Hi,
I think it should work similar to the L1200. In the attached image, there are two knobs, A & B. Knob A is used to engage or disengage the break by rotating it about half a turn. When the break is disengaged you can move the head with the hand (If I remember correctly you turn knob A counterclockwise for that). When you engage the break, then you should move the head turning knob B
If this doesn't work this way maybe there is something wrong with the mechanism of knob A.
Francisco