I recently assembled a Mamiya 645 Super by buying a body, a film back and an AE Prism finder, all separately, on Ebay. I have now assembled it in accordance with the manual, but cannot get the shutter to fire, even in the 1/60th manual mode. The Multi button is not activated, or the Shutter Lock button. Is it because I havent got a winder on the body? There is a winder on the film back, so I assumed this would have the same effect, but I suspect now that it doesnt. Also, is there a separate manual for the AE Prism finder?