Mamiya C330 Professional F - panel blocking film exposure

MrBiswas · Sunday at 1:24 PM

I've put several rolls through my Mamiya C330 Pro F and this latest one had a black trapezoidal blockage at the top of every frame. It appears that the flap that flips up to block the film when the UNLOCK switch is engaged while changing lenses no longer retracts all the way back and now blocks a portion of the frame. See picture and example frame. I've had the camera for about a year and haven't had any issues otherwise.

Has anyone else experienced this issue? And are there any reliable fixes for it? I can't tell what changed to prevent the panel from getting held down and out of the way of the film.

Thanks very much.

MattKing · Sunday at 1:37 PM

Remove and remount the lens, making sure that the UNLOCK dial returns fully to the correct position.
Check to make sure there isn't something tangled up with the flap mechanism.
@Mamiya_Repair , @grahamp and some of the other members here with extensive Mamiya TLR experience may have more suggestions.
Sadly, Horst Wenzel passed away recently, so I can't recommend him for a local repair.

MattKing · Sunday at 1:39 PM

Oh, and welcome to Photrio, from either a near neighbour - assuming your location is Vancouver, BC - or a not incredibly distant neighbour - if your location is Vancouver WA.

MrBiswas · Sunday at 8:22 PM

MattKing said:
Remove and remount the lens, making sure that the UNLOCK dial returns fully to the correct position.
Check to make sure there isn't something tangled up with the flap mechanism.
@Mamiya_Repair , @grahamp and some of the other members here with extensive Mamiya TLR experience may have more suggestions.
Sadly, Horst Wenzel passed away recently, so I can't recommend him for a local repair.

Thanks for the tips. I was switching the lenses throughout this roll before I knew anything was wrong, and every frame has the same blockage. And no matter what order I use the locking and unlocking mechanism, with adjustments to other things in between, I can't get the flap to tilt all the way back down. And I by looking at it, I can't understand what on the metal piece that attaches to the flap would have kept it down and clear of the film backing. I'm wondering if some piece fell out.

And thank you for the welcome! I am in Vancouver, BC.

MattKing · Sunday at 8:55 PM

This may help.
Mine is a C330 Professional - not the later C330 Professional F though.
Flap open.

Then after a distinct "clack", flap closed:

MrBiswas · Monday at 12:52 AM

Thanks for the pictures. It appears that when I switch to UNLOCK it looks the same as yours. When it's in LOCK the panel has some spring with the metal part that attaches it to the turning mechanism. I don't understand how it would have turned further to tilt downward in LOCK.

MattKing · Monday at 9:43 AM

When in LOCK, the flap should be all the way DOWN - something is stopping that from happening.

grahamp · Monday at 12:10 PM

This is the first time I have heard of this fault, so I'm guessing a bit. I will have to pull out my cameras and investigate a bit.

Do you always wind in the bellows completely before changing lenses? There is a small projection that protrudes from the body with 'unlock' that operates the retaining wire clamp. If that is not projecting properly it may indicate a problem with the internal mechanism.

In 'unlock' the flap should be closing the film gate, and on 'lock' it drops to the base of the camera. I took a look at my C220 and C330, and the flap is connected to the pivot rod by three small screws holding a springy plate that holds the baffle. The rod has a flat ground into it. Are all three screws in place? The baffle should be in contact/close to that rod.

Operating the 'lock/unlock' control involves a little force initially, then it should release as the baffle moves to the new position.

There are some pictures of the baffle in the 220 pictures from my Mamiya TLR pages. If the baffle and mounting are in the right place, I wonder if it is the internal spring on the control that is at fault.

MrBiswas · Monday at 12:33 PM

Thanks for responding. Yes, I always retract the bellows before changing lenses and the projection that prevents opening the wire clamp is working as it should.

The three screws are in place on the pivot rod.

And the movement of the lock/unlock control is the same as you describe it.

It seems likely that an internal mechanism that forces the baffle to overrotate isn't working because I can't see what else would push it beyond the 90 degree turn that the pivot rod makes. But I also don't see how the baffle or springy plate would connect to anything internally.

Perhaps if no one else has any ideas I'll unscrew the plate from the pivot rod and see if there is something missing behind it that would force the springy plate to push the baffle past the 90 degree turn when it is switched to lock.

Sirius Glass · Monday at 7:46 PM

Welcome to Photrio!

You need to lock in place and secure the door [flap] that swings into place when one changes lenses. The door prevents film from being exposed during lens changing.

Kino · Monday at 9:18 PM

MrBiswas said:
Perhaps if no one else has any ideas I'll unscrew the plate from the pivot rod and see if there is something missing behind it that would force the springy plate to push the baffle past the 90 degree turn when it is switched to lock.

It would seem to me the plate is not being pushed down enough, rather than beyond it's intended stop; or am I misreading this?

I am unfamiliar with how the horizontal rod is secured to the baffle, but if screws hold position by tightening to a flat on the shaft, perhaps the shaft has slipped slightly. This would make sense; even if the lever/knob shows to be in the correct position, slipping out of place would index the baffle incorrectly.

MrBiswas · Monday at 10:23 PM

Kino said:
It would seem to me the plate is not being pushed down enough, rather than beyond it's intended stop; or am I misreading this?

I am unfamiliar with how the horizontal rod is secured to the baffle, but if screws hold position by tightening to a flat on the shaft, perhaps the shaft has slipped slightly. This would make sense; even if the lever/knob shows to be in the correct position, slipping out of place would index the baffle incorrectly.

Yes, that's right. Whatever caused the baffle to rotate past 90 degrees from the UNLOCK position to the LOCK position is not working properly (from what I can tell the knob to switch the positions is a 90 degree turn). So the baffle or the springy plate to which it is attached is not getting pushed down enough.

MattKing · Monday at 10:54 PM

Can you push the baffle down manually with your finger?

MrBiswas · Monday at 11:10 PM

MattKing said:
Can you push the baffle down manually with your finger?

Yes. I can push it to the bottom of the inside of the camera and it springs back to parallel with the bottom when I let go.

UPDATE: I removed the baffle from the pivot rod and tried to gently turn the pivot rod past where it stops but couldn't get it to go any further. I suspect that something connecting the pivot rod to the UNLOCK/LOCK switch on the side slipped and it's not turning enough.

If worst comes to worst, I could remove the baffle entirely and just use the camera without switching lenses mid-roll.

grahamp · Monday at 11:48 PM

I have not been inside my cameras, but the basic mechanism should be the same for C330/C220 and probably C33/C22 models if you can find a diagram.

I suspect that the control causes a cam to rotate. The cam pushes against a spring (possibly a spring steel plate?), and that is the resistance felt changing between the positions. The spring pushes the mechanism to the limits of open or closed. I infer that the spring or cam has moved, or the spring may have broken.

Can you push the baffle to complete the motion where it sticks?

MrBiswas · Tuesday at 12:15 AM

I can push the baffle down but the pivot rod doesn't move and it springs back up when I take my finger off. And I was unable to move it after taking off the baffle and trying to twist it further.

Here is a video of the baffle in motion:

MattKing · Tuesday at 12:49 AM

Can you show us - from the front and side - how the lens and shutter is resting when mounted on the camera?
I'm wondering if they aren't seated properly, and if that is interfering with the flap.

MrBiswas · Tuesday at 1:01 AM

I'll try to make another video tomorrow, but I shot a roll before I knew there was a problem and aside from the blocked part of the negative all of the frames were sharp. The lenses appear to be sitting normally.

grahamp · Tuesday at 1:07 PM

Looking at the video, I think that the rod is not rotating fully. The baffle is on a flexible mount to the rod, and that gives you the spring on the baffle. The baffle is down in the 'lock' position, and closes off the lens in the 'unlock' position (just to be sure we don't get confused ).

I think it is the mechanism that goes from the knob to the rod that holds the baffle, inside the left side of the camera body, that is at fault. It does not seem to be moving far enough to get the baffle fully down. I can only find a C220 repair document at the moment, but the basic mechanism is probably similar. The control rotates a lever, one end of which moves in a slot of a larger lever. The far end of this larger lever (beyond the pivot point) is a toothed sector that meshes with a gear on the end of the rod that carries the baffle. So moving the control about 90 degrees forces the large lever to move, magnifying the distance moved by the short end, which in turn generates enough rotation of the rod to move the baffle.

It could be that the teeth that mesh with the gear on the rod are damaged or clogged. This is speculation, of course.

The viewfinder indicator is also tied into this mechanism.

MrBiswas · Tuesday at 1:41 PM

grahamp said:
Looking at the video, I think that the rod is not rotating fully. The baffle is on a flexible mount to the rod, and that gives you the spring on the baffle. The baffle is down in the 'lock' position, and closes off the lens in the 'unlock' position (just to be sure we don't get confused ).

I think it is the mechanism that goes from the knob to the rod that holds the baffle, inside the left side of the camera body, that is at fault. It does not seem to be moving far enough to get the baffle fully down. I can only find a C220 repair document at the moment, but the basic mechanism is probably similar. The control rotates a lever, one end of which moves in a slot of a larger lever. The far end of this larger lever (beyond the pivot point) is a toothed sector that meshes with a gear on the end of the rod that carries the baffle. So moving the control about 90 degrees forces the large lever to move, magnifying the distance moved by the short end, which in turn generates enough rotation of the rod to move the baffle.

It could be that the teeth that mesh with the gear on the rod are damaged or clogged. This is speculation, of course.

The viewfinder indicator is also tied into this mechanism.

I think your explanation is likely accurate. I found a parts diagram of the camera (screenshot of relevant page below. unfortunately you have to pay to download or suffer through an ad per page: )

But I'm guessing the spring has failed or the teeth have slipped, and aren't engaging the rod properly. Not sure if it's worth trying to disassemble or if I should just remove the baffle altogether and just stick with one lens per roll of film. The viewfinder indicator looks to be working normally.

grahamp · Tuesday at 4:50 PM

I would be a pain to lose the option to change lenses - it is one of the main points of the camera. You could put in a mask in the viewfinder (there is a recess in the base of all the hoods/finders for this) to avoid using the area masked by the baffle. Unless you are really into square format this will give you something like a 6x4.5 or 6x4. At least then you can use the camera with some confidence while deciding what to do next.

Bill Burk · Tuesday at 4:59 PM

Try this https://www.beefalobill.com/imgs /MamiyaC33.zip (take out the space)

MrBiswas · Tuesday at 10:01 PM

grahamp said:
I would be a pain to lose the option to change lenses - it is one of the main points of the camera. You could put in a mask in the viewfinder (there is a recess in the base of all the hoods/finders for this) to avoid using the area masked by the baffle. Unless you are really into square format this will give you something like a 6x4.5 or 6x4. At least then you can use the camera with some confidence while deciding what to do next.

I think I would rather stick to one lens than waste all that film between frames, but maybe on occasion I could do that. Thanks for responding and the tips!

MrBiswas · Tuesday at 10:01 PM

Bill Burk said:
Try this https://www.beefalobill.com/imgs /MamiyaC33.zip (take out the space)

Thank you! I will check i out.

250swb · Wednesday at 3:21 AM

I think something to consider is if the switch is loose or been forced/over rotated and simply needs resetting. Set the camera in 'Unlock' and pry off the thin aluminium cover (it's likely you'll damage it and was originally a replaced on a service), unscrew the switch knob and see if this allows the baffle to close, if not undo the two screws holding the dial on and undo but don't remove the connecting nut to the baffle linkage, does the baffle now close? If it does tighten it back up and reassemble.

Mamiya C330 Professional F - panel blocking film exposure

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