Quote Originally Posted by BradleyK View Post
...I did something to lock up the shutter. I was able to remove the back to have a look inside but cannot see anything amiss. That said, I cannot remount the A12, nor can I remove the 80mm. Meanwhile the shutter remains open and a large flat pin on the bottom right (looking into the body) protrudes....
It sounds like you pre-released the body.

There's a lever protruding down on the right side below and to the rear of the wind crank. If you push that up, the camera goes through all of the functions up to shutter release (shutter closed, aperture stopped down, mirror up, rear curtains open) and stops at that point.

Pressing the normal shutter release will complete the cycle and return the camera to normal operation.

- Leigh