A few quick things to check:
1) Are the blinds, seen when you remove the lens flat and wrinkle free (this is a quite expensive replacement)
2) Do the slow speeds work properly - wind the camera on and set the main speed dial to 30-1 (change shutter speed always after winding on - no need for film in camera), then gradually reduce the speed on the secondary speed dial on the front of the camera, firing the shutter off and winding on at each slower speed. It is common for the slower speeds to be sluggish but make sure the blinds are not sticking half way across. You should probably factor in having to have a CLA (Clean, Lubricate and Adjust) at around $250 into your thinking, as unless it has been serviced recently, the old lubricant will need cleaning out and replacing with modern non-oxidising/non-drying lubricants.
3) Check for fungus in both rangefinder and viewfinder. This often manifests itself as a ragged appearance around the edge of the RF patch or fogging of the view (more in the VF than RF)
4) Check that the focus lever under the film rewind is focusing the RF image.
5) Check that moving the lens focus is operating the image convergence in the RF. If image convergence is not perfect at infinity (at least 1000 metres away) or vertical convergence is off, don't worry too much as these are both fairly easy adjustments. I find the older Barnack cameras easier to adjust than the modern M's.
6) Use a torch to look down into the slot the film goes into once you take the bottom cover off to make sure there are not torn bits of film in there. This is not uncommon if people have either not been trimming the film leader correctly or using the shiny card method of inserting untrimmed film. Search on the forum for methods of loading film into Barnack cameras.
PS On the lens, the best way to detect fungus is to shine a UV torch or light through the lens (cheap LED UV torches are a few dollars on Amazon). Fungus shows up well with UV light when it can be difficult to see with visible light or light from an incandescent source. W
Edited by wlaidlaw, 12 July 2018 - 16:54.