hasselblad A12 back problem

dfoo · May 30, 2008

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?

tjaded · May 30, 2008

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...

dfoo · May 30, 2008

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.

dfoo · May 30, 2008

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.

ooze · May 30, 2008

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.

Cheers,
omar

bdial · May 30, 2008

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.

Arvee · Jun 29, 2008

bdial said:
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?'

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?

Fred

Q.G. · Jun 29, 2008

Fred Aspen said:
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.

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.

Arvee · Jun 30, 2008

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.

Thanks!

Fred

Q.G. · Jul 1, 2008

Fred Aspen said:
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. [...]

It's a known problem, fixed by a CLA.

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.

hka · Jul 1, 2008

Fred Aspen said:
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.

Thanks!

Fred

In my case the white indicator and stop are synchronous. But I learned from a CLA that you can count the turns when you spool the film to the first frame. This must be 10 turns and a little bit lets say about 20º. In that last part of the turn the white indicator is coming into the window.
Hope this will help.

Arvee · Jul 1, 2008

Q.G. is correct.

Perverting the loading procedure won't allow me a temporary fix and the proper solution is a CLA. Of course, I can cap the lens on the first shot and reliably shoot 11 properly spaced exposures until a CLA is done.

One back is already in the shop and this one will be following it shortly. It appears that the lubricants have long since hardened.

(I went back to the seller and he indicated that no servicing had been done in nearly 10 years. David Odess recommends servicing the equipment every 2-3 years with normal usage. My problems illustrate his point. Get your gear serviced regularly!)

Thanks all.

Fred

edtbjon · Jul 1, 2008

Yes, Hasselblad needs CLA now and then to be a happy camera. Now, if you collect all the bits and pieces that will need the attention of the camera magician of your choice, I'm quite sure that a quote for all of your gear will be much better than a quote for each and every single piece.
E.g. I had some 5 items (a stuck shutter on a C lens, an A12 mag, three LF shutters), which all were repaired/CLA'd for less than the CLA cost for two times one LF shutter. The C lens was maybe worth $100 before the CLA (as it didn't work) and $350 after. I.e. selling the C lens after repair paid for the repair and CLA of all the items.

//Björn

Wayno · Jul 3, 2008

I also had a back with this problem and opened it up to have a look. The adjustment is via the three locking screws visible on the counter wheel in the attached picture. This was some time ago, but I seem to remember that a locking pawl (just visible near the "1" I think) falls into the cutout visible near the "7" to stop at the first frame. This needs to happen at exactly the same time as another pawl reaches the first frame position on the wheel which has cutouts for each exposure (sorry, I don't know the proper names). Anyhoo, if these two are out of synch, the first frame may overlap the second.

Gary Holliday · Jul 3, 2008

Hi wayno and welcome to the forum. So what adjustment should be made to the counter wheel. Loosen the three screws and re-align? Is it something a mortal can attempt?

Wayno · Jul 3, 2008

Thanks Gary.

Yep, loosen screws and turn the wheel to the right position, then tighten. The other wheel with the cutouts for each exposure is on the same shaft but underneath the counter wheel (as I recall - this is streching the memory). A pretty easy fix really. I contacted David Odess to confirm that I was on the right track before I made the adjustment. He was kind enough to reply and confirm that I had the right idea.

You can feed a sacrificial roll through the back and mark the position of the first two exposures with a pencil to check the spacing. This is a bit tedious with all of the interlocks, removing the darkslide, etc, but worth it to know that you've got the adjustment correct.

A note of caution - if you remove the black frame that's on top of all of the gears then things can go SPROING! Don't ask me how I know... although I did get it all back together.

Arvee · Jul 3, 2008

Wayno,

Thanks for the input and the photo. How about some general information on how to gain access? I am looking at the back and don't see a way in except for removing the screws on the frame surrounding the dark slide. Is this the proper route?

I've got the later version, A12-6x6, with the dark slide storage feature on the rear of the back.

-Fred

Wayno · Jul 3, 2008

You have to peel off the leatherette covering on the end with the wind crank. The screws are underneath.

Arvee · Jul 3, 2008

Thanks, I have it disassembled to that point and will remove the leatherette.
Will post results.

Thanks again!

-Fred

Arvee · Jul 3, 2008

Wayno,

That was pretty simple to repair. Thanks for the help.

-Fred

hka · Jul 4, 2008

Some backs have a wider space between the negs than others how is that be done or possible?
Any thoughts?

Arvee · Jul 4, 2008

Not sure this is the reason but in all my monkeying around with the a12 back, I was marking the frames of a sacrificial roll and found that the transport doesn't always keep the film as tight as I would like it to be. I think the variation in 'looseness' in the supply spool is responsible for the variation in the spacing between frames. There is a small brake, a spring loaded 'pillar,' on the supply spool that may be weak in some backs an allow some slop in the unwinding process.

Just my .02,

-Fred

hasselblad A12 back problem

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