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Beam splitter mirror replacement in Barnacks and clones

[From the Archives, ca. 2005]



Replacing beam splitter mirrors on Barnacks and clones
is relatively easy....


Leica II beam splitter mirror


Tools


Compressed air, lens cleaner [or windex], spanner wrench, jeweller's screwdriver [1.4mm and 2.5mm], ring wrench [micro-tools 50D] sharpening stone, glass cutter, tweezers, air blower, lens tissues, cotton swabs and needle nose pliers. A digital camera may come in handy too.


To the left is a mirror type beam splitter from Edmund Scientific catalog no. 3043359 with 50/50 reflectivity/transmission. This size is good enough to service a number of Barnacks and clones. To the right are two corroded samples of 8 mm x 10 mm beam splitters taken out a Leica II and Fed 1d. The one at the bottom is a replacement I carved out from the larger mirror. I used a cheap glass cutter from Home Depot and the cuts where not clean so I had to shave it down to size with a sharpening stone with flowing water in the kitchen. I would welcome glass cutting tips from people who have experience working with glass.


To remove the rangefinder cover or top plate set the shutter speed dial to Z [or B] or any speed to gain convenient access to the set screw. It may be wise to write it down for reference in reassembly. If the dial only has one set screw chances are it is threaded [Leica, Feds and earlier Zorkis]. Loosen the set screw and turn the dial counter clockwise for removal. On later Zorkis like a 1d the dial is not threaded and will come off once the the two set screws are loosened.

The next step is to remove the three screws securing the accessory shoe and lift it off.


Then remove the screw covering the infinity adjustment [right beside the VF bezel].

Using the ring wrench from micro tools, remove the bezel around the optical wedge and also the RF window. Then using a spanner wrench or needle nose pliers, carefully turn the optical wedge counter clockwise to remove it.



Turn the camera around and remove the screw in between the RF and VF eyepieces and using the ring wrench remove the eyepieces. Carefully remove the RF cover making sure it does not scratch against the rewind knob.

If you encounter difficulty in removing the bezels, optical wedge and RF/VF eyepieces try dropping tiny amounts of thin oil [watch maker's or Radio Shack 64-2301] or even lighter fluid and let it sit for a couple of hours.

Two links with better illustrations on how to dismantle a Barnack clone:

Zorki 1d with the RF cover off. The eyepiece tunnels on this late Zorki is one piece and detachable, soldered on most Feds and threaded in Leicas. For proper reassembly take note of the difference between RF and VF eyepieces since they have similar threads, the RF is 1:1 and you can "see through it", while the VF is convex and will be blurred.


Pry off the cover on the side of the beam splitter mirror with a small screw driver.


You will find a "leaf spring" securing the beam splitter mirror wedge. Pry this off very carefully with tweezers and/or a screwdriver because it can fly off.


Front

Now is a good time to clean and dust away dirt from the RF/VF housing using lens tissues and cotton swabs moistened with lens cleaner or windex. Use compressed air to accelerate drying.
You will also notice in this picture that there is a single screw cover directly above the infinity adjustment worm screw. If you encounter difficulty in turning the infinity adjust, remove the cover and loosen the set screw inside for the worm screw to turn freely. Many infinity screw heads have been stripped due to tight adjustment.


Back


The wedge came out fully in this Fed 1d however on other models, it may not be possible for the wedge to slide out completely if the tip of the screw that holds the RF housing is in the way. In this case you have to carefully shake out or maneuver the wedge with tweezers to slide out or install the beam splitter mirror.
In this picture I just inserted a new mirror and is ready for reassembly. Take note of the assembly sequence - wedge, leaf spring and cover.

Reassembly is done in reverse order.

Before you use the camera you need to recalibrate the vertical and horizontal RF adjustment, if you need information on this procedure go to Jay's Fed/Zorki survival site.


If contrast between moving and stationary image is an issue you can try cutting a small piece out of an enlarger contrast filter just big enough to be wedged in the RF tunnel when the RF eyepiece is screwed back on.

Leica IIIc and IIIf

Good luck and good light!

Comments

  1. What size is the wring wrench you use here?

    ReplyDelete
  2. In terms of contract issue, I cut one piece of old color film, and put back as above mentioned. It works very well.

    ReplyDelete
  3. Just wondering, is there any collimating for infinity focusing to be done after this is completed? I used this pictorial for a Leica II a few years back and it worked fine without collimating but I have another Leica II that needs a beam splitter replacement and now wonder if I simply was lucky last time!

    ReplyDelete
    Replies
    1. Hi Johann,

      I've done it on my Leica II + a couple Fed/Zorki 1s and have never had any collimating issues. After installing a new half-mirror, just adjust the RF the normal way.

      Good light!

      JE

      Delete

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