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Author Message   Rpinchbeck Tinkerer Username: Rpinchbeck Post Number: 3 Registered: 10-2006 Rating: N/A Votes: 0 Posted on Monday, January 14, 2013 - 04:38 pm:    I'm trying to diagnose an issue I'm having with a 645 Pro. Recently put this system together so I have no confirmation that it all is functional. However, I do believe the back is faulty as when I put the back on the shutter won't fire. If I put some tape over the electrical contacts it will fire! I've investigated the four pins on the back and have determined the two pins on the right most, as you look at the back with the contacts facing you, are for the ISO dial. The left most two pins are undetermined. On the camera body, as you look at the expose back, the two right most pins power up to 3V when the shutter fire button is pressed. So, what in the back could want 3V for? Electrical interlock switch for dark slide? Something else completely? Cheers, RP