Fujica ST-901 mechanical times

Discussion in 'Camera Building, Repairs & Modification' started by Eugen Mezei, Oct 22, 2012.

  1. Eugen Mezei

    Eugen Mezei Member

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    Bought a package of cameras described as nonfunctioning. Gambling you know. A Hi-Matic E works and I thought at first sight this black ST901 does the same.
    On second sight it doesn't.
    It works just fine in auto mode, shutter speeds seem accurate.
    But when changing to manual the shutter doesn't open. Advance is working, the mirror slaps but the shutter stays closed. It seems the first curtain is coupled with the second and just drags it with it. This doesn't happen in auto mode. I thought at least 1/60s and B are purely mechanical.

    Any ideas how to fix this, besides using the camera just in aperture priority AE mode?

    Greetings,
    Eugen
     
  2. lxdude

    lxdude Member

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    What I can tell you is the mechanical shutter speeds are B, and from 1/60 to 1/1000 second, and to use them them you just select them on the shutter speed dial. The mechanical shutter speed chosen will be shown on the left side of the finder. The indicator in the finder on the left should display whatever is chosen on the dial.

    If I understand correctly, the shutter will not open at any mechanical speeds.
    I would suppose there is something wrong with a linkage somewhere. It could be the dial is not transferring the setting to the mechanism. I suspect the camera was dismantled and something was not put back together right.
     
  3. Eugen Mezei

    Eugen Mezei Member

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    Thank you lxdude for confirming I don't make a handling the camera mistake. Yes, it shows in the finder A, B or the speed as selected on the dial.
    I opened the bottom plate, there anything seems to work as it should. I won't take the risk to open the upper cap of the camera. (Last time I did let the camera with broken wires.) The screw holding it seems to be screwed in angled, so it is very much likely somebody worked in this camera.

    Any idea what is hiding under the tiny cap upper right near the viewfinder?

    What happens when using flash? I think it would not syncronise in the state it is now.
     
  4. David Lyga

    David Lyga Subscriber

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    I think that the ST-901 is not mechanically governed, but, instead, timed by electronics. Mechanical is not the same as manual. Lxdude might be correct with some mechanical override but I can no affirm. Correct me if I err. - David Lyga
     
  5. lxdude

    lxdude Member

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    The manual speeds are fully mechanical, i.e. no battery needed.
     
  6. lxdude

    lxdude Member

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    I'm not sure what you mean by the tiny cap. To the front of the camera on the top next to the shutter dial, there is a lever which is the shutter dial lock. On the back is the lever for the viewfinder blind, and the battery chamber cap.

    You could probably get the top off without harm, if you have some knowledge about camera disassembly. One of the innovations in the ST901 was the use of flexible circuit boards instead of wiring. The flash shoe might still be wired- I don't know. If you can desolder and solder, a few wires are not a problem.

    For flash, the 1/60 speed on the dial is selected. In auto, any speed displayed below 1/60 will work.
     
  7. lxdude

    lxdude Member

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    I should have thought of this before- www.butkus.org/chinon/ has lots of camera instruction manuals, including the ST901.
     
  8. Eugen Mezei

    Eugen Mezei Member

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    David: Unfortunately every source I know (manual included) says these speeds work without batteries. I would be glad if these were times where the electromagnet is getting current for a fixed time. Than I would have good hope it is only an electrical fault somewhere near the speed dial. Too bad this isn't the case.

    lxdude: Next to the viewfinder (the window you put your eye on) is a lever for stopping light entering it. Diametrally oposite to this lever is a tiny cap. I guess it hides a screw or a hole where you can introduce a screwdriver.
    I know butkus but confess I haven't read the manual for the st901. Thought it is nothing you can't do if you already know some similar cameras.
    Problem is the soldering of aged wires. But if it is only the one to the hotshoe maybe I will give it a try. Were you in the camera? Maybe we can guess what could be bloqued or missing. How is the delay between first and second curtain realised?
     
    Last edited by a moderator: Oct 23, 2012
  9. lxdude

    lxdude Member

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    Oh, I forgot about that cap. My guess is that cap covers a hole for making adjustments to the auto-exposure after assembly- I figure there's a variable resistor or such on the other side. Another possibility is it has something to do with the viewfinder blind. I think you would not have to remove it for disassembly.
     
  10. David Lyga

    David Lyga Subscriber

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    Eugen Mezel: that probably is true: that certain speeds work without batteries. But...when fresh batteries are put in, do those same speeds then derive their function from the batteries or is the clockwork mechanism for those speeds always working? I think the latter. - David Lyga
     
  11. lxdude

    lxdude Member

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    There is no clockwork mechanism in the ST901. Clockwork mechanisms are for timing a fully open shutter. The higher speeds are achieved by narrowing the distance between the shutter curtains as they traverse.
    The ST901 has essentially the same mechanical shutter mechanism as the ST701 and ST801 manual exposure cameras, but does not have their clockwork mechanism to time speeds slower than 1/60, so it has no manually selectable speeds slower than that except B, nor does it have any speeds which are manually selectable and electronically timed. The manual speeds it has are mechanical and fully independent of battery power.
     
  12. lxdude

    lxdude Member

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    Sorry, I missed this edit before. You should be OK to desolder and resolder any wires. The wires in the Fujica ST801 (and maybe 701) had Teflon insulation, and should be good. I would expect the 901 to be the same for any wires it might have. I have not been into the ST901 or other Fujicas. I don't know the details of how the curtain distance is established.