How to Strip and Clean a 29mm Pentacon M42 Lens
Set out your workspace.,Focus your lens to its shortest distance., Remove the front cover., Remove the front element retaining ring., Remove the front element for cleaning later., Remove the second-to-front-element., Unscrew your front aperture...
Step-by-Step Guide
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Step 1: Set out your workspace.
Set out at least two pieces of clean, white paper for you to put things on.
Give yourself plenty of space to work with.
Pour out some denatured (preferred) or rubbing alcohol or other similar fluid into a small glass. ,, Grip the focusing barrel, grip the front cover and twist the latter counter-clockwise.
You may find this needs more force than you think. , This unscrews counter-clockwise.
Use a special tool for this purpose if you have one; otherwise, grip the lens firmly and use a screwdriver to push it.
This can be extremely stiff.
Be very careful; slipping and gouging your front element with a screwdriver would lead to a very sub-optimal state of affairs., With the retaining ring above gone, this will simply lift out Place it on a soft cloth the right way up. , This is threaded into place; you can remove it the same way you did the front element retaining ring above. , You can see this when you look down into the front lens barrel; it's held in place with three screws.
Undo these and keep them safe. , You might want to use a magnetic screwdriver to lift this out. , This will lift out easily.
Now turn this upside down, and we're going to go to the rear of this. , This is another of those "jam a screwdriver in and pray" notched rings.
As before, be careful., This will drop out quite easily.
Put it somewhere safe, and remember which way it came out!, This is the black part of the body in which the last group you removed sat.
Now, turn what's left of your lens rear-upwards.
You will notice that there are three, very small grub screws near the top.
Remove one of these
-- you only need to do one to free the housing, and undoing all of them may or may not make this part tricky to re-align.
If you don't need to undo it all the way, don't.
These screws are extremely fiddly to re-fit.
Otherwise, put the screw somewhere safe
-- these are extremely easy to lose., This is held into place along with a retainer with two holes in it.
You might get lucky and be able to jam a nail into one of these holes and turn it, but the farm should not be bet on such.
If you have a pair of circlip pliers, these will work much better.
Unscrew it counter-clockwise and drop it out. , Immediately underneath the small grub screws holding the second group's housing in place (one of which you unscrewed earlier), you will see one more, even smaller grub screw.
Loosen this.
Again, don't remove this all the way if you can possibly avoid it.
This is even smaller and fiddlier to re-fit than the last one you removed, and even easier to lose., This should simply screw out counter-clockwise; removing this will expose your aperture blades. , You'll need to refer to this later., Be very very careful about how you do this.
Aperture blades are, as you will notice, extremely thin and very easy to bend.
You may find it useful to lift out the rear aperture guide, complete with blades, and simply drop them into your glass of alcohol.
But if you lift them out individually, do so very carefully with tweezers or a magnetic screwdriver.
If you're using the latter method, then remove the rear aperture guide too. , If they're not too bad at all, then blow any large particles away with a blower brush, and use a soft, lint-free lens cloth to polish them.
Otherwise, contact lens cleaning fluid might do the trick.
Place them somewhere safe and clean. , Wiping them with some alcohol and a dust-free cloth should do the trick., This was the one you removed earlier, which was held in place with three screws.
Don't do these screws up tight yet. , The holes in the latter should roughly line up with the slots in the former. , Allow them to dry naturally; placing them directly under a lamp should help to evaporate the alcohol., Get a cup of tea or coffee and a snack, some fresh air, and a smoke if you're that way inclined.
Seriously, you'll need it., This is the most difficult, time-consuming part of the rebuild.
Refer to the diagram/scribble you made earlier and take your time.
Use tweezers to put them back into place.
When you find yourself having to slide one aperture blade under another, you may find that lifting the latter with a magnetic screwdriver helps, too.
Remember that bending or breaking one of these could make your lens a write-off, so be careful.
Take breaks as often as you need to. ,, Fasten the grub screw you undid earlier when you're done.
Open and close the aperture again to make sure everything is okay. , This is exactly the opposite of undoing them; there should be no surprises.
Use a lens cloth to clean them both before and after fitting., You'll notice that the aperture lever should, on auto lenses at least, line up with a prong inside the lens body.
Push your stop-down button (or aperture pin on M42 lenses) to ensure that the aperture is opening and closing properly., Stop the lens all the way down to f/22 with the aperture ring on the body, and hit the stop-down button.
You'll pretty much have to guess what looks right and what does not; wide-open, the aperture should not obscure the rear elements too much (if at all), and stopped down, it should not be a tiny pinhole.
Adjust the front aperture guide ring until it looks right.
When it does, tighten the three screws that hold it in place., Again, there should be no surprises doing this; it's the opposite of removing them.
And again, clean your groups twice, once before fitting and once right after doing so.
Re-fit your front cover, too. , Make sure that your lens focuses and stops down properly.
If it doesn't focus properly, you may have gotten one of the groups fitted the wrong way around; if it's sticky stopping down, you may have contaminated your aperture blades with dust, hair or something else. -
Step 2: Focus your lens to its shortest distance.
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Step 3: Remove the front cover.
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Step 4: Remove the front element retaining ring.
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Step 5: Remove the front element for cleaning later.
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Step 6: Remove the second-to-front-element.
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Step 7: Unscrew your front aperture guide ring.
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Step 8: Remove your front aperture guide ring.
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Step 9: Separate the front barrel from the lens body.
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Step 10: Remove the rear element retaining ring.
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Step 11: Remove the rear group.
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Step 12: Remove the group's housing.
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Step 13: Remove the last element.
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Step 14: Loosen the rear aperture retainer's grub screw.
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Step 15: Remove the rear aperture retainer.
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Step 16: Make a quick drawing of how your aperture blades interact with each other.
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Step 17: Remove your aperture blades and place them in your alcohol.
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Step 18: Clean your optical elements.
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Step 19: Clean out your housing and your aperture blade guides.
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Step 20: Refit your front aperture guide.
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Step 21: Drop your rear aperture guide into place.
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Step 22: Remove your aperture blades from the alcohol.
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Step 23: Take a break.
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Step 24: Re-fit your aperture blades.
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Step 25: Verify that the aperture opens and closes correctly by moving the lever on the side back and forth.
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Step 26: Re-fit your rear aperture retainer.
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Step 27: Re-fit your rear groups.
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Step 28: Open your aperture fully and drop your front barrel into your lens body.
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Step 29: Check your apertures again.
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Step 30: Re-fit your front elements
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Step 31: ensuring that you put the groups back in the right way up!
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Step 32: Take your camera out and get some photographs.
Detailed Guide
Set out at least two pieces of clean, white paper for you to put things on.
Give yourself plenty of space to work with.
Pour out some denatured (preferred) or rubbing alcohol or other similar fluid into a small glass. ,, Grip the focusing barrel, grip the front cover and twist the latter counter-clockwise.
You may find this needs more force than you think. , This unscrews counter-clockwise.
Use a special tool for this purpose if you have one; otherwise, grip the lens firmly and use a screwdriver to push it.
This can be extremely stiff.
Be very careful; slipping and gouging your front element with a screwdriver would lead to a very sub-optimal state of affairs., With the retaining ring above gone, this will simply lift out Place it on a soft cloth the right way up. , This is threaded into place; you can remove it the same way you did the front element retaining ring above. , You can see this when you look down into the front lens barrel; it's held in place with three screws.
Undo these and keep them safe. , You might want to use a magnetic screwdriver to lift this out. , This will lift out easily.
Now turn this upside down, and we're going to go to the rear of this. , This is another of those "jam a screwdriver in and pray" notched rings.
As before, be careful., This will drop out quite easily.
Put it somewhere safe, and remember which way it came out!, This is the black part of the body in which the last group you removed sat.
Now, turn what's left of your lens rear-upwards.
You will notice that there are three, very small grub screws near the top.
Remove one of these
-- you only need to do one to free the housing, and undoing all of them may or may not make this part tricky to re-align.
If you don't need to undo it all the way, don't.
These screws are extremely fiddly to re-fit.
Otherwise, put the screw somewhere safe
-- these are extremely easy to lose., This is held into place along with a retainer with two holes in it.
You might get lucky and be able to jam a nail into one of these holes and turn it, but the farm should not be bet on such.
If you have a pair of circlip pliers, these will work much better.
Unscrew it counter-clockwise and drop it out. , Immediately underneath the small grub screws holding the second group's housing in place (one of which you unscrewed earlier), you will see one more, even smaller grub screw.
Loosen this.
Again, don't remove this all the way if you can possibly avoid it.
This is even smaller and fiddlier to re-fit than the last one you removed, and even easier to lose., This should simply screw out counter-clockwise; removing this will expose your aperture blades. , You'll need to refer to this later., Be very very careful about how you do this.
Aperture blades are, as you will notice, extremely thin and very easy to bend.
You may find it useful to lift out the rear aperture guide, complete with blades, and simply drop them into your glass of alcohol.
But if you lift them out individually, do so very carefully with tweezers or a magnetic screwdriver.
If you're using the latter method, then remove the rear aperture guide too. , If they're not too bad at all, then blow any large particles away with a blower brush, and use a soft, lint-free lens cloth to polish them.
Otherwise, contact lens cleaning fluid might do the trick.
Place them somewhere safe and clean. , Wiping them with some alcohol and a dust-free cloth should do the trick., This was the one you removed earlier, which was held in place with three screws.
Don't do these screws up tight yet. , The holes in the latter should roughly line up with the slots in the former. , Allow them to dry naturally; placing them directly under a lamp should help to evaporate the alcohol., Get a cup of tea or coffee and a snack, some fresh air, and a smoke if you're that way inclined.
Seriously, you'll need it., This is the most difficult, time-consuming part of the rebuild.
Refer to the diagram/scribble you made earlier and take your time.
Use tweezers to put them back into place.
When you find yourself having to slide one aperture blade under another, you may find that lifting the latter with a magnetic screwdriver helps, too.
Remember that bending or breaking one of these could make your lens a write-off, so be careful.
Take breaks as often as you need to. ,, Fasten the grub screw you undid earlier when you're done.
Open and close the aperture again to make sure everything is okay. , This is exactly the opposite of undoing them; there should be no surprises.
Use a lens cloth to clean them both before and after fitting., You'll notice that the aperture lever should, on auto lenses at least, line up with a prong inside the lens body.
Push your stop-down button (or aperture pin on M42 lenses) to ensure that the aperture is opening and closing properly., Stop the lens all the way down to f/22 with the aperture ring on the body, and hit the stop-down button.
You'll pretty much have to guess what looks right and what does not; wide-open, the aperture should not obscure the rear elements too much (if at all), and stopped down, it should not be a tiny pinhole.
Adjust the front aperture guide ring until it looks right.
When it does, tighten the three screws that hold it in place., Again, there should be no surprises doing this; it's the opposite of removing them.
And again, clean your groups twice, once before fitting and once right after doing so.
Re-fit your front cover, too. , Make sure that your lens focuses and stops down properly.
If it doesn't focus properly, you may have gotten one of the groups fitted the wrong way around; if it's sticky stopping down, you may have contaminated your aperture blades with dust, hair or something else.
About the Author
Catherine Stevens
Dedicated to helping readers learn new skills in lifestyle and beyond.
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