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Alex
Rating: N/A
Votes: 0 (Vote!) | | Posted on Saturday, March 19, 2005 - 07:33 pm: | 
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I couldn't figure out at first why, when I mounted almost any lens on my Yashica 108 body, the lens was always slightly stopped down at any setting other than widest aperture. I'd mount an f/1.8 lens, and setting it to f/2 or narrower, the aperture blades would move in slightly. I think I've worked out why. Looking at the lens mount from the front, there's a little lug at around the 6 o'clock position which mates with a lever on the lens, and on tripping the shutter, the lug moves rapidly to the left, so that the lens lever follows, thus stopping down the lens. The 'resting' position for the lug keeps the lens at 'full bore', or should. On the Yashica 108, this lug is on a ring the diameter of the lens mount, and the ring is partly toothed, mating with a toothed wheel which spins when the shutter release is tripped, so that the ring with the lug is spun clockwise, thus letting the lens stop down.
Comparing the resting position of this lug with similar lugs on other Yashicas, like the FX3/FXD, the lug on the 108 is a fraction to the left (face-on) of the equivalent lug on these others. It's not a misalignment of the ring the lug is on, because the partially-toothed edge mates properly with its driving cog at exactly the right position. So it seems to me that I need to add a little metal of some kind to the right-hand-side of the lug to extend it in that direction. (I hope I'm making sense here!)
What I'd like to know is the best way to approach this. A small blob of solder perhaps? I don't know if this is a common problem with the 108, and perhaps someone else has encountered this (or similar) and can offer suggestions. |
Mike
Rating: N/A
Votes: 0 (Vote!) | | Posted on Monday, March 21, 2005 - 01:36 pm: |
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Hi Alex-
I would recommend removing the chrome lens ring and taking a look at the gearing on the outer black ring. It may have just slipped a notch in the gears or there may be some obstruction. If there is no obstruction, adjusting the gearing is pretty straightforward. |
Alex
Rating: N/A
Votes: 0 (Vote!) | | Posted on Tuesday, March 22, 2005 - 05:25 pm: |
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Mike,
Thanks for the suggestion. I took the chrome ring off and there's a small strip of gearing on the outer black ring which meshes with a toothed wheel. In the rest position, it meshes exactly at what looks like the right place, at the leftmost end of the strip of teeth on the black ring. I loosened two of the three jockey wheels which keep the black ring in place when it's moving to follow the toothed wheel, and made sure it was properly seated. It's seated OK. Some lenses work fine, others display the partial-stopping-down effect, but all lenses work fine on all my other Y/C bodies. I wondered if this might be a design issue with this model. |
Mike
Rating: N/A
Votes: 0 (Vote!) | | Posted on Tuesday, March 22, 2005 - 05:49 pm: |
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Hi Alex-
Sounds like the gearing is OK. The camera needs to overcome the spring tension built into the lens, and this may vary from lens to lens. Perhaps the spring tension in the camera is a bit weak for some of your lenses. I would also look at the metal tab on the outer ring which is bent back to engage the tab on the inner ring which actually engages the lens tab. It should go straight back. Can you manually move the inner tab to the right any farther?
I don't think your problem is an issue with this model, I've repaired and used several Yashica 10* and TR7000 models which are all similar. |
Alex
Rating: N/A
Votes: 0 (Vote!) | | Posted on Thursday, March 24, 2005 - 07:47 am: |
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Mike,
That's a good point. Just to make sure I've understood you here: looking at the lens mount throat from the front, there is an outer ring which rotates when the shutter is released. This ring moves clockwise, and hence the metal tab on it (at 6 o'clock) moves round to about 8 o'clock, thus releasing the tab on the lens which in turn will stop down, then catches it on the way back to open the lens again. Just behind this tab on the camera's outer ring, there is another tab, shifted a little to the left. It does not move when the shutter is released, though with a pencil tip I can move it to the right, then it springs back. So now I'm wondering if it should be this rearmost tab (closer to the mirror) which should be engaging with the tab on the lens. Using a cocktail stick as a rough guage, the distance of this rear tab from the flush surface of the lens mount is pretty well exactly the same as the distance of the tabs on my other Y/C bodies (FX, RTS etc), and a fraction less than the extent to which the tab on the lens itself stands proud of the flush surface of the lens mount. (I hope I'm making sense here.) Both the tabs inside the camera are upright, and if I understand you correctly, the forward tab should be bent back to hold the inner tab in its own under-tension position, and it's the inner tab, not the outer tab, which should be controlling the lens diaphragm. Holding the rear tab to the right, it occupies the same position as my FX-3's tab does in its rest position, but to get the forward tab bent back to hold it in place, I'd need to release the jockey wheels and re-position the teeth on the strip against the toothed wheel by one or two teeth, which should be easy. Am I on the right track?
(It's beginning to look as if the person I bought the camera from had been fiddling with it.) |
Mike
Rating: N/A
Votes: 0 (Vote!) | | Posted on Friday, March 25, 2005 - 11:28 am: |
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Hi Alex-
Yes, the frontmost tab (metal) should bend back and engage the rearmost plastic tab just to it's left. It should hold it in the correct resting position.
I've seen these tabs and also the metal F-value tab at about the 1 o'clock position bent out of shape, probably by someone attempting to insert a lens incorrectly, or possibly an incorrect lens.
I'll see if I have a photo of this in correct alignment. |
Alex
Rating: N/A
Votes: 0 (Vote!) | | Posted on Friday, March 25, 2005 - 02:23 pm: |
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Mike,
A photo would be ace. Thank you for all the patient help, this has explained everything, the variability of the effect between different lenses, the tab that 'appeared' to do nothing, and all the scratching and coating loss on the frontmost tab. I know so much more now than I did a week ago, and I do so appreciate the friendly expertise so freely given on this gem of a forum.
Alex |
Mike
Rating: N/A
Votes: 0 (Vote!) | | Posted on Saturday, March 26, 2005 - 07:46 pm: |
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Still looking for photo- stand by. Might take another day or two.
Mike |
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