Kern Switar 50mm f1.8 on Alpa 6C stuck on infinity

[M. Valdemar]

I got a nice Alpa 6C this weekend, and everything is in very nice shape except for the lens.

The lens iris is fine. Glass look beautiful.

The lens is stuck on infinity and cannot be budged. The lens looks mint, everything else on the camera is mint, and I don't think there is any damage.

Is there an infinity lock on this lens? There are some set screws on the back, but I don't want to turn anything unless I know what I'm doing.

I thought it might be rusted, but I don't think so. It feels like something is physically holding the lens at infinity. Is there some lock on this lens?

My lens looks exactly like the one on lower left:

 

[schaubild]

Sounds like the DOF mechanism is stuck. A really complicated piece to take apart if you never had one of them in your hands (and that goes for every camera technician too!). Professional service heavily recommended. There is a guy in New York who has the required tools and knowledge, but I don't know it's name. Use the search funcion.
Or two shops here in Switzerland (Baumgartner/Zurich, Schupbach/Nyon).