Bronica C Helicoid Removal

ThomasW · Jan 9, 2023

A few months ago I purchased a Bronica C which appears to be in good condition and performs well with the 3 Nikkor lenses I have for it, a 50, a 75 and a 200 mm, also all in good condition. The shutter and apperature controls and the focus are all correct. I have recently purchased a Komura Telemore 95 2x Teleconverter for this camera; I beleive that it mounts in the place of the Helicoid and then the Helicoid is, in turn mounted in it, and of course the lens is in turn mounted in the Helicoid. My problem is that the Helicoid removal button will not depress at all. so ergo I can not remove the Helicoid - I know that IF it will depress, I have to turn the Helicoid counterclockwise. The lenses themselves easy demount and remount on the Helicoid. At some point, I would like to purchase a bellows so sooner or later, the Helicoid will have to be removed. I have read everything that I can find, including the C, S2 and S2A manuals. Is there some Bronica cosmic secret of which I am unaware to remove the Helicoid? Any help that could be provided would be appreciated.

reddesert · Jan 9, 2023

No, there's no secret. (Looking at a Bronica S2, which should be the same as a C.) The button pushes a plate that is directly behind the button back by a couple of mm, moving it out of the way of the bayonet flange on the helical so that the helical can be turned to dismount. Unfortunately, this mechanism is difficult to access while the helical is mounted.

The button should stick out from the face of the camera by a couple of mm, and when I mount the helical and turn it fully clockwise, there is an audible click and the button pops out by another mm or so.

Perhaps your mechanism is slightly hung up. I would try rotating and wiggling the helical back and forth a little (dismount the lens and try holding the lens mount tube to rotate, because turning the focus ring only can tension it in one direction). You might be able to inspect the mechanism from above/behind by removing the focus screen, but I'm not sure of that and if you remove the screen you may need to re-shim it to restore correct focusing.

cramej · Jan 9, 2023

No secret - the button should depress and the helicoid unmounts (looking at the front of the camera) counter-clockwise.

ThomasW · Jan 9, 2023

reddesert said:
No, there's no secret. (Looking at a Bronica S2, which should be the same as a C.) The button pushes a plate that is directly behind the button back by a couple of mm, moving it out of the way of the bayonet flange on the helical so that the helical can be turned to dismount. Unfortunately, this mechanism is difficult to access while the helical is mounted.

The button should stick out from the face of the camera by a couple of mm, and when I mount the helical and turn it fully clockwise, there is an audible click and the button pops out by another mm or so.

Perhaps your mechanism is slightly hung up. I would try rotating and wiggling the helical back and forth a little (dismount the lens and try holding the lens mount tube to rotate, because turning the focus ring only can tension it in one direction). You might be able to inspect the mechanism from above/behind by removing the focus screen, but I'm not sure of that and if you remove the screen you may need to re-shim it to restore correct focusing.

Your suppositions that an S2 and C should be the same, at least for this purpose, and that the mechansim is slightly hung up both sound reasonable. I've tried exactly as you suggested for attempting to rotatte the helicoid back and forth with the lens removed, albeit to no avail. The button will still not depress. I'll look at removal of the focus screen tomorrow with better light and a less tired set of eyes and after some carefull reading about focus screen removal and re-installation first.

ThomasW · Jan 9, 2023

cramej said:
No secret - the button should depress and the helicoid unmounts (looking at the front of the camera) counter-clockwise.

Thank you also. Sadly, should depress isn't the case; absolutely will not depress is the situation, much less turn the Helicoid counter-clockwise. I suspect that the earler respondent's suggestion that the mechanism is slightly "hung up" is correct. The trick will be to free it.

ThomasW · Feb 9, 2023

ThomasW said:
Thank you also. Sadly, should depress isn't the case; absolutely will not depress is the situation, much less turn the Helicoid counter-clockwise. I suspect that the earler respondent's suggestion that the mechanism is slightly "hung up" is correct. The trick will be to free it.

I also just noticed that the Depth-of-Field Preview button does seem to function with the lens. I removed the lens and found that when I depressed the botton, the lever that it accuates within the camera body moved appropriately but on observing the alignment of where the matching lever on the lens would be when installed in the Helicoid, it would be rotatedd [erha[ps 20 or 30 degrees too high to be moved. Does this make anyone suspect that the Helicoid had been dissassembled and "rebuily" by someone that didn't know what they were doing, (and therefore is also jamming the Helicoid Removal otton on the camera itself)? I would appreciate any comments you or anyone else could offer.

reddesert · Feb 9, 2023

Some pictures would really help.

I assume you meant to write that the DOF preview does not function? If the lever inside the mount is not actuating the lens aperture, then the lens won't stop down when you take a photo. Note there is a lever inside the camera that moves a sliding piece on the inside of the helicoid that moves the lens lever.

When the helicoid and lens are properly mounted on the camera (on an S2, I assume the C is the same), the focus mark on the helicoid is not straight up like on most cameras, but well to the left of center as you look down at it. IIRC, if you mount the lens and look from the front of the camera (subject's POV), the red dot on the lens should be at about 12 o'clock, the focus mark on the helicoid at about 1:30, and the aperture lever at about 3 o'clock.

There are some light baffles inside the helicoid fastened by screws at the rear. If these get loose, they can jam against the lens. I think I had to tighten these once. I don't think they could jam the helicoid release button, but maybe the helicoid isn't fully twisted into place and that's why the button won't depress.

You may be able to inspect it from the back by firing the shutter on B and holding it open with a locking cable release. Care is required because if the release slips and shutter closes while you're poking anything into the camera, bad things will happen.

ThomasW · Feb 9, 2023

Thank you very much for your reply.
Your assumption that the DOF button does NOT Depress is both Correct and Incorrect. It depresses just fine, and with the lens removed I can seethe lever inside the Helicoid moves as it should. What it doesn't do is provide any DOF preview with the lens mounted, not suprising as it appears that the mating lever on the lens is positioned about 40 to 40 degrees above it and so is never operated by the DOF lever on the Helicoid.
In passing, at least the focus seems "dead on" as I could see after I processed my first film through this camera. Strangely, if the aperture isn't clsong down automatically when the shutter is depressed, the exposures were pretty good. Odd.
Good suggestion about the Photos. I have made three and attached them. As you can see, your supposition regarding the position of the Red Dot and Focus Mark were correct as the Red Dot is indeed at about 10:30, not 12:00, and the Focus Mark is at 12:00 instead of about 1:30, both as you noted they should be.
The Helicoid will not twist in either direction. I will finish the film currently in the camera in a few days and attempt to see if I can see if there are any loose screws jamming either the Helicoid or the Lens. Thank you for noting that "bad things can happen". I have a cable release with a lock which I will insure is working completely correctly before attempting your suggestion.
Of course, if you see anything in these 3 photos that gives you any ideas, I would again be appreciative of hearing them.

abruzzi · Feb 9, 2023

I don't have a C or S2 so its hard to say for certain, but as @reddesert mentioned, the focus indicator isn't top-dead-center (at least not on my EC-TL) but, if facing the front of the camera it is at about 45º clockwise from the top. But your pictures seem to show it at the top, 12 o'clock position, which would make me thing that either there is something somewhat wrong with the helicoid or it isn't fully mounted?

ThomasW · Feb 9, 2023

Abruzzi and Reddesert:
This now really makes me think that there is major problem with this Helicoid and that some previous owner had some less-than-qualified work done on either it or the camera. My understanding is the C, S2, S2A and EC-TL cameras all have the same Helicoids and use the same lenses so this all makes sense; having two people make the same observation of the lens position was a big help. I found 3 photosgrpahs within my PDF copy of the Owner's Manual that show the proper position if one looks carefully. It also occured to me that I do not need to use up the film in my C as I can simply open up the camera within a Changing Bag, (as if I was loading film to be processed into a developing tank reel), and see if what Reddesrt has suggested in true. I just hope that some clown in the past didn't Crazy Glue stuff together.
Thank you both very much.

abruzzi · Feb 9, 2023

good luck. FYI, KEH has a used helicoid if yours is hosed and you can get it off, though I don't know if shipping to Canada would make that unattractive.

ThomasW · Feb 9, 2023

Thank you for that. I'll check out KEH. There are a few other sources, even one in Canada that might be possible. The Shipping costs from the USA and many other countries is usually not unreasonable and the import tax is usually only the 13% Harmonized Sales Tax - a Value Added Tax - that we would normally pay on new goods here anyway. If you are interested, I'll let you know what I find when I look inside.

reddesert · Feb 10, 2023

The photos really help. I believe, from these photos, that your helicoid is at or almost at the removal position. It might be a little cockeyed, in the photos it looks like the right side is a little further out than the left, but I can't tell if that's real. You should be able to tell. My guess is that it's a bit jammed in its mount and the jam is what's holding it to the camera, not the bayonet flanges.

The focus mark and DOF scale are on the same piece of chrome metal as the helicoid's bayonet flanges, so even if other bits of the helicoid were assembled funny, the focus mark position is a clear sign that it is at or almost at the removal position, not the mounted position.

For reference, here are two pictures inside my S2 helicoid. The first shows the fully-mounted position with the DOF mechanism at 3 o'clock.

The second shows the helicoid twisted almost to the removal position. This looks more like yours, note the position of the DOF mechanism and the upper lens bayonet flange. There is a light baffle illuminated by the flashlight at about 4:30 here, 6:00 when fully mounted, that is absent in your photos. I don't know if this is missing from your helicoid or there were different versions. Both this baffle and the DOF mechanism are screwed to the helicoid from the back, and I suppose someone could have taken the pieces apart and not gotten them back together correctly. However, the position of the focus mark, lens bayonet, etc suggest that your helicoid is close to removal, so it isn't the release mechanism that it is holding it on. Maybe some out-of-roundness in the mount, or some little piece is loose (although I'm not sure if there is a piece that would be a viable suspect).

hsandler · Feb 18, 2023

I am in Ottawa, and I have an S2, helicoid and lenses as well as aTelemore converter. You can arrange with me to see it if that would help you figure out what’s wrong with your helicoid.

ThomasW · Feb 18, 2023

H Sandler: Thank you for this offer. My schedule for the next several days is already "spoken for" but this could well be helpful. My Tuesday afternoon on this upcoming week is open as is Thursday morning and afternoon. After that it could be anytime including the evening on Friday. Does any of this work for you? If not, perhaps the follwoing week.

MattKing · Feb 19, 2023

It would probably make more sense if hsandler started a Private Conversation with ThomasW to discuss the details.
Although ThomasW has a post count that is too low to start one up, if hsandler starts it, ThomasW can fully respond and participate in it.

ThomasW · Feb 19, 2023

This works for me. Thank you. My reply to hsandler was as circumspect as possible as I realized that Photrio has some protocols and restrictipns regarding Private Conversations.

itsdoable · Feb 19, 2023

A little late, but maybe this will help.

I don't have a C, but several versions of the S.

The Helical appears to be in the unlocked position already, maybe try to work it strait off, or try to rotate it clock wise to the locked position. The infinity mark when focused to infinity should be at about 1:30 when the helical is properly mounted. To dismount the helical, you rotate it counter clock wise until the infinity mark is top dead center (12:00). It explains why the release button is depressed, and the stop down is disengaged. It's either seized in that position, or someone glued it there?

ThomasW · Feb 19, 2023

Thank you for this. I've tried to wiggle it loose as a previous writer noticed that it's already either at or near the cusp of being loose. Yours is the first observation though that it is perfectly normal that the release button could not be depressed if the lens is in this position. I try wiggling it some more, but it seems to be holding tightly currently.

hsandler · Feb 19, 2023

MattKing said:
It would probably make more sense if hsandler started a Private Conversation with ThomasW to discuss the details.
Although ThomasW has a post count that is too low to start one up, if hsandler starts it, ThomasW can fully respond and participate in it.

Understood, thanks.

itsdoable · Feb 19, 2023

ThomasW said:
... Yours is the first observation though that it is perfectly normal that the release button could not be depressed if the lens is in this position...

the release button should be depressed when the focus helical is in this orientation, but there should still be some play in that button. if it is immobile, then something is probably jammed.

Spot V · Nov 22, 2023

ThomasW said:
Thank you for this. I've tried to wiggle it loose as a previous writer noticed that it's already either at or near the cusp of being loose. Yours is the first observation though that it is perfectly normal that the release button could not be depressed if the lens is in this position. I try wiggling it some more, but it seems to be holding tightly currently.

Hope that focusing helical came off by now.
Just a small observation: the release button can be depressed, no matter what position the focusing helicoid is in - as long as the camera is in double exposure mode.

ThomasW · Nov 22, 2023

Thank you for this advice. I tried this with the camera in Double Exposure mode; the Release Button will still not depress. I am really convinced that some previous owner did something strange to this camera. About 6 months ago, I gave up and found another Model C in good shape and have been using it successfully. Your advice does work on that second camera, although I don't need it to do so as the Release Button on this second camera works properly anyway. I am quite pleased with my photographs from this second Bronica. I guess I may as well keep the first one as a parts supply for the second one should I ever need parts. This is rather a sad outcome for an otherwise nice piece of kit. Ofc ourse, If anyone else has any bright ideas, I'm keen to try them.

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