Disassembly - Voigtlander 75mm F1.9 Ultron SC Leica M mount lens

 In this article I'm accessing aperture chamber of Voigtlander 75mm F1.9 Ultron SC Leica M mount lens to clean dust particle migrated there. 

It's one of the newest 75mm Leica M mount lenses Cosina crafted with extended close focusing down to 0.5m and there little to no details online how to open it. Lens is impressively lightweight and compact, though is very durable and has modern image rendering. You may be interested to also check the article on disassembly of Voigtlander 75mm F1.5 Nokton performed two years ago.

Disassembly steps

Voigtlander 75mm F1.9 Ultron SC disassembly is starting from the mount area. First use flat screwdriver to unscrew four bolts and remove mount ring.

It will open more convenient access to three black bolts marked with arrows, they are holding RF couple cylinder and set of calibrating sims under it. Bolts are strongly glued and require extreme care unscrewing them by applying pressure toward bolt head and creating initial torque using pliers grabbing screwdriver.

Note - memorize radial position of RF couple cylinder - it has precisely curved edge area which should be located at same side near DOF scale during assembly.

Once RF couple cylinder is detached it is possible to see the wide retention ring connecting optical core frame with focusing frame. Ring has two rectangular detents and many people would use spanner wrench to unscrew the ring CCW.

Though I'm using safer approach, similar to Voigtlander 35mm F1.4 disassembly. I'm adding thin layer of adhesive foam to the edge of plastic cylinder made from pills container, diameter is around 32mm. Then I'm attaching cylinder edges to retention ring with firm press and rotating it CCW.

After unscrewing and extracting retention ring, focusing frame and optical core frame can be disconnected. Red arrow are indicating silver pin and rectangular groove that need to fit during assembly. Green arrow is pointing at the set of infinity focus calibrating shim rings.

Next step is to wrap soft rubber band around rear optical module frame in pointed area and accurately unscrew it CCW.

Once rear optical module is detached there is access to the aperture chamber. I'm using air Rocket Blower to get rid of dust particle at the inner glass surface.

Then I'm assembling lens back in a reverse steps order.

Note - the front nameplate can be unscrewed in a CCW direction following front filter thread. It will expose access to three bolts which I initially assumed would hold the front optical frame. Though actually that bolts are holding metal frame that is encapsulating only few front glass elements, so removing it will not open access to aperture chamber yet.

Conclusions

Voigtlander 75mm F1.9 Ultron SC is relatively easy to service by first separating optical core frame from focusing frame. Thick aluminum parts look durable and also very thick brass parts are used for focusing/RF helicoid guiders which explains silky smooth focusing operation even when mounted on M camera. It's great to see that lens has easily tunable precision of RF cylinder and precision of infinity focusing by configuring thickness of shim rings set.

Focusing helicoid

Below are few pictures of focusing helicoid frame with mount ring and front area of focus ring removed. The range of extraction is impressive. The focusing scale ring is made of solid brass, as well as four massive helicoid guiders.