hasselblad A12 back problem
I have an A12 back that is exhibiting an overlapping problem, but ONLY on the first frame. I wind the film on, and the first and second frames show an overlap. Subsequent frames do not. The other back I have shows no such problem, so it appears to be caused by the back itself. Any ideas on what this problem would be?
I have the same problem with one of my A12 backs...it works perfectly other than that! I just added it to the pile of stuff to send off for repair...
"Everytime I find a film or paper that I like, they discontinue it." -Paul Strand
Apparently this is a common problem. I found the following at the link http://home.earthlink.net/~blackbird711/manuals.html
"My magazine is overlapping on the first and second frames."
Unfortunately, you have to dish $65+shipping for the solution.
I also found a reference on another popular site about a "clutch" problem causing this issue. I'll update the thread if I find further information.
One of mine had the same problem. I know an excellent repairman who fixed it. He also told me that Hasselblad cameras should be used frequently, otherwise lubricants in the back start to harden which causes these problems.
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When you load the film, try winding it so that the arrow on the film is a little past the mark on the magazine, by 3 or 4 mm or so.
First, has there been a conclusion on what causes this other than 'get the back CLA'd?'
Originally Posted by bdial
What does this winding past the mark accomplish other than position the frames a bit farther down on the film strip? Is there a sensor that interprets this extension?
The answer to the last bit is: no.
Originally Posted by Fred Aspen
It does very little, except move the frames up a bit on the strip of film.
I do that routinely, because the people at my small local lab habitually manage to just fog the bottom bit of the first frame if i don't.
It does not help to prevent overlapping of the first and second frame. I know, because i too had that happen, despite winding the film a bit further when loading.
Fixing it alas is a matter of cleaning, relubing and adjusting the thingy.
After giving this problem some serious thought and doing several dry runs, I have come to the conclusion that the problem is a sync problem between the back and the camera. I will test my hypothesis tomorrow.
Here's what I think: I believe the A12 back and its arrow alignment and crank turns are responsible for the positioning of the first frame. The camera transport is responsible for frames 2 through X, depending on the capacity of the back.
I found in my problematic back that the first frame overlaps the second by what is equivalent to 1/4 turn of the back's crank.
Oddly enough, and I would like observations from other Hassy users, my back's crank turns about another quarter turn beyond the point where the indicator turns white.
Intuitively, I would think the indicator turning white and the crank's mechanical stop should be in sync, the indicator changing just as you hit the stop.
Fellow Hassy users, I would like to know if, on a properly operating back, the white/black indicator turns white at or very nearly the point the crank hits its mechanical stop. Can someone run a quick test for me?
I believe, and I will confirm tomorrow after some feedback, that if I load and turn the back's crank until the indicator turns white and NOT until I hit the stop, the frames will be properly separated.
Alternatively, I believe if I align the start arrow and the back's arrow such that the start arrow precedes the back's orange arrow by a 1/4 turn of the spool and crank into the mechanical stop, I would accomplish the same thing.
I am also thinking that vigorous film loading of the back and coming fast and hard into the mechanical stop may contribute to mechanically changing the position of the hard stop and creating the overlap/sync problem, which, I think, can be avoided by the above 'work around' or having the back CLA'd and the number wheel properly adjusted.
Could someone please verify the operation of a good back and see if the white indicator and mechanical stop are synchronous? This can easily be done with an empty A12 back. I don't want to burn a bunch of film unnecessarily and your contribution will help confirm or deny my hypothesis prior to further testing.
Last edited by Fred Aspen; 06-30-2008 at 06:51 PM. Click to view previous post history.
It's a known problem, fixed by a CLA.
Originally Posted by Fred Aspen
The moment the mechanism stops automatically may need readjusting. And so may the eccentric which is responsible for the distance between first and second frame.
But often it is just a matter of gummed lubricants that keep the thingies from moving freely that cause such problems, and then a clean and relube may be all that is needed.