Mamiya 645 lost spring

Discussion in 'Medium Format Cameras and Accessories' started by darxmurf, Aug 20, 2014.

  1. darxmurf

    darxmurf Member

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    Hi all,

    Yesterday my mamiya 645 Pro decided to stop it's mirror in middle position.
    http://www.jafaphotography.com/images/eq/MYM645PTK1.jpg

    Then I found him

    spring.jpg

    I had a look on the web and foud this service manual page, which is maching the fact I had a mirror problem and all.
    https://flic.kr/p/dhwBR3

    Anybody already experienced that with this mamiya and could correct the issue ?

    Thanks folks.
     
  2. darxmurf

    darxmurf Member

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    Don't know if somebody is interested in but :

    Here is the situation.
    The part #6200-24611 is broken. As it's made of plastic, it's not that strong...
    The spring which felt down is keeping it in position.

    Originally it's mounted like this
    mamiyaspring.jpg

    Apparently this part discontinued and honestly I don't think it's super useful to have the possibility to adjust it with a screw...
    Anyway, I will try to make a new one from aluminium and let you know if it's ok :smile:
     
  3. darxmurf

    darxmurf Member

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    Hi again,

    I could replace the part with a home made one.
    Now I have to perform a mirror "calibration" to adjust the focus but what's the best way to do that ?

    Thanks in advance !
     
  4. jvo

    jvo Subscriber

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    not only...

    not only a good detective, but master craftsmen, and a photographer as well - if i wasn't married, (and you could boil water), wow!:tongue:

    jvo
     
  5. rbultman

    rbultman Subscriber

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    Here is a totally made-up method which I think should work. I had a similar issue with a 645 Super and essentially used the equipment below to diagnose the problem. I did not fix it but the issue was the mirror stop that you so skillfully replaced.

    You will need a tripod, ground glass, some subject to focus on, and a means of adjusting your new mirror stop.
    Place the camera on the tripod.
    Remove the prism or finder.
    Open the rear door of the back and remove the insert. You should see the film rail that the film rests on when the insert is loaded in the back with film. The ground glass should be placed on the film rails with the frosted side towards the lens. If you don't have a ground glass, you can use a "spare" focus screen or a piece of frosted cellophane tape.
    Set the shutter speed on B.
    Remove the dark slide.
    Focus on the subject. Using the focus screen. Use a loupe if necessary. One suitable subject is a ruler which will allow you to check the exact focus point.
    Press the shutter button and hold it. Alternatively use a cable release if you have one available.
    Check the focus on the ground glass.
    Release the shutter button.
    Adjust the mirror stop as needed until the image match.

    Good luck!
     
  6. darxmurf

    darxmurf Member

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    Well, I'm quite good in the kitchen too ... :whistling:

    Cool, it was more/less what I was thinking ! Thanks !
    Sweet, I have something to do this Sunday :D

    In Switzerland, the Mamiya importer is asking 200$ to do the job ! hu ! :blink:
     
  7. rbultman

    rbultman Subscriber

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    I ended up buying a nearly new Pro body for $100. But, I still have the Super and would fix it if the part is not too difficult to make. Can you post some details regarding your repair?

    Thanks,
    Rob
     
  8. darxmurf

    darxmurf Member

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    Hi all !

    And here is the story !

    [ THE TOOLS ]

    - the "replacement" part -

    _MG_7500.jpg

    _MG_7503.jpg

    Talking about precision, I can say I did it with the softness of a backhoe... but the result is not too bad :D
    I just need to fine tune it a bit but it works !

    The main part is made from a spare aluminum IKEA part and the brass part is from a computer screw system. I glued them together (it looks ok for the moment but not sure if it will stand for a long time with repetitive mirror shocks.)

    - the spring -

    As I broke the original spring, I could not use it. At first I wanted to remove it and build a "locked" part but as the mirror is falling quite heavily, I think it's not too bad to have a minimum of shock absorption... the original spring was a bit "complicated" to reproduce (kind of "reverse spring", pulling the part), I decided to make it simple and replace it with a classic spring I borrowed from my pen :D
    It works quite well, I can see the part moving and comming back in place when the mirror falls on it.

    - the focusing glass -

    _MG_7506.jpg

    Again, thanks ikea for your cheap stuff, I could cut a piece of glass from a photo frame.
    I tried first to blur it in my sandblasting machine. Although the result was quite nice, the "grain" was a bit heavy and the projected image on it was a bit like a Pointillism painting :D impossible to focus anything on it :D

    So, I did another test using sandpaper... takes more time than the sandblasting but the result is much more fine !

    - accessories -
    tripod, small screwdrivers, paper tape, cutters, beer

    [ THE PROCESS ]

    Put the part back in the camera.

    _MG_7504.jpg

    First, remove the film rolls stuff and tape the focusing screen in the bottom of the back. As there is no film plane mark, I suppose this choice is correct...

    focus.jpg

    Then the game begins...
    Mount your camera on the tripod, it should not move during the procedure, and keep the back open. Choose something to focus, put your camera on "bulb" and shoot. While the curtains are open, you will see the "picture" on your home made focusing screen. Adjust the focus of your lens while you check the sharpness of the image with a good magnifier. When the focus looks ok, release the shutter and check the focus on the top focusing screen. If not good, remove the lens, adjust the baby screw to move the mirror position, put the lens back and check focus... do that until the focus is correct on both focusing screens

    I did it yesterday and loaded a film in the camera. I will shoot it today and check if everything is fine :smile:

    Thanks for your attention and sorry for my english :munch:
     
  9. rbultman

    rbultman Subscriber

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    Very clever. Nice way to reuse non-camera parts.
     
  10. darxmurf

    darxmurf Member

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    Yay !
    Everything is fine, did shoot some random pics at different apertures and all good !