The takeup spool drive unit, as removed, was covered in brass swarf. This looked pretty damning as the part that had failed. The unit unscrews in a slightly unusual way. What looks like the screw head is attached to the female (nut) part. I used a pair of small pliers and a flat blade screw driver to take the unit apart. See the 2nd and 3rd photos for more details.



Once the unit is unscrewed into three parts, I focused my attention on the right hand part (in 3rd photo). This part broke down further into smaller component pieces. It was also covered in brass swarf.



Basically the mechanism is a metal form that holds a strong cylindrical spring, with a geared top cap and a bottom cap that engages the take up spool directly. Under normal use, turning the top will result in the bottom turning also. The spring appears to perform the function of buffering shock load in the gear train.



In my insert, the top could rotate freely and transferred very little torque to the bottom of the device (where the film spool would be). This appeared to be the problem.



The top cap is held in place when the unit is assembled. In it's current disassembled state, it just lifts off. This gives some access to the spring. As the form has been created to hold the spring, it could not slide off. However, I could remove the spring by lifting one edge of it over the lip of the form and then chasing the edge round the form. This effectively unscrewed the spring from the form. Once I had removed the spring, I could clean the swarf from all the parts.



The bottom cap is attached to the form that held the spring. The top cap is free fitting. There is a notch in the bottom cap and also in the top cap that the ends of the spring fit into so that it can transfer torque between the two. Taking a closer look at my spring, I could see that there was a right angle bend in one end of the spring to create a leg that fits into the bottom notch. There was no similar bend in the other end of the spring for the top notch. It appears that there was once a bend in the spring, but it wasn't there now.



I can only assume that the excess load caused by the film jam resulted in the spring being pulled through the notch and caused the bend to be removed in the process. The loose end of the spring then proceeded to rotate inside the housing gouging the softer brass as it went, causing all the brass swarf.



Using two small pliers, one to hold the spring and the other to hold the unbent end, I bent the spring back into what I believe to be its original shape - i.e. a right angle foot on both ends (8th photo).



I then reassembled the drive unit in the reverse of how I disassembled it.