Well, I've gone and done it. I bought a Yashica D and thought i'd be clever and test the shutter speeds with my trusty shutter speed tester, so I set the shutter speed, opened the back, cocked the shutter and tried to fire. Nope. Worked fine before. So, I closed the back and shutter still won't fire. I guess it did not like being fired with the back open. Is it completely knackered or can it be repaired do you think? I would imagine it's going to be a similar problem to changing the shutter speed after cocking the shutter? Thank you for any assistance you can give!