Synchro-Compur MXV and exposure time adjustment

Discussion in 'Camera Building, Repairs & Modification' started by Usagi, Apr 26, 2011.

  1. Usagi

    Usagi Member

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    I have two different Compur shutters which both has same problem.
    The times 1s, 1/2s and 1/4s are precise, so are times from 1/30s to 1/100s (above that, the speed doesn't change much).

    The problematic times are 1/8s and 1/15s, which both gives exactly same time as 1/100s position.

    I have gone thru several synchro-compur shutters, but these two are only ones with this problem.

    According to manual: http://benoit.suaudeau.perso.neuf.fr/manuels_rep/obturateurs/compur-repair/06-03.html

    The speed of 1/15 second can be adjusted somehow, but I just can't figure how.
    The repair manual suggest for bending detent pin but it sounds a bit brutale operation.
    As far as I understood correctly, the detent pin is the one marked in Fig 4 in this page:

    http://benoit.suaudeau.perso.neuf.fr/manuels_rep/obturateurs/compur-repair/04-10.html


    Anyone done this? Or is it just better to not care about that and just not to use times 1/8 and 1/15s ?
     
  2. Ron G

    Ron G Member

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    You can bend the pin but it will also break if you bend it too much so be careful with it.Be sure that the escapement is clean and do not over lubricate it,just a toothpick lightly wetted and and barely touching the bearing shaft bushings is enough.I sometimes dissasemble the escapment to clean it properly if I have a problem with the shutter speeds.Also be sure that the escapement is completely disengaged on the 1/500 setting.Ron G
     
  3. Usagi

    Usagi Member

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    Thank you very much!
     
  4. f64FTW

    f64FTW Member

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    Mee too!

    I have the exact same problem-- in my case the 1/8 and 1/15 are a stop fast. Have people had success with this issue by bending the lever per the service manual? It's weird that it affects both a time on the slow gear train and a time on the fast gear train.

    In my case, I've disassembled and cleaned the shutter in naptha/lighter fluid and re-lubricated it per the instructions in the service manual. Apart from this, it's behaving peachy-- I even have a pretty good approximation of 1/500 and the other speeds are dead on.

    thxthx!
     
  5. Brett Rogers

    Brett Rogers Member

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    Have you had the speed escapement out of the shutter? If it is not positioned correctly on re-installation the 1/15 speed will be off. If the 1/8 is also off it sounds like the one in your shutter needs to be moved more than a fraction of a mm, maybe half a mm or so to start with. You can fine tune the position of the escapement by backing off the two mounting screws slightly and gently levering the escapement with suitable implements.
    Cheers
    Brett
     
  6. John Koehrer

    John Koehrer Subscriber

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    The easiest way I've found to make this adjustment is with a piece of brass tube slid over the pin and barely touch the tube.
    An imperceptible bit is enough to do it.
    My rule of thumb is, If you see the movement, It's too much.
     
  7. shutterfinger

    shutterfinger Subscriber

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    .00005 inch is usually enough movement to position the pin.

    I've got one that gets worse every time I open it and won't run now. Appears to have been dropped as the release lever was pushed in against the case.
     
  8. Brett Rogers

    Brett Rogers Member

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    Yes, you can bend the escapement pins if really necessary however if the shutter timed correctly as it was once then there is a fair chance that with the escapement correctly positioned it will do so again. Personally I prefer to adjust the escapement position relative to the shutter housing (and hence the speed cam) and contemplate bending the escapement pins if, and only if, it's not possible to get all speeds good.