Mamiya C330 cocking lever impedes shutter firing

[jonmon6691]

Hi there, currently borrowing my friends project camera which came with a "needs some TLC" warning. After a few minutes playing around with it I noticed that the shutter only fires intermittently, but only after it was cocked via the body-mounted cocking mechanism. Upon closer inspection, I can see that by the time the film advance crank is locked for the next exposure, the body-mounted cocking lever hasn't fully returned to its "up" position. Its nearly almost there, but when the shutter is fired, the shutter's cocking lever snaps up and stops once it hits the body-mounted cocking lever and doesn't go far enough to actually fire the shutter. Giving the lever a little nudge then fires the shutter. This is a nightmare, especially for faster shutter speeds where its hard to tell if you heard the shutter or not.

The drive shaft for this cocking mechanism is on the other side of the camera and I can see the sprocket and rack peeking through the case and it looks to me like if the mechanism was skipped one tooth further, then the cocking lever would be able to return just a little bit further each time and allow the shutter to fire reliably.

Does anyone have experience with this issue? Is there a straightforward repair that I'm not aware of or is re-clocking that drive going to have unintended consequences? Also if there are some better repair documents out there please share! I've only been able to find the standard manual that comes in the box but it doesn't give any helpful repair diagrams.

 

[jonmon6691]

Update: So I found out how to move that gear, the pinion shaft has a circlip at the end which once removed allows the shaft to slide back towards the camera body and allows it to disengage from the rack and move freely. So I tried moving it one tooth down, but alas, one tooth of movement was too much and the arm wouldn't move far enough down to fully cock the shutter anymore. So I moved it back to its original position and reinstalled the clip. It seems like either the shutter needs a CLA so it rebounds with enough force (or less drag) so that it can push that body lever out of the way the roughly 1mm required. And/or the mechanism in the crank system also needs to drag reduction.

I assume spritzing a little tri-flow lube is frowned upon in the world of vintage cameras.... I'm tempted but knowing the shutter has a calibrated escapement, that seems like a pretty bad idea, at least for that area specifically.

 

[jonmon6691]

Oh also, I was able to find some mechanical diagrams for the Mamiya C330, posting here in case someone is searching for them someday down the road

 

[reddesert]

The shutter should not have to push the body cocking lever out of the way. There may be a little room for the cocking lever to move up, but the shutter should not have to push it. It sounds like the shutter is fine and it's the mechanical interface that is the problem.

Never squirt Tri-flow into a shutter. It's much too oily and will gum it up. This is a working shutter so don't squirt anything into it. (I will admit to freeing a sticky shutter by using electronic contact cleaner that evaporates without residue, but absolutely not Tri-flow.)

Someone who really knows like user Mamiya_Repair will probably be along to suggest the proper solution, but the two places I would look are:
- The body cocking lever or lens cocking handle might be a little bent, or reshaping it a tiny amount may relieve the problem.
- The lens/shutter is mounted with a locating pin on the back, but there is a tiny bit of rotational slop. If you loosen the retaining ring on the back (and the brace between the lenses if there is one), you may be able to rotate the lens just enough to clear the cocking lever.

 

[jonmon6691]

The shutter should not have to push the body cocking lever out of the way. There may be a little room for the cocking lever to move up, but the shutter should not have to push it. It sounds like the shutter is fine and it's the mechanical interface that is the problem.

Never squirt Tri-flow into a shutter. It's much too oily and will gum it up. This is a working shutter so don't squirt anything into it. (I will admit to freeing a sticky shutter by using electronic contact cleaner that evaporates without residue, but absolutely not Tri-flow.)

Someone who really knows like user Mamiya_Repair will probably be along to suggest the proper solution, but the two places I would look are:
- The body cocking lever or lens cocking handle might be a little bent, or reshaping it a tiny amount may relieve the problem.
- The lens/shutter is mounted with a locating pin on the back, but there is a tiny bit of rotational slop. If you loosen the retaining ring on the back (and the brace between the lenses if there is one), you may be able to rotate the lens just enough to clear the cocking lever.

Thanks Red, I appreciate the help. I have some contact cleaner but I hear what you're saying that there shouldn't be any interference at all so its not a matter of the shutter needing a clean out. For what its worth, I can nudge the cocking lever up after cranking the film advance and then the shutter fires reliably. Pretty annoying but means the camera is usable.

I had the same thoughts as you suggested, maybe a small twist along the double-90 section may give the margin it needs. I'm very hesitant to resort to filing the edge since the part is plated, and its also not my camera... As for the slop in the mounting of the lens, there definitley is some wiggle room and I've played with that quite a bit but it seems to settle back into a certain position after a few shots and goes back to not firing.

Thanks again for the input, I'll report back if I find a good way to twist that part safely. I've got a roll to shoot through until then to check the shutter is working and the focus is accurate

 

[Tel]

Cut to the chase: contact Bill Rogers (mamiyarepair.com) who posts regularly here. A very helpful and knowledgeable guy.

 

[MattKing]

I think the lens plate is mounted too high on the camera, which means the lenses and shutter are too high.

 

[jwd722]

Ok, so I don't know what the problem is but I can tell you this much. I have a C33 and the pictures show that even with a toothpick between the shutter lever and the shutter stop it still fires the shutter.
The shutter stop has about 3mm of freeplay as also shown. My only "guess" is that the shutter stop does not have this freeplay.(?)
Looking at the pictures I guess it's time to clean my camera!