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George
Tinkerer
Username: George
Post Number: 5
Registered: 12-2012
Rating: N/A
Votes: 0 (Vote!) | | Posted on Saturday, April 06, 2013 - 05:09 pm: | 
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I have a 1968 hasselblad back, serial number TR124xxx.
When I acquired it it was not working. The back was winding, but failing to advance the counter or stop at frame 1.
I have dismantled it and reassembled it. Someone else seems to have had a go before, gave up and reassembled it incorrectly.
It appears the problem is caused by a faulty wind/rewind knob. When I rest the mechanism manually from inside it all works fine.
However, when I go to turn the film advance knob in a counter clockwise direction it just turns and does not engage the reset trigger! It works fine and but pushing a lever from inside, I can get the counter to reset.
Are there any parts missing in the wind mechanism?
Attached is a photo. |
George
Tinkerer
Username: George
Post Number: 6
Registered: 12-2012
Rating: N/A
Votes: 0 (Vote!) | | Posted on Saturday, April 06, 2013 - 05:12 pm: |
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here is the photo |
Brcamera
Tinkerer
Username: Brcamera
Post Number: 262
Registered: 08-2010
Rating: N/A
Votes: 0 (Vote!) | | Posted on Saturday, April 06, 2013 - 07:27 pm: |
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The parts you show in the photo simply advance the mechanism via the pawl, or reset it by turning the inner shaft counterclockwise. Pretty basic and other than the screw that holds the pawl assembly in place, all the parts are accounted for in the photo. If you have the pawl assembly keyed on to the inner knob and it still does not reset, then there is some issue under the mechanism plate.
By the way, the title says A12 back, but you do not have an A(automatic)12 back, shown is the early 12 back.
Bill |
George
Tinkerer
Username: George
Post Number: 7
Registered: 12-2012
Rating: N/A
Votes: 0 (Vote!) | | Posted on Sunday, April 07, 2013 - 03:44 am: |
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Hi Bill, Thanks for your reply.
The parts in the photo, when fitted, do not actually turn the inner shaft counter clockwise.
When you turn counter clockwise you can see and feel that the pawl mechanism underneath the knob clicking, and not apply any force to try and rotate the inner shaft.
At this stage I am not convinced that the inner shaft is ceased. The knob seems to just spin.
Clockwise it works fine. The pawl engages and the inner shaft is rotated.
George |
Brcamera
Tinkerer
Username: Brcamera
Post Number: 263
Registered: 08-2010
Rating: N/A
Votes: 0 (Vote!) | | Posted on Sunday, April 07, 2013 - 02:03 pm: |
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George,
The inner shaft, which is keyed to the winding knob, has two functions: it provides a support for the winding knob and when turned counter clockwise, activates the mechanism to return the counter to zero. When the winding knob is turned counterclockwise, the pawl is disengaged and does not function in any way with the inner shaft. Movement of the shaft is provided only by the turning of the winding knob which is screwed on to the shaft-a direct connection..
Bill |
George
Tinkerer
Username: George
Post Number: 8
Registered: 12-2012
Rating: N/A
Votes: 0 (Vote!) | | Posted on Sunday, April 07, 2013 - 04:04 pm: |
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Ahhhhhhhhhhhh!!! Yes, of course that makes perfect sense.
It appears that the cog has been slipping on the metal central shaft and actually stuck in the brass bush. When I look carefully I can see a hair line fracture.
So, either I need to fix the cog to the shaft. Maybe a little super glue or epoxy might work?
Or get a new replacement center mechanism.
I will call Hasselblad tomorrow, though have little hope that they will have a part or that it will be inexpensive enough to be worth bothering with. |
Brcamera
Tinkerer
Username: Brcamera
Post Number: 264
Registered: 08-2010
Rating: N/A
Votes: 0 (Vote!) | | Posted on Sunday, April 07, 2013 - 08:16 pm: |
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I would be very surprised if Hasselblad has parts for a 12 exposure back that was discontinued 45 years ago! If they don't, send me a photo of the part you need and I may be able to help as I have quite a good stock of Hasselblad parts.
Bill |
