B7610 3 point hitch question

[coho]

Question on a new to me B7610. The three point hitch lowers rapidly. The manual states that the lowering speed can be adjusted with the knob centrally located on the operators platform by my feet. Well, it seems to be frozen and will not turn either way. The manual shows the knob with a half moon arrow where the "A" end is labeled "fast" and the "B" end is labeled slow to indicate the direction of rotation to adjust the lowering speed depending on intent. There is a dot, "C" to the right on the diagram labeled "lock". No indication of how to lock/unlock the knob. Is there a lock that I am not seeing on the tractor or does anyone have any suggestions on freeing up this mechanism without damage, if it is in fact frozen? Thanks.

 

[KennyV]

Put a lot of PB Blaster on the threads... Works just like a water valve...When you screw it all the way in clockwise, it will shut off the flow of oil out of the cylinder and that will "Lock" the 3 point in the raised position because the oil will not be able to run out of the cylinder.... any partially closed position will slow the oil flow... KennyV