bernina minimatic 807, fix it?

my bernina is old but doing really well. right now the hand wheel is tight and sticks while i sew, or try to manually hand wheel the machine. do i just need to oil it? is there something else? i have blown all the dust/material dust out with compressed air and can't find anything obstructing...when the bobbin attachment is in, it seems to be tight, when it's out, it's not tight. any ideas?

october 2008