Sharing knowledge: Mamiya M645 back interlock

I wanted to share my new found knowledge concerning Mamiya M645 back and it's dark-slide interlock system. I have a back which this interlock to prevent shutter release when dark-slide is present doesn't always work. Strangely enough, if I push the blue dark-slide handle UP, it works. So I took it apart.

To take this apart, unscrew all black screws. Be aware there is one on left side, right above a pin is different. This one is 3 times longer than all the rest. (which are all the same)

Now, once I opened it, finding the reason for this fault was easy. There is a tiny switch right below where 4 pin gold connectors are. This switch is actuated by a small cam which in turn, is actuated by the dark-slide. The switch is mounted on a small printed circuit board with two very small screws. Unscrew these and the assembly comes out. Normally, when the slide is in, switch makes contact. One of the arm had a solder joint come lose (cold solder), so it didn't always make connections.

The switch contacts are connected to the two left most pins. There are three wires connected to the two right pins and one that is shared with the dark-slide switch. In other words, the second from left pin is shared. These wire look to be connected to the ISO dial.

I hope this information is useful to somebody.

Thanks for the information, I believe this may be what is wrong with one of my backs. Its very frustrating and intermittent, but I suspected the darkslide since the numbers in the viewfinder still flash even though the darkslide is removed. Once I finish this roll hopefully I can repair.

I had a Mamiya M645 and I don't remember any dark slide or film backs. Mine used film inserts that were not interchangeable mid-roll.

adelorenzo said:

I had a Mamiya M645 and I don't remember any dark slide or film backs. Mine used film inserts that were not interchangeable mid-roll.

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+1 Wrong camera, the m645 does not have a back that uses a dark slide. It does not have a back. The camera body takes inserts.

I think you guys arent quite up to date on the later mamiya 645 models. The super, pro and pro tl models are modular cameras with interchangeable backs.
Best regards

Oh, we're up to date.

http://camerapedia.wikia.com/wiki/Mamiya_M645

The thread is about the Mamiya m645, not the later models.

Soeren said:

I think you guys arent quite up to date on the later mamiya 645 models. The super, pro and pro tl models are modular cameras with interchangeable backs.
Best regards

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The OP didn't mention any of those models.

I understand the confusion here.

M645 actually refers to a particular model or models in the Mamiya line - however - I see lots of examples of people using that designation erroneously to refer to the entire line of Mamiya 6x4.5 cameras.

Way back in 2010, the OP did just that.