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The Ikonta Korner
Synchro Compur MX

Having picked up yet another Zeiss folder only this one has the classic Synchro Compur MX shutter. I'll dispense with the removal of the shutter from the camera body as it is similar to previously mentioned procedures.


Here is a nice example of a  Synchro Compur MX shutter from a Zeiss Ikonta 524/16, made between 1956 and 1960. We are going to do a full cleaning, and where possible, adjustments. This shutter has the booster spring for the 1/500 speed setting. This is a rather complex shutter with many interdependent assemblies that need to work smoothly for correct operation. Ready?

Set the focus to infinity and loosen the three set screws around the focus scale bezel to remove.


Before you do anything else, make a reference mark to align the helical to infinity. I just used a marker to make a line that is at the 12 o'clock position. I've also taken a quick measurement to reference the gap between the front lens and shutter base for assistance when re-assembling.


Now you may unthread the lens helical making note of exactly when the front lens releases from the helical. This will be your insertion point back into the helical come time to re-assemble.


OK, now you can remove the lens and set aside in a safe place.


Make another reference mark to align the inner lens assembly with the locator pin. This too will aid in aligning at time of assembly. This inner lens with the helical can now be unthreaded for removal.


This cam will need to be rotated to clear the inner race which will then allow the base plate to rotate counter-clockwise about 30 degrees to remove.


Underneath the base plate is the speed cam selector revealed.


First we'll glance at the operation of the speed selector cam and how it actuates things. Our first goal is to gain access to the shutter speed regulator or escapement mechanism.


First step in going inside is to lift off the speed selector cam which will give us access to remove this shutter cocking lever.


To remove the shutter cocking lever, this coil spring must be disconnected from the post shown at the tip of the tweezers.


It may be better to make a little elbow room. To do this we must disconnect this spring by swinging the end clear of the groove that holds it. See arrow.


Now just lift the shutter cocking lever complete with spring dangling on the end. See the shutter escapement mechanism shown by Red Arrow. That sucker is next...


But first, disconnect the delay spring from it's post.


Here's the reverse angle showing the same spring.


The spring will just come away and probably by surprise, where upon you will be asking yourself, "Just where did this thing connect to?" Not to worry, we'll have a close look at this come time to reassemble.


Remove this screw on the one end of the escapement mechanism. There will be a spring on this screw which should come along for the ride.


A little ingenuity and a Dremel grinding tool is needed next to form a tool. I keep old worn out blades from a hobby scalpel. They make for good material to make special little tools such as the one we need.


Here's our tool in service. Note the screw and spring from the previous step at the right.


And here is the escapement mechanism ready to be cleaned by submerging in solvent. End of goal #1, perhaps a good time for a beer.


The shutter actuator lever is next. Disengage the small spring.


And lift away the lever.


This allows access to the delay mechanism. Remove this screw first.


Then loosen the screw at the other end that also holds on the MX selector.


Remove the MX selector with the screw making note of the spring that rides against it.


Place this spring with the MX selector.


Disconnect this spring.


Lift off this assembly taking note of the following, two spacers shown by Yellow Arrows and clutch item shown Red Arrow



Delay arm actuator next.


Let's have a look at the delay escapement before we disturb things.


Remove the escapement to end this step. See how nice and empty the compartment is? If you are not brave enough to mess with the shutter leaves, then maybe this is where you stop and do some cleaning and reassembly. For those who know no fear or those voyeurs who "like to watch", proceed onward.


Loosen off this screw that holds the flash hot sync. No need to remove it as just loose is good enough.


Flip the whole assembly over and remove these 3 screws


Read ahead for the next couple frames to see what trouble you are going to get yourself into. Very, and I mean VERY, carefully lift off the back.


Watch out for the flash hot sync that it does not bind up while attempting to remove the back. That was why you loosened the screw that holds it down. It should be free enough so that it will lessen any possibility to bind. Even though, keep an eye on this.


If you've lived your life right, have good karma, helped an occasional old lady across the street and believe in the Easter Bunny, you'll be able to lift off the back revealing the undisturbed blades of the shutter sitting there nicely.


Here's the sequence order to removing the individual shutter blades.


Going further, to access the ring actuator, remove the 4 screws holding the base plate, making note of the size differences of the screws.


Lifting off the plate will reveal the ring actuator. Now you may clean the ring actuator and the surfaces it slides against.


Carefully clean each shutter leaf. Some people even polish each leaf to give a smooth friction free action. There may be some basis to this crazy assumption. I'll try it on my next project.


If the aperture is oily or otherwise sticky then you may elect to just immerse the whole assembly in solvent to clean. Probably the easiest method for sure but being that this is a slavish devotion to our labour, we go that extra step that sane people elect not.

Remove the 4 screws as indicated...


Take a good old sink stopper and place it as shown in the following to support the aperture leaf base plate.


See, just like that...


Holding the assembly together with the 4 screws removed, invert the whole unit and carefully lift off the shutter casing.


Here's what you will have, only under the most extreme cases should you mess with these little buggers. Even I'm not that crazy as to touch the aperture blades. Our goal is to clean the the shutter casing and lubricate the surfaces that the aperture and shutter ring actuators ride on, not give ourselves a big headache.


Remove these two screws to remove the last bits of the aperture actuator.


You may now clean the shutter case and start the reverse process of assembling. Lubricate sparingly the surface that the aperture ring slides on with grease.


Likewise, apply a bit of grease on the adjoining aperture ring, step backwards through the procedure to re-apply the actuator into the shutter casing and the casing back onto the aperture blades. Check it out, smooth huh?


Further, here's another trick to help with assembling the shutter blades, using something to support the blades in the center like indicated otherwise they have a tendency to fall making for a frustrating day. Using any round item you have, be it a cut down broom stick, old wine bottle cork, rubber stopper, or as I have a round cylinder of steel, place it under the shutter assembly to create a flat surface through the opening of the shutter.


Step through and re-apply each shutter blade in the reverse sequence shown previously.


Carefully cap off the shutter by re-applying the casing over the shutter blade assembly. When placing the top aperture half of the shutter back on to the other half, be VERY careful not to disturb the gently sitting leaf blades.


Pay attention to the next bit of detail, you probably didn't notice things when you took the delay clutch out. Notice that there little spring. Yup, that one...


Invert the main part and apply the clutch. Never mind the spring just yet.


Go to Radio Shack or where ever and get one of these little clamps. It's going to make life so much easier for the next steps



Flip 'er over and take that spring and...


Place it in the groove on the part of the clutch that extends up.


You should be able now to remove the clamp and the spring pressure will hold it together with just enough force where you can place it into the shutter.


When you place the delay clutch back in, the clutch arm teeth should engage the gear, Red Arrow, with the cam lobe positioned in relation to the flash trip arm at Blue Arrow.


When placing this assembly back in place, try not to disturb the relationship of the flash trip arm and the cam lobe, as indicated by Red Arrow.


The whole escapement mechanism can be cleaned using what ever method or substance at your disposal, just make sure no residue is left behind. from the solvent used and if you are some sort of "keener", and frankly who isn't, you may lubricate the shafts of the escapement mechanism with an approved light oil.


Just a word on said light oil. I use a synthetic arctic grade instrumentation oil made by Moebius, Arctic 9040. I have a friend who is diabetic and he is a great source for hypodermic needles when I need them for precise oil applicators. I leave it to you for alternate sources of hypo needles.

When hooking up the delay spring shown in first of above two images, aim for the hole indicated by the Yellow Arrow in the second image.


After getting the escapement back in place and the delay spring, make sure to place the following springs in their proper locations.


A few adjustments are required when the escapement mechanism is installed. First only just snug up the screws to allow some adjustment of position. At this spot some clearance is required so to ensure bind free operation. Use anything handy to get about .3-.4mm (.012-.016") clearance. Remember your old feeler gauges from when you used to do service to your own auto, now's a good time to put them back into service. When satisfied, tighten the screw at this end of the escapement somewhat more to only allow position adjustments to happen at the other end.


Adjust the position of the escapement mechanism at the end indicated to affect shutter speed fine tuning. See below for that...


Using a photo-transistor detector we can measure our shutter speed with simply a flashlight as a source.


Just a word regarding effective shutter speed. All leaf type shutters exhibit a time duration delay while opening and closing that is different depending upon the aperture opening. As the shutter begins to open a small amount of light is entering and hitting the film. This is expressed by time duration 'x' on the waveform. Assume the aperture is set to the largest setting, the shutter continues to open allowing in a greater amount of light. When the shutter has fully opened there is a consistent amount of light hitting the film. The shutter stays opened for a predetermined amount of time as set by the shutter speed, then starts to close. This is expressed by time duration 'y' which is somewhat different from time duration 'x'. Since the shutter cannot instantly open and close, there will always be a duration lag while the shutter actuates.

So how does one actually measure a leaf type shutter which when depending on the aperture selected you may have a different time duration? Consider that most of the time we use an aperture of f8 or f11, one could set the measurement point, or if using a photo detector the sensitivity trigger, at the desired f8 opening point as expressed by time duration 'n'.

As recorded by the photo detector we can see that the duration of the time that the shutter is in the state of either opening or shutting is a significant portion of the total elapsed event. It is most profound at the very fastest of shutter speeds and less of a concern at slower speeds. Here we see a measured opening duration of 328 uSeconds and at a setting of f11 we find the total exposure time of 2.33 seconds for the fastest setting of 1/500, this is pretty damn good.


This is a very complex shutter mechanism and if you had everything work out right while working through this you'll have an exceptionally nice camera to show for your efforts.

January 01, 2008