lx565 you could just unscrew the solinoid from the control valve and the spool lock will be defeated. Lift the boom and install a boom stop or chain it up with the shop hoist as you will have no safety protection at this point.
Ken