The belt on my MAC500 compressor is dead and I need to replace it. After removing the housing it looks like I should be able to remove the "socket flathead" screw and slip the old belt off and install a new one. Only the screw does not turn no matter how much pressure I put on an Allen wrench to turn it. I have oiled it with WD40 and it will not budge. Is there a special way to remove it or another way to change the belt?