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09-01-2011, 10:47 AM   #1
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Help! Old M-series pancake lens issue!

So I have this old M-series 40 mm pancake from my LX (I use it on my DSLR as well) that hasn't been working for a while. This morning I tried to figure out what was wrong with it, only for the optics to come unscrewed. Turns out that it comes in three parts: the optics, focus ring, and aperture ring. I've managed to get either the focus and optics back together, or the focus and aperture, but I can't seem to get all three properly in place. It seems like if the optics came out, they should be able to go back in without the use of any special equipment, but I don't know for sure. Has anyone had something like this happen to them before?

09-01-2011, 01:35 PM   #2
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It sounds to me like the close-focus stop broke and the lens helix became "free" and unscrewed.
The way to assemble it is to remove the bayonet flange from the bottom, and then screw in the focus ring helix followed by the lens assembly helix. The three parts must be screwed-in at precise thread counts and angle so that the aperture lever in the body mates with the aperture mechanism in the lens assembly, AND the lens has both correct infinity and close focus.

Not an easy task if you have not done this before, but with lenses as simple as the -M 40 it can be done.

You should also figure out why the lens failed in the 1st place and repair that as well - perhaps someone with more intimate experience with the -M 40 can chime in (I have a similar lens, the DA-40 which fortunately has not had to be opened yet).

Feel free to post some pictures of the carnage.

Whatever you do, don't throw it out ... it's likely fixable.

Last edited by photocanadian; 09-01-2011 at 07:12 PM.
09-01-2011, 02:31 PM   #3
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I've tried repairing a Cosina 24mm prime recently and ended up ruining it. There was some crunching, and then the focus ring no longer turned. Could not get the thing back together. The trouble with this stuff is that there are options on how to put it together. Often in stuff on the web, people say "score" the parts before taking them apart, so you can get them correctly aligned. In the UK, the M 40mm is GBP 70, whereas a service is about GBP 30.

As the M40mm is worth more than the cost of sending it in to be fixed....I'd get a quote and send it to a repair guy. Thats my 2 cents...practice on an old M 2/50 first before mashing old threads up on such a nice lens as the M 40mm.

I had that lens in the past, only got rid of it because of the long focus distance, but I always found it to be superbly sharp, equal or better than the M 1.7/50, contrary to reviews here or on Stan's website.
09-02-2011, 07:47 AM   #4
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Thanks, I'll try taking the bayonet flange off The reason it broke is because it's 35 years old and has been on every continent but antarctica. I'd like to send it in to the shop, but I'm 16 and completely broke...

09-02-2011, 10:18 AM   #5
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QuoteOriginally posted by ZoeB Quote
Thanks, I'll try taking the bayonet flange off The reason it broke is because it's 35 years old and has been on every continent but antarctica. I'd like to send it in to the shop, but I'm 16 and completely broke...
It's probably not necessary to take the mount off at this point. Here are some photos of my lens and what I think happened. The first photo shows the trim ring removed, which will expose six screws. The trim ring unscrews counter-clockwise. Find something round and rubber that you can press against it for a friction grip, without touching the front lens element. Then you need a small screwdriver for the three screws that aren't in cutouts. That allows you to remove the filter ring. The photo shows two of these screws removed. The filter ring should come right off but because this lens is a pancake, it's thin. If you can't get a grip on it, screw a filter into it and that will stick out enough to grab.



More screws are now visible. The inner three screws hold the entire optics (front and rear lens groups plus aperture) to the focusing helix. You only need to remove them if it makes you nervous to work around them. (A simple alignment is necessary if you remove this assembly.) The outer three screws attach the focus ring to the helix.



The focus ring is removed here. Now you can see the steep coarse threads like the ones you've been trying to screw back together. Also, there's a small slotted screw just inside of the orange diamond. That's the stop screw for the focus ring. Your stop screw might be missing, or a couple of the focus ring screws were really loose. That allowed the focus ring to turn past its stops and unscrew the helix.



I counted six possible start points for the coarse helical threads. The aluminum ring on the lens body also has fine-pitched threads. When that aluminum ring is screwed all the way in, that's just a little past infinity focus - there is maybe 5 degrees extra for adjustment room. The helix needs to be reinstalled starting at the other end of the focus travel, so turn the ring about 95 degrees clockwise, then maybe another 5 degrees more to give the threads room to engage. I don't know of any way to do this besides trial and error. Screw in the optical part, and see if all the parts line up in the right place. If they don't, rotate 60 degrees and try again.

With some lenses, it's not that simple. There are guides to move the optics straight in and out. It may be necessary to remove the mount to access those parts. The main ideas are to set the aluminum ring in the right starting spot and trial and error for the helix.
09-02-2011, 12:32 PM   #6
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You are probably right, however on most lenses I find it makes it easier as there is one less thing to "bulls-eye" (the aperture mechanism) when the rear mechanism can be seen.

And I'm no beginner when I comes to screwing up (and un-screwing-up) lenses

QuoteOriginally posted by Just1MoreDave Quote
It's probably not necessary to take the mount off at this point. Here are some photos of my lens and what I think happened. The first photo shows the trim ring removed, which will expose six screws. The trim ring unscrews counter-clockwise. Find something round and rubber that you can press against it for a friction grip, without touching the front lens element. Then you need a small screwdriver for the three screws that aren't in cutouts. That allows you to remove the filter ring. The photo shows two of these screws removed. The filter ring should come right off but because this lens is a pancake, it's thin. If you can't get a grip on it, screw a filter into it and that will stick out enough to grab.



More screws are now visible. The inner three screws hold the entire optics (front and rear lens groups plus aperture) to the focusing helix. You only need to remove them if it makes you nervous to work around them. (A simple alignment is necessary if you remove this assembly.) The outer three screws attach the focus ring to the helix.



The focus ring is removed here. Now you can see the steep coarse threads like the ones you've been trying to screw back together. Also, there's a small slotted screw just inside of the orange diamond. That's the stop screw for the focus ring. Your stop screw might be missing, or a couple of the focus ring screws were really loose. That allowed the focus ring to turn past its stops and unscrew the helix.



I counted six possible start points for the coarse helical threads. The aluminum ring on the lens body also has fine-pitched threads. When that aluminum ring is screwed all the way in, that's just a little past infinity focus - there is maybe 5 degrees extra for adjustment room. The helix needs to be reinstalled starting at the other end of the focus travel, so turn the ring about 95 degrees clockwise, then maybe another 5 degrees more to give the threads room to engage. I don't know of any way to do this besides trial and error. Screw in the optical part, and see if all the parts line up in the right place. If they don't, rotate 60 degrees and try again.

With some lenses, it's not that simple. There are guides to move the optics straight in and out. It may be necessary to remove the mount to access those parts. The main ideas are to set the aluminum ring in the right starting spot and trial and error for the helix.
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