Tension assembly adjustment

The tension assembly's job is to apply an adjustable amount of tension to the top thread. After sewing a few patches I realized it wasn't releasing the tension when I raised the presser foot.  

 

So I took it apart & here are all the pieces.  The technical names for them (from left to right) are thumb screw, spring, little cone, tension plate 1&2, screw rod thingy, Thread guide spring dealy-bob, and pin.  (If that pin looks a little like a straight pin with the pointy bit cut off, you have a sharp eye)

The thread passes between the two plates (beside my thumb) which are pressed together by the spring below them

 When the presser foot is raised it activates a pin (seen above at my fingertip) which pushes the tab on this little cone 

And pushes the spring off the plate & releasing the tension on the thread

I guess the old pin was worn or cut too short so I replaced it with a slightly longer straight pin with the pointy tip cut off. Perfect!