Mamiya m645 film camera will not sinc flash

The vertical shutter sliding lever gets locked if the film doesn't get advanced to the next frame, and the mode selector is set for single exposure. You can't trip the shutter unless you have film in the camera and you forward the film to the next frame. That should allow you to release the shutter with the sliding lever.

Need servicing from the service center. They disassemble the camera & unlock the shutter from internal side.

This button you speak of is an alternate way of depressing the shutter it is also a way in which you can use a shutter release cord to take pictures. the button itself is not meant to come out of the camera. Once you load your film or 2 empty film spools (to test to see if the camera is working properly) into the camera and wind the film crank then you will be able to depress that button and fire the shutter.

http://www.butkus.org/chinon/mamiya/mamiya_c330f_prof/mamiya_c330f_prof.htm

From the manual:
"If the error display is not canceled when the shutter release button is pressed again, insert the Dark slide, half-press the shutter release button while pressing the roll film holder's manual film advance button to wind up the film, then contact your nearest Mamiya agent or service center."

If you need a manual, you can download one from
http://butkus.org/chinon/mamiya/mamiya_645af/mamiya_645af.htm

You might want to check and make sure the battery is still good. If you purchased the camera used and didn't change the battery then this might be the case.

But in the mean time this is what you need to do:
1st-make sure that the shutter speed dial is set to any shutter speed other than the red circle w/red ring. If your camera is set to that it will drain your battery when not in use since it is designed to be an automatic setting. I set mine to 1/125th to do this push in the circular dial on the side and at the same time turn the knob.

2nd- locate the 2 levers on the opposite side of the shutter speed dial. Once you found them then position the back lever all the way forward towards the setting for "MULTI" and position the lever towards the front straight up.

3rd- then wind the film crank till it won't wind anymore and depress the shutter, if it is wound and the shutter release is still stuck then skip to the fourth step, if something happened and you heard a click then still proceed to the next step because no the shutter release will be temporarily stuck.

4th-Once both of these levers are in this position there should be a red button just behind the shutter release button on the top right side of the camera.... drum roll please...."Push the red button" what you should hear is a rather loud click, this click is the mirror releasing allowing you to: 1 wind the film crank and take another picture and 2 this also now allows you to see through the lens again (assuming that you have a lens on the camera).

In Conclusion: without a battery that is fully functional in the camera this is how the camera will operate once you get a battery for your camera then reposition the levers on the side of the camera opposite of what I suggested (this will be the normal operating mode for the camera with a battery) then when you wind the film crank and depress the shutter everything will function normally.

However you can click here for support:
Support When you need it

Nice camera! Do you mean the battery housing cover plate? It should swing open like a small door when you press the cover latch.

If you are referring to the circular threaded hole on the bottom of the camera body, it is actually the attachment point for a tripod mounting plate. Mounting the camera is optional- no need to have anything screwed in here. Load film, load battery, advance film with the crank arm, and shoot away! Have fun.

Here's a link to the user manual with illustrations:
http://www.photo-manuals.com/manual/mamiya/medium-format-camera/m645-1000s/

This is not the best solution as it indicates a faulty film back. The film should advance without resorting to activating the film-wind release lever. That is only for intentionally advancing a partially exposed roll of film. Make sure the multi-exposure lever is not engaged and that the counter does advance and the red mark disappears as you advance to an unexposed frame.

This is likely because the shutter has not been cocked all the way. Return the lens to the fully locked position and advance the film with the lever all the way down to reset the shutter. If it still doesn't work, move the lever to M for multiple exposure, make sure the back is aligned and trip the shutter release. Then fully **** the shutter again by pressing the advance lever down fully and again until it is reset. Then try to remove the lens again.

I recently had a similar problem and found the answer to be the shutter release on the lens itself.

When the using the shutter release, (mirror up feature), on the lens the shutter release, screw in portion, in the lens will actually will pop out to accomidate for the cable release.

There will be a small red circle around the base of the area where the cable release would screw into.

Try pushing that back in. Worked for me.

Good luck,

James