Operations carried out
Cameras and lenses
Leica IIIc - 1946
This Leica mainly had a rangefinder problem, the focus image was invisible.
After disassembly, the speed control determined that they were wrong and that the 1/1000 did not even allow an exposure.
A CLA was essential.
The procedure :
Removing the cover – Removing the body and the film press – Removing the front plate – Removing the bottom plate – Removing the slow speed mechanism – Cleaning and lubricating the slow speed mechanism – Checking the high speeds – General lubrication – Adjusting the tension of the curtains – Adjustment of rapid speeds – Disassembly of the defective mirror and replacement – Partial reassembly – Adjustment of the rangefinder – External cleaning and reassembly.
Removing the hood
Dismantling the arming button, 1 screw on the side to loosen
Removing the spool pin, counter and central crown
Dismantling the flash shoe, 4 screws
Disassembly of the release lever, 1 screw and 1 small washer
Rewind button disassembly, 1 screw
Removing the U-shaped rewind drive part
Dismantling the rangefinder diopter selector, a ring to unscrew
Disassembly at the rear of the eyepiece protection, 2 screws
ATTENTION !! The two small lenses must be held with a small piece of tape immediately after removing the protection.
Disassembly at the front of the two finishing rings of the viewfinder and the rangefinder
Removing the vertical adjustment, it is not screwed, you have to lift it and unscrew the support
Unscrewing the front viewfinder lens
Unscrewing the 5 chrome screws that secure the cover to the main body
IMPORTANT !! The cover is blocked by the rectangular viewfinder lens in the center of the rangefinder, you must carefully move the bottom of the cover to release and remove it
At this point, the rangefinder, speed selector and shutter mechanism are visible
Dismantling the body and faceplate
Removing the body is easy, as there are only the two front screws left to remove.
Removal is done by pulling the mechanical blocks upwards.
The film press and the two pressure springs are released. This film press has an inclined side, which must be placed downwards when reassembling because it helps the passage of the film.
Dismantling the front plate begins with removing the 3 screws that hold the thin black sheet metal plates isolating the chamber from the lens mount support.
When reassembling, never force these screws, the sheet metal is thin.
Then, you must remove the 4 screws securing this plate.
ATTENTION ! There are 3 flat head screws and 1 countersunk head screw which is next to the slow speed selector.
Principle of slow speeds and lubrication
The operation of slow speeds is broken down into several phases.
1/ Selection of the minimum operating speed 1/30
2/ Selection of slow speed (example 1 second) on the button on the front.
3/ The first action of selecting a slow speed is to modify the position of the arm located behind the front plate in order to put the slow speed mechanism in the active position.
At speeds 1/30 and faster, this arm disengages the mechanism so as not to slow down the shutter.
3/ The rotating cam placed behind the button modifies the pressure on the shaft which supports, at the top, the slowing down cam of the second curtain, at the bottom, the “fork” which is driven by the slow speed mechanism.
At speeds 1/30 and faster, the slowdown cam is positioned away from the shutter and cannot slow down the second curtain.
4/ When pressing the trigger, the shaft lowers in order to position the deceleration cam at the level of the rotating cam of the second curtain (located under the gear selector).
5/ The first curtain opens, the second curtain is slightly released.
6/ The slow speed mechanism is engaged, the cam at the top holds the second curtain during the delay of the slow speed clock mechanism.
7/ The selected time (1 second) expires mechanically.
8/ The second curtain is finally released, which completes the shuttering.
The slow speed mechanism is held in place by two screws.
When it is removed, it must be cleaned by bathing it for a few minutes in isopropyl alcohol and drying thoroughly.
Lubrication with fine oil is only done on the pinion bearings, never on the mechanisms.
General lubrication
The first step is to do a little internal cleaning before lubrication.
On screw-type Leicas, lubrication is relatively basic, you only need fine oil, fluid grease for the lower gears, and a little more solid for the cocking gears.
The difference in grease is important, because the lower pinions, although related to those of the armament, must in no case be slowed down or slowed down by grease that is too firm or sticky.
These low pinions are those which ensure the rotation of the second curtain drum during shuttering.
The high pinions ensure the advance of the film and the tensioning of the shutter, they have no influence on the shutter when triggered.
The lubrication of these pinions must be carried out with a grease which gives flexibility and softness to the entire armament.
IMPORTANT !! Lubrication must be done without excess, a mini drop of oil and a thin film of grease is more than sufficient for reliable operation for decades.
Any overflows are removed with isopropyl alcohol on cotton swabs.
Green arrow = Fine oil
Yellow Arrow = Low viscosity grease
Blue arrow = Normal viscosity grease
Quick speed controls and adjustments
To check and adjust the curtains and speeds, you must temporarily reassemble the arming button and the speed button, taking care to place the spring of the anti-return cam on the top of the coil support reception of the film.
You can read the description about basic curtain tension on this page: CURTAIN TENSION
The tension adjustments are made on the two adjustment screws on the bottom. The adjustment of the first curtain is towards the rear, the second curtain towards the front.
Depending on the direction of rotation, the tension will be increased or reduced.
This action allows you to adjust not the shutter speed, but the scrolling time of each curtain in front of the exposure window. This notion may seem abstract, but it is logical.
A little essential theory
I remind you for the record that the shutter speed is the space between the two curtains, when passing in front of the exposure window.
This space is different depending on the selected shutter speed. 1mm for 1/1000, 2mm for 1/500, 4mm for 1/250, etc etc.
From this observation, it is logical that this space remains identical from the beginning to the end of the film exhibition.
To obtain this result, the scrolling (or movement) time of each curtain must be as identical as possible.
If these settings are defective, for example, the second curtain is too fast, it will join the first before the end of the exposure and the negative will have a transparent band (black on a positive) because this part will not be exposed…
In practice…
It is necessary to compromise on the choice of the standardized speed selected to adjust the scrolling speed of the curtains.
Generally, this is the flash sync speed, because it is the speed at which the first curtain has completely uncovered the exposure window and the second has not yet started closing, this is what allows the flash of the flash to expose the entire negative (logical isn’t it!!!!)
On this device, there is no sync-flash. The choice therefore falls on the average speeds of 1/60 or 1/100.
A reliable shutter tester is essential. As this article is aimed at amateurs or beginners in repairs, I used an amateur tester with three measuring diodes, the Shutter Lover.
This control tool has the advantage of being autonomous, it does not require additional flashlights. It allows measurements to be read either on its small screen or using dedicated software which allows the information to be read and stored on a computer.
It is precise, and allows adjustments to be made simply.
On this Leica, the 1/500 and 1/1000 settings are independent by adjusting two eccentric screws located on the “latch”.
You should therefore not adjust the shutter to these two speeds, but adjust them last without changing the curtain settings.
Under no circumstances should the armament be rigid or too firm.
If so, the curtains are too tight.
This table shows:
1/ The running times of each curtain and the speeds obtained before intervention.
2/ The running times of each curtain and the speeds obtained after lubrication.
3/ The running times of each curtain and the speeds obtained after adjustment.
Old or used mechanical shutters always give irregular results, even with the most precise adjustments possible.
The speeds engraved on the button are standardized, but never correspond to the actual speeds of a shutter.
This has no influence on the negatives as long as these deviations remain within the manufacturer’s tolerance.
This tolerance can range from 10 to 30%. Note that 30% corresponds to 1/3 of the exposure value, which is derisory.
Removing the faulty mirror and replacing it
Aging rangefinders lose contract and readability.
In 90% of cases, the semi-transparent mirror positioned at 45° which transmits the image from the rangefinder to the center of the viewfinder has lost its transmission quality.
Cleaning the viewfinder:
Disassembly of the upper plate, 3 screws.
Removing the pressure spring.
Removing the prism and viewfinder frame.
Clean with a soft cloth, this part is rarely soiled.
Reassembly.
Mirror replacement:
On the rewind side of the rangefinder, a cover must be removed.
The defective mirror can be removed by simple prying or peeling off with very little solvent.
The supports must be gently cleaned of old glue.
Before placing the new mirror, it is preferable to reassemble the body with the lens mount, which allows you to be in a real focusing situation, with an optic fixed to infinity.
The new mirror (imported from Japan) has a bluish side and a yellow side. The yellow side is positioned forward.
Gluing (Pliobon glue) must be very sparing on the top and bottom supports. Logically, the collage on these supports corresponds to the original positioning.
Temporarily reassembling the rangefinder lens allows a temporary adjustment of the height and to verify that after the glue has dried, the height and width (to infinity) adjustments of the rangefinder will be without difficulty.
The photo of the rangefinder sight (on the smartphone ;)) was taken with the optics on infinity and the subject at a very short distance to mark the visibility of the rangefinder.
Final reassembly
Logically, reassembly is carried out in the opposite way to disassembly, after external cleaning of various parts.
Before replacing the top cover, you must ensure that the clutch is not in the partial or total film rewinding position. The movable cam must not be placed under the latch. If this were the case, after reassembling the cover and cocking, the shutter would not function normally.
Taking photos at each stage, before and after dismantling is very useful, even essential, it is a precious help. (70 images for this intervention).
Each disassembled part must be stored in order in compartmentalized boxes, this also helps with reassembly and avoids misplacing parts or screws.
LEICA the legendary brand
I decline all responsibility if you damage your toys!!! There are also professionals to do this work!
