Before installing the mirror box, the shutter should be wound and the mirror released into the taking position (up against the focusing screen).

After mounting the mirror box, make sure all necessary wires are available through the bottom of the camera for soldering.

Check for proper coupling of the self timer and the shutter button release.

Check that the closing curtain latch sits forward of the mirror return latch.

Check that the FP switch lever holds the magnet lever.

Select one of the mechanical shutter speeds and test the function of the mirror and shutter. The camera should be capable of a complete exposure cycle at this point.