Canon F1-N Brochure & Specs page 45

19 SHUTTER-PRIORITY AE
After removing the power winder or motor drive, do not forget to remove the
lens' aperture ring from the "A" mark or the shutter will not release when
you press the shutter button.
Before attaching the finder or motor drive, wipe the contacts with a clean,
dry cloth to prevent poor contact from dirt.
40