Leaf Shutter CLA

Rick Oleson



Leaf shutters all share a basic design principle and layout, but there are a number of detail differences from one brand to another (and sometimes even within a single brand – Compur in particular, having been in production for so many years, appears in a number of variations).

In the interest of providing a useful amount of detail, this article will deal with a specific example, a small Synchro Compur which happens to be mounted with a Schneider Super Angulon for large format use. In details where other variations in design are common, I will try to point those out as we go along.

There are, however, a few more major variations in design which are worth mentioning up front as they can complicate things considerable and may be better left alone until you have gained more experience: The first of these is the concealed shutter mounting used in Rolleiflex and the numerous other TLR models which are copies of the Rollei to a greater or lesser extent. The need to remove leatherette, disconnect and realign shutter and aperture control dials, desolder flash synch wiring, etc in some of these examples can increase the magnitude of the job. Once gotten used to, however, these are not usually too unpleasant a task, and the following study is fully applicable once you have the front fascia out of the way. The second category of variation is the shutter module found on any of a large number of 35mm rangefinder cameras from the late 1960s and early 1970s. These tend to be complicated primarily by the incorporation of the light meter cell into the front of the shutter and the cosmetic housings which can lead to considerable complication – in some cases, the shutter must be removed from the camera and the disassembly and reassembly process can be quite tedious in relation to the value of the camera. Along similar lines, I would caution against overconfidence in attacking a unit-focusing Zeiss Contaflex; not only are these devilishly difficult to get apart and properly back together, but more often that not the problem is as much in the winding system as in the shutter itself and a perfectly CLA'd shutter may cease to function after reinstallation in the body (this does not apply to the front-cell-focusing models, at least in my experience).



Note: Many of the tools and supplies needed are available from Fargo Tools at www.micro-tools.com. You may also find them or good substitutes closer to home. If you need something that you can't find elsewhere, it's a good bet that Fargo has a good one.

The tools involved in servicing a leaf shutter are pretty basic:

For a workspace, a smooth table in a well lighted area is sufficient (I once repaired a shutter on the tray table of an airliner in flight, but I don't recommend it – it's embarrassing when a spring flies over the seat back into another passenger's hair). Spread a length of paper towel across the table as a work surface, and tape it down before you start.

Also, keep a pad of paper and a pencil handy, and ideally also an SLR camera with a close-focusing lens to help you document what you're doing as you go. Keep good notes and use the camera when a sketch would be too difficult or tedious. In particular, a good photo of the front of the shutter just after all the covers come off can be invaluable should a spring or other small part go flying before you took clear notice of exactly where it was.



The shutter we're going to deal with has a unit-focusing lens in it. If you have a front-cell-focusing lens, there's an extra step or two which I will mention here. You're going to have to remove the focusing unit, and this will require you to refocus the lens on reassembly. We'll deal with refocusing at the end, but before you start you should know that you'll need a piece of glass big enough to span the film gate, and a good SLR camera to reset the focus (some people have more sophisticated tools, but these will do the job).

The focusing ring usually carries the distance markings and the infinity stop, and is attached to the front lens cell with set screws. Remove these set screws and pull off the ring. Mark the top center of the front cell with a scribe or marking pen, and unscrew the cell. Count the turns as you go, and note the location of the mark as the cell comes free of the thread: these are important because the thread has more than one starting point, and you will want to reassemble it on the same thread that it was on before so it comes out right side up. From this point on, the shutter is like the one we're discussing. The second element is still in the shutter.

Now to the work at hand: Remove the front cell of the shutter by gripping it with either the rubber pad or a strip of masking tape and turning counterclockwise. If the shutter is not in a camera, remove the rear cell in the same way. If it is mounted in a camera, you will probably have to use a spanner wrench. It is not impossible to clean the shutter with the rear cell in place, but it's best to keep the lens surfaces clean if you can (which basically requires removal). Most lens surfaces, coated or uncoated, can be cleaned with conventional lens cleaner and tissue; however, a number of early coated lenses had inner coatings so soft that any contact with a lens tissue would visibly damage the coating. In these cases, the first spot of fluid or dirt on an inner lens surface means the end of the coating on that element. It's better to get them away from the action early.

Having placed the lens cells safely aside, you will find a threaded collar around the hole where the front cell had been. This generally has a series of notches around its edge, in one of which is either a screw head or a small disk with two spanner holes and with one side flattened. Remove the screw, or rotate the disk with your tweezer points so that the notched collar can turn. Now unscrew the collar counterclockwise, and place it next to the front cell with the screw in its center so it can't roll away.

Under the collar is the front fascia plate. This is usually attached by two screws, one on either side of the lens; in our case, however, it was secured only by the collar so it's now free to lift off. Under this plate is the shutter speed ring, which is the knurled chrome ring that you turn to set the speeds, and the shutter speed cam, an irregularly perforated disk which actually moves the levers to control the speeds (in some cases these are a single part; in our Compur, they are separate and engage each other by means of a tab and notch). Often (as in our case), the click stops for the speeds are provided by a bump on the cam engaging grooves in the back of the fascia plate. Some designs use other devices, some of which may involve small loose parts which you must watch out for. The speed cam and the back surface of the fascia plate are usually dirty and sticky – clean them well with lighter fluid on a paper towel and set them next to the retaining collar and front lens cell.

With these parts removed, we are now looking into the shutter, directly at the gears and levers. On top, though, there is still the cocking rack. This is a ring around the lens mounting thread, usually having a set of gear teeth cut into its outer edge along one side, and also having an extension coming out from it which goes out past the outer housing of the shutter and usually ends with the little knob that is gripped for cocking the shutter (in some designs, there is no handle on it as it is mechanically operated). Note that the gear rack engages a small gear which has teeth most, but not all of the way around, and also note that the number of teeth on the gear corresponds to that on the cocking rack. You will want to make sure that these are properly matched up on reassembly. The small gear is attached to the main driving spring of the shutter, which it winds by rotation of the cocking rack. Some shutters, particularly older ones and those with a slower top speed, do not have these gears: in these, there is a simple extension spring attached to the underside of the rack which serves as the main driving spring.

In either case, there is a spring running from a post on the underside of the rack to another in the shutter chassis. Leave the one end attached to the rack, but use your spring tools to remove the other end from the chassis – note the location of the anchor pin. remove the rack and spring, clean them and place them next to the speed cam. In this particular shutter, it is necessary to lift out the shutter release lever in order to reach the spring anchor. The shutter release has a small hair spring around its axis – carefully note its orientation before removing it, and place it aside next to the rack (this is not necessary in every design).

You now have access to the shutter timing gears, but there's still a bit of a trick: there are actually two gear sets which look quite similar. One is the shutter timing gears, the other controls the self-timer and the flash synch delay. The quickest way to determine which is which is to either see which gears are affected by movement of the speed cam (easily placed back on the shutter for the purpose), or to move the self timer lever and see which gears move. Having figured that out, let's go for the shutter gears first.

We have an advantage with this Compur, and I advise taking advantage of it in this case: the gearset is a module, held in by 2 screws: one through the axis of a post at one end, the other through the bottom flange of the assembly. By removing these two screws, we can lift out the whole module and dunk it in solvent. I find that a plastic 35mm film canister makes a good bathtub for this purpose. Drop the module in, fill the can about halfway up, put the lid on tight and shake it for a little while. Then take it out and set it aside with its screws to dry. Not every shutter is so accommodating, however: some are not modular and will spill individual gears if these same screws are removed, so use caution as you go. If it looks like the top plate wants to come off the timing assembly, put the screws back in before the gear shafts get dislodged or you'll have a busy evening getting it all back together. We can clean it without removing it from the shutter.

To clean the gears in place, you will want the draftsman's pen. First determine the location of the pallet – this is the little sort of pendulum that oscillates back and forth and causes the buzzing sound at slow shutter speeds. Starting with this shaft, dip the pen in lighter fluid and touch its tip to the bearing at the top of the shaft where it comes through the plate, and again at the bottom end where it goes into the bottom plate. You should see a noticeable improvement in the shutter's operation just form this – if it has been stuck midway it should immediately complete its cycle. Now go to the next shaft, the star wheel that the pallet engages, and do the same. Follow in this order, from one gear to the next. Once you're one or two shafts past the star wheel, there is probably enough spring power that a little dirt in the bearings has no effect. Repeat this process with the self-timer gearset, which works in basically the same way.

Before going on, inspect the shutter blades for signs of oil or dirt on the surface. Because there is so much surface area contact, it doesn't take much to make two blades stick together and stop the whole show. If they're not clean and dry, clean them with lighter fluid on a damp Q-Tip. Try not to let fluid wick between the blades, as it can take a long time to dry and may get into places it doesn't want to be. If the blades have anything more than a very slight residue, you really ought to remove them and clean them individually… but I think that might be better saved for another episode, as it can get complex. If you have blades wanting to stick, and you're not up to that degree of disassembly, you may fix it with a puff of fine graphite powder applied directly to the blades and worked in through operation of the shutter. This MUST be done with both lens cells out, however, and many cycles will be needed to get all the stray powder out before reassembly. The specks on the inside lens surfaces don't really do any harm, but they are VERY visible through the lens, due to the magnification of the lens elements. There may be cases in which this is the only practical solution to sticking blades, due to complexity of the shutter's construction.

Now that the shutter is clean and dry, it's time to begin reassembly. First, reinstall the timer gear module. In most cases, one of its mounting holes is oversize to allow for some adjustment of the timing by sliding the gear assembly closer to or farther from the cocking rack. Just get it in place for now, adjustment will come later.

Next reinstall the cocking rack, attaching its little return spring and making sure the mainspring gear is properly meshed. For the moment, leave the speed control ring and cam off. Holding the rack in place to keep the gears in mesh , cock and release the shutter several times. The speed you will get with the cam off is sort of a combination of one second and B: the timer will run out for a second, but the shutter won't close until you take your finger off the release lever. The one second should run smooth and clean, without hesitation. If it does, I wouldn't recommend lubrication unless this shutter expects to see heavy use. If it's going to spend most of its time on the shelf and be expected to work well when picked up later, it will suffer more from old lubricant than it will from wear.

If it does not run perfectly crisp, and you're sure everything is clean, then you will want to apply exactly two drops of oil: one to the pallet shaft, and the second to the star wheel shaft. For oil, the light shutter oil sold at Fargo is good, but I use something closer at hand: slightly modified WD-40. Before casting me into the Pit, please hear me out: if you squirt a small amount of WD-40 into a small jar (I use a 1/4 ounce model paint jar) and leave it, you will see that it settles out, becoming clear at the top and cloudy at the bottom. You don't want the sediment, but the clear stuff at the top is a very fine oil with excellent lubricating properties. By keeping this jar handy and not shaking it up, you can dip your oiler (née drafting pen) into it at the top and get just what the doctor ordered. If this makes you uncomfortable, just get some good shutter oil. The main thing is that it be very thin, as most oils will stop these little parts cold.

Everything should now be zipping along nicely. Check the self timer for smoothness, and follow the same procedure with it.

From here, it's just a matter of getting it back the way you found it. When you set the speed cam in place, rotate it back and forth through its range of travel to give the levers a chance to drop into their proper slots. If the shutter is stuck after reassembly, the most likely reason is one of these levers missing its slot and jamming under the plate. You'll also see that the speed-setting ring engages the edge of the cam via a couple of tabs and notches – it can only go one way. Once those are in, it's time for the fascia plate. If this has a set of grooves in the back for the speed detents (as it does in our case), lubricate this grooved area lightly with white grease before reinstalling the plate. Now set the fascia plate in place – it too can only go one way, as one or two pins from the shutter chassis will protrude to engage holes in the back of the plate. Don't put the retaining ring back on yet, just hold it all together with your fingers.

Check the shutter at one second, and adjust the position of the gear assembly to give a good one second time (a stopwatch should be adequate at this speed). Now check through the rest of the speeds - up to about 1/30 you can pretty much tell by ear how it's doing. If one speed sounds out of sequence, lift off the fascia plate and observe how the levers are lying in the cam slots; one of the levers is probably sticking, which either means it needs cleaning or something is dragging (possibly due to old impact damage). A shutter tester can be used to check speed accuracy at the slower speeds, but the top two will read slow because of the blade travel time. In any case, adjustment options are usually pretty limited and tend to favor the low speed end of the scale. And, unless the shutter has been tampered with, cleaning and lubrication should come pretty close to restoring its original factory adjustment.

Once everything is in adjustment and running well, replace the notched retaining ring. Note that it has a flange extending in one direction at the center hole: this flange goes to the rear. Don't overtighten the ring, it's not intended to exert force on the shutter. Once it's home and nothing is loose, go on to the next available notch and reinstall the small screw (or rotate the flattened disk so that the flat side faces outward). Check the front and rear lens cells to make sure they're clean and reinstall them in the shutter – turn them hand-tight, with just a little less force than it took to remove them.

If you expect the shutter to be used in a cold environment, you may want to chill it to check its cold weather performance: seal the assembly in a zip-lock plastic bag and put it in the refrigerator or freezer, depending on the expected use, for about 15 or 20 minutes, then recheck it (if possible, operate the shutter levers through the bag without opening it). Keep the shutter in a dry place for some time after removing it from refrigeration to make sure any condensation evaporates out of it.

If this was a unit focusing shutter, you're done! If it has a front-cell focusing lens, you still have to reinstall the front cell and refocus the camera.

First, clean the focusing threads well with lighter fluid, both on the lens cell and in the front thread in the shutter assembly (in the second element cell). Apply a thin layer of white grease to the threads. Orient the lens cell just as it was when it released from the threads on disassembly, then turn it counterclockwise a few degrees. Place it against the mating thread and turn it clockwise; if it goes too far without engaging, back up and try again until the thread engages at the proper location (remember that the female part has been unscrewed and replaced, so it could be a few degrees off). Once it's started, turn it in until it won't turn any farther.

The next step is adjusting the focus. For the most part, this method is found in Ed Romney's guide (available at www.edromney.com). It works very well. First, get a piece of glass about the size of a frame of film (probably the ideal is a glass from a slide mount; it needs to be able to rest on the film rails and between the film edge guides). Stick a strip of frosted Scotch tape to one side, and draw a vertical line in the tape with the tip of a sharp knife. Now tape this into the camera's film plane, with the frosted tape toward the lens. Set the shutter on T (or B with a locking cable release), and look in the front of the lens through the viewfinder of a good SLR camera which has a split-image screen; the SLR lens should be the normal lens, focused at infinity. With a bright light behind the repair camera, turn the front cell until the vertical line you cut in the Scotch tape appears straight and unbroken in the SLR viewfinder. Focus is now set at infinity.

Carefully to avoid rotating the front cell, set the lens bezel in place so that it is resting against its infinity stop. Secure it to the front cell with its set screws.

You're now finished and ready to go take some pictures.