Leica IIIC Beam Split mirror R&R

[_goodtimez]

Hi,

I received the new 50/50 beam split mirror and I proceeded to a replacement test on my old IIIC. The RF image was pretty dim and I figured that I wanted to DIY this operation.
No major problem but the horizontal RF adjusment screw was a little hard to turn. A drop of synthetic oil unfreezed it for good and allowed plenty of travel for the final adjustment.
Here are some pics:


Leica IIIC Beam split mirror R&R by CustomM8, on Flickr


Leica IIIC Beam split mirror R&R by CustomM8, on Flickr


Leica IIIC Beam split mirror R&R by CustomM8, on Flickr

More photographs in this set :

http://www.flickr.com/photos/8487951@N05/sets/72157625135357333/

 

[John Shriver]

That's an odd arrangement for the mirror. From my IIIa, and from what I read about the IIIc, it is normally held in place by a spring-loaded wedge. But yours looks as though the mirror has been glued in place. Maybe some previous tinkerer lost the outer wedge, and glued the mirror in place to deal with the problem.

The fixed wedge you show removed normally never has to come out of the rangefinder.

So long as the mirror is at the proper 45 degree angle, and you can get the right vertical alignment, you should be OK.

 

[_goodtimez]

Hi John,

That is the original arrangement on the IIIC. There was an issue with the H adjustment because the new mirror is thiner than the OEM and thus the reflective plan is a bit closer to the prism. The H adjustment screw had a limited travel (because of small corrosion) at first and I only was able to rotate it 1 turn. After I realized it and finally got the full travel it became OK.
The V adjustment is initially performed by tilting the mirror brass housing. If you look closly, the LH single screw is tapered and the 2 RH screws have a bevel. With this you can actually rock the housing in position and at the end obtain a good V adjustment before you re-install the frontal optical element.
My other IIF camera RF now looks very fade in compare and I am going to do it this afternoon.
I just want to add that cutting the glass was easier than I thought. I made a gross cut at first using pliers and got the final shaping using a normal stone grinding wheel machine. I simply used masking tape on the jaws of the pliers to avoid scuffing the glass.

 

[John Shriver]

Interesting that they changed the design on the IIIc. On the IIIa, the silvered side of the mirror is towards the rear eyepiece, so the thickness of the mirror becomes irrelevant. That might not have worked well if that's the cemented side.

No question what a huge improvement a new mirror can make. The old silvered ones weren't very stable. My current one (a Leica part, ordered from a Japanese eBay seller) is aluminized, should last a long time.

 

[Rachgoodtime]

Well done !

 

[kpas]

That's an odd arrangement for the mirror. From my IIIa, and from what I read about the IIIc, it is normally held in place by a spring-loaded wedge. But yours looks as though the mirror has been glued in place. Maybe some previous tinkerer lost the outer wedge, and glued the mirror in place to deal with the problem.

The fixed wedge you show removed normally never has to come out of the rangefinder.

So long as the mirror is at the proper 45 degree angle, and you can get the right vertical alignment, you should be OK.

Interesting you say this. A IIIc I was working on today has a similar setup where the mirror is merely held in the wedge by friction. I replaced the mirror and had to use a small spot of glue to get it to stay put.

Having an issue now that the RF patch is out vertically and I cannot figure out for the life of me how to adjust it.

Can anyone offer me some suggestions?

cheers

 

[xayraa33]

Interesting you say this. A IIIc I was working on today has a similar setup where the mirror is merely held in the wedge by friction. I replaced the mirror and had to use a small spot of glue to get it to stay put.

Having an issue now that the RF patch is out vertically and I cannot figure out for the life of me how to adjust it.

Can anyone offer me some suggestions?

cheers

Have you rotated the RF prism window ( the one closest to the shutter speed dial) to align the vertical RF image properly?