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     Winfried Rating: N/A |
From time to time I check the shutter of a camera I just restored. This time it was the turn for a NKS shutter on a japanese MizuhoSix 6x6 folding camera. The shutter is basically an almost true copy of a Prontor II shutter, and these are easy to disassemble, so was this one, and there was no big problem to clean the blades etc. I don't know whether it was due to my mistreatment but the tiny hook which latches the cocking shaft broke off, so I had to disassemble the release levers and solder a new latch. (All this took MUCH longer than writing about it!) Since this camera was designed for 6x4.5 format and has a 'fixed' mask (two hinged blinds) I am planning to use it for slide film and decided to verify the shutter speeds with a phototransistor assembly and a digital storage oscilloscope (Fluke ScopeMeter) to which I have access. It turned out that the slow speeds were quite exact but the high speeds were somewhat to slow - at 1/100 the actual speed just was 1/60 or so, and top speed /1/200 nominal) was around 1/100. I rebent the cam of the cocking shaft which runs against the lever of the escapement gear to speed the shutter up a bit, and now the high speeds are much better although the highest speed (1/200 nominal) still rather is 1/150. When rebending that cam in most cases slow speeds are affected much more, and I had to refile the slow speed cams a bit. So this guy is running fine now at all speeds except for the top speed which is still a bit off and probably will remain that way. More or less for fun I also checked the +70 years old Compur shutter on a 6x4.5 Ikonta. This guy was still running really strong! Most speeds were dead on, except for 1/50 and 1/100 which are approx. 10 p.c. too fast. This one did not reach the top speed (1/300 nom.), too, but the 1/250 it actually has comes pretty close. This shutter did not need any repair, just a few drops of lighter fluid on the speed escapement prior to the test. However I have to say that on most cameras where I cleaned (and sometimes repaired) the shutters I did NOT test the shutter speeds and there was hardly any camera where the first roll of slide film did not turn out satisfactorily. |