These pictures can be viewed full size here.
The pictures above show the steps that I took but I’ll also outline the process here.
At the start of this process I had cleaned, lubricated and rebuild the film advance and the Compur-rapid shutter so the parts which needed further work were the focus helicoid and the general linkages and mechanics of the rest of the camera.
The helicoid when I initially received the camera was almost completely solid which is quite common with the karat series. The original grease used seizes up over the years and needs to be removed and replaced with a more modern version. I had the focus unit removed from the camera, so I found the easiest way to remove the old grease was to soak the helicoid with IPA until I could move it and then use lots of cotton buds to remove all the old grease from the threads. I did this by winding the helicoid out of the focus unit as much as I could while keeping the threads engaged and cleaning the threads. I then wound it back the other way and cleaned the threads at the bottom of the helicoid. I did this so I didn’t have to find the correct threads to re-engage as I reassembled the unit. Once I’d done this a few times I added a small amount of new grease onto the now clean threads and worked it into the threads by moving the helicoid back and forth.
When the focus assembly was cleaned and re-greased I fitted it back onto the front of the camera frame, but first I checked the mechanical linkages within the body of the camera, cleaning and lubricating them with a small amount of grease. At this point, with the bellows disconnected it’s possible to do this, and also check the bellow release latch and runners etc.
With the bellows pop-out working nicely I proceeded to refit the shutter unit to the front standard, which I’d re-bolted onto the pop-out and also re-fitted the decorative cover. There is a locating pin on the back of the shutter and a corresponding hole in the helicoid which need to be mated up as the shutter is re-positioned. There may also be a number of paper washers to fit (mine had 3, presumably put on as focus calibration in the factory) which need to be correctly located so the small cut out in the washer fits over the locating pin.
Once the shutter is back in place on the front standard, the locking ring needs to be attached through the back of the camera and tightened up with a lens spanner. With the shutter re-attached, the rear lens element can also be replaced and screwed tight. At this point the focus lever which connects to the rangefinder on the top of the camera needs to be re-coupled to the lens unit which is done by holding the lever on the top of the camera against the spring and feeding the screw through the gap where the bellows would normally extend. This sounds more tricky than it actually is and I found I could get it fitted first time without much trouble.
Now the four screws which hold the bellows in place can also be re-inserted and done up and the majority of the re-assembly is done. At his point I tested that the shutter release correctly worked by advancing the film, cocking the shutter and releasing it.
The next item I dealt with was the door release which got a strip down, clean and re-grease and I also gave the camera cover a clean up with some black saddle soap.
The only major component remaining to re-fit was the rangefinder assembly. As I came to put it back in place I found that the lever on the bottom of the rangefinder which couples to the lever underneath it was sticky. This turned out to just be old grease which was gumming the unit up so I removed the movable component and cleaned and re-greased it. Once it was back together the rangefinder was nicely responsive.
The rangefinder is fitted back to the top of the camera with three bolts which fit through slots allowing the rangefinder to be moved to calibrate it. I found I just needed to set the focus to infinity, refit the rangefinder and put the screws in loosely and then simply look through the rangefinder and move it until the view through the rangefinder showed in-focus at infinity. Then I just tightened the screws.
Finally I refitted the top of the camera and just gave all the basic functionality a run through to check it.
The camera should now be fully functioning and certainly the shutter, film advance etc seem to be like new again, however, I’ll need to run a film through it to be certain.