Another Pentax 67 problem...

Discussion in 'Medium Format Cameras and Accessories' started by batwister, Sep 21, 2012.

  1. batwister

    batwister Member

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    A new problem with my Pentax 67. Putting the speed at 1 second caused a strange shutter problem today, one that gave me no choice but to waste half a roll trying to figure out what was going on. When I put the shutter dial at 1 second and pressed the MLU switch, the aperture blades stopped down to f/22 (correctly), for about a second (judging by ear), then the mirror went up and the blades opened up again. Then, upon pressing the shutter, the the mirror went down immediately, leading me to believe the MLU switch made the exposure. How can this be!?

    I can't believe how mischievous the 67 is. After unloading the wasted roll when I got home, I tested the camera in dry mode at 1 second again with MLU engaged. Worked perfectly!
    Why does the shutter suddenly take on a life of its own when film is loaded?
     
  2. dpurdy

    dpurdy Subscriber

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    Poltergeist! Has the camera seen heavy use in the past? They are very durable but eventually parts will start to wear out.
     
  3. batwister

    batwister Member

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    It was a college studio camera. I've recently got it back from a repair.
     
  4. Hatchetman

    Hatchetman Subscriber

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    did you change the lens right before by any chance? that sometimes messes things up.
     
  5. batwister

    batwister Member

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    I only have one lens so didn't change it. Very curious as to why the shutter only does this when film is loaded though.
     
  6. Poisson Du Jour

    Poisson Du Jour Member

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    Are you sure you are following the 67 at the moment of actual exposure? MLU comes first (initiated by you), then you shortly after, triggering the shutter and, by dint of that, stopping down the aperture blades. It is not in the realms of possibility for the process to be reversed or for MLU to emulate the shutter: it has no connection to the shutter; it's only connection is to the mirror with electrical connection to two solenoids to bring it up and magnets to throw it down. But...

    ...if the prism/lens reattachment process is not followed, unpredictable results can occur because the aperture coupling is not engaged, so there is no coordination between the lens aperture and the camera coupling. Remove the prism. Remove the lens (this resets the position of the aperture coupling to null. Then replace the prism. And replace the lens, in that order (this will link the aperture tang and coupling chain correctly). Load a dummy/exposed roll of film and go through the process carefully again.
     
  7. batwister

    batwister Member

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    I followed your reattachment advice, loaded a dummy roll and everything went smoothly. But who knows what will happen when I shoot a new roll tomorrow!
    Is it really possible this coupling thing was causing the erratic shutter problem? If so, simply removing the lens before the prism can cause such a major problem, leading to lost frames? I just wonder how the camera could have been engineered in such a silly way.

    Today when I engaged MLU, the mirror didn't move immediately, there was a lag of about a second. Then when the mirror did move, the aperture blades opened fully rather than staying at f/22 as set. Then when I pressed the shutter, the mirror this time dropped immediately, even though the shutter dial was set to a second. That second pause when I pressed the MLU button led me to believe MLU made the exposure, as it was the only time in the process when there was a pause in the camera mechanism.
     
    Last edited by a moderator: Sep 21, 2012
  8. dpurdy

    dpurdy Subscriber

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    The prism and lens order have to do with the meter working. If you happen to take off your prism with a lens on the camera and then put the prism back on the meter won't work. You have to have the prism on the camera and then put the lens on for the meter to work.
     
  9. batwister

    batwister Member

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    The prism I have is just the standard pentaprism, non-metered.
     
  10. Poisson Du Jour

    Poisson Du Jour Member

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    Yes, the prism needs to be coupled to the lens aperture lever or the mechanism will not engage and thus potentially snap the coupling chain — an involved and extremely fiddly repair job that is a bit like repairing a watch.

    Process is: prism off, then lens. Replace the prism, then re-mount the lens. Ensure the prism coupling pin engages positively with the shutter speed dial. If the prism has a switch, turn it on to verify the meter is reading at the selected aperture/shutter speed value (if in low light, switch to bulb and maximum aperture of lens: needle should shoot up to the top). If the prism has been correctly fitted/coupled, it is safe to change just lenses any time you wish.

    The prism is generally only removed to facilitate cleaning of the focusing screen.
     
    Last edited by a moderator: Sep 21, 2012
  11. Brian C. Miller

    Brian C. Miller Member

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    Send the camera back to the repair shop. You shouldn't have problems like these with it.

    When the MLU is tripped, the mirror goes up, and the shutter stays put. Then when the shutter is tripped, the first curtain fires, and a second later the second curtain fires. I have a P6x7, and I've never experienced what you described.
     
  12. Poisson Du Jour

    Poisson Du Jour Member

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    Brian C. Miller's second paragraph is correct in terms of operation.
    At the moment, and having noted your post that you have the non-TTL meter version prism, I am thinking something may not be coupling correctly irrespective of the prism/lens mount-dismount procedure. I would take the prism off and scrutinise the coupling chain; if it is broken (and a broken chain is conspicuous by its floppy appearance), that's a proper repair job. If it is intact, attention needs to shift to the coupling level in the lens mount. After those checks and operational tests, only then should the camera go in for service; because of this camera's engineering quirkiness, problems can and do manifest in unique and different ways — frustrating/infuriating ways, if you like. Never had this sort of problem with my 67 but then I read the instructions before I started removing things (just this afternoon I removed the prism top remove a stray hair that was annoying the crap out of me on the focusing screen — reassembled, loaded with Vaudeville Velvia and ready to roll).
     
  13. sbjornda

    sbjornda Member

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    That's only true for the metering prism, correct? I believe the OP said he had the non-metering prism.
    Or to switch between prism and another finder, e.g. Waist Level Finder or Chimney Finder.
     
  14. batwister

    batwister Member

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    I've shot a couple more rolls and haven't had the problem I've described, but the mirror will still stick occasionally. Turning the speed dial a few times will release it.
     
  15. Brian C. Miller

    Brian C. Miller Member

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    The mirror should never stick. You are still having problems with the camera, and it needs to go back for more service.
     
  16. John Wiegerink

    John Wiegerink Member

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    Good, fresh battery? Of course I think the "mirror-up" is mechanical.
     
  17. Poisson Du Jour

    Poisson Du Jour Member

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    It is electrical, controlled by solenoids on the upswing and magnets on the return. It can exhaust the battery, but only if it is held up with shutter tripping.
     
  18. Poisson Du Jour

    Poisson Du Jour Member

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    Check the foam damper on the forward lip of the top of the mirror box has not deteriorated to the point where it can cause the mirror to stick to it. Replacement foam can be obtained on eBay and it is very good stuff.
     
  19. batwister

    batwister Member

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    Since this problem is still ongoing, I'd like to keep correspondence here. The comments have been helpful, but I'm still trying to figure it out.
    I've been in contact with the repair guy and haven't had a response. I really can't afford for another repair place to take advantage of my ignorance about the problem.
    The shutter box was quoted as being repaired in my receipt.

    There's still a roll of film in the camera which I'd like to try and finish before checking the foam, as suggested by Poisson.
    Since the shutter doesn't stick when I'm quick about making an exposure (activating MLU and pressing the shutter) it sounds like this might be possible. If I activate MLU and faff about making light readings before pressing the shutter, it takes a while for it to drop down - my lull giving it time to stick?. But other than this potentially being the cause, what else would cause the mirror to stick? With a fully functional 67, after pressing the shutter, how does the mechanism work exactly to drop the mirror?
     
    Last edited by a moderator: Oct 1, 2012