Zorki-4 Slow Rear Curtain Travel

Discussion in 'Rangefinder Forum' started by Lamar, Jan 7, 2014.

  1. Lamar

    Lamar Member

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    I've noticed on my 1971 Zorki-4 that the rear curtain travel at speeds of 1/30th and lower appears to be slow. This is especially evident at 1/30th. Sometimes it looks ok but more often than not it seems slow. I tried adding a half turn of extra tension on the rear curtain spring but that did't seem to affect the travel. Any suggestions as to what to check?
     
  2. E. von Hoegh

    E. von Hoegh Member

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    The camera needs a CLA. Changing curtain tension from the proper settings to compensate for bad lubricants will just cause other problems. Sorry there's no quick fix.:pouty:
     
  3. Lamar

    Lamar Member

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    Yep. I was afraid that would be the answer. I was hoping that since the fast speeds work fine there may be a simple fix to this, it looks very clean inside, no dust or gunk. I hesitate to do a complete CLA myself yet. I do have a 1962 Zorki 4 I got for $15 that I have been using as a training tool. The front curtain ribbons have come loose from the drum. I have it disassembled and am learning from it but I hesitate to screw around with a mostly working camera just yet. What specific points affect the curtain travel speed and why does it only affect it at slow speeds and not fast speeds? The return spring is the driver and it is tensioned the same regardless. Once the curtain is released to return, it should travel at the same speed from what I can deduce from my "parts" Zorki.
     
  4. E. von Hoegh

    E. von Hoegh Member

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    The curtain speed is a fixed quantity, it is the same for all shutter speeds. Unless you have instruments to measure curtain travel time and shutter speed (effectively, slit width) you can't really tell what's going on, except by making test exposure - a crude method at best. If you can actually see that the curtain is sluggish, it's way out of whack. What may effect it at slow speeds (large slit width) would be poor lubrication in the drum and roller (under the shutter speed dial) and associated timing mechanisms.

    These shutters are pretty simple once you understand the theory and get used to working with smallish mechanisms. Keep practicing, you'll be fabricating your own curtains in no time!
     
  5. limnidytis

    limnidytis Subscriber

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    Sometimes I find an amazing number of film chips buried under the restricting gear in the bottom of the shutter crate in FED/Zorki cameras.
     
  6. E. von Hoegh

    E. von Hoegh Member

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    Yes - I should have mentioned to check for debris first!
     
  7. Lamar

    Lamar Member

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    What specific type of oil should I use for the shutter timing mechanisms (top) and the curtain drum shafts and winding gears?
     
  8. E. von Hoegh

    E. von Hoegh Member

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    Use a high quality light clock or watch oil, the modern synthetic oils will last for quite a few years and oils suitable for cold weather are available. But, putting oil on without cleaning the lubrication points is pointless, the new oil will be contaminated by the remains of the old oil and any dirt/abrasive contamination, also it will probably creep away leaving the parts dry. A couple watchmakers oilers can be had for $10 or less; putting too much oil on is as almost bad as none. Some points require only the slightest dot of oil (get a 2.5 - 5x loupe so you can actually see how much you apply) and other parts must be left dry. Gear teeth are typically left dry - there is no sliding contact between well cut teeth, and in a camera no inertial loads (resulting from high rotative speeds) that need cushioning by a lubricant film. Use a light grease on the gear pivot points.

    For evaluative purposes - to free sticky parts so you can verify proper operation/ troubleshoot problems - "Break Free CLP" is a useful product, it will get things moving - but it is not a substitute for proper cleaning and lubrication.

    Edit - one source for high quality oils, oilers, etc - http://www.ofrei.com/page246.html
     
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  9. John Koehrer

    John Koehrer Subscriber

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    The slow speeds are controlled by a clockwork escapement, not travel times. In Leica M cameras it's inside the camera at the bottom. Cleaning and relube is the correct answer.

    Since you've got the other camera apart you should have a clear view of the offending assembly. Naptha or liquid lighter fluid to clean it and watch oil for lubrication. The oil should be crystal clear, If it has a color to it, it's too heavy.

    the pivots of the gears and pallet are what need the attention. A pinpoint oiler will apply too much lube, Use the oiler and transfer a small drop to a sewing needle or straight pin and apply it by touching the pin to the pivot.
     
  10. E. von Hoegh

    E. von Hoegh Member

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    Whether the Zorki has slow speeds and therefore a governor or not, I don't remember. But said governor controls when the curtain is released, not the speed of travel; it wouldn't effect the shutter at all at full gate speed which is 1/30. And, a drop on the end of a straight pin is far too much for any pivot in the slow speed geartrain, indeed it would possibly be too much oil for the bushings in the curtain drums. The pallet pivots are lubricated, the pallet proper and pallet wheel teeth are not unless the maker specifically recommends it.

    Edit - for clarity.
     
  11. Aron

    Aron Member

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    Nothing like having a watchmaker among us!
     
  12. Lamar

    Lamar Member

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    As E. von Hoegh said, This is slow curtain travel at the slower speeds, not a problem with the slow shutter speeds. You can see in some of the shots as well that the side in the direction of travel is exposed longer than the upstream side of travel.
     
  13. E. von Hoegh

    E. von Hoegh Member

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    Since I havn't seen the camera, I do not know, but I'm presuming it has dry or thick lubricant on the spindle of the drum. This assembly has a drum for the first/opening curtain, two coaxial - top and bottom - rollers for the tapes of the second/closing curtain, and a floating disc that has a pin which works in slots in the top of the drum and top roller to cap the shutter when you wind it. If the disc is sticky on the spindle it can cause this problem, the wider the curtain opening the closer to a full circle the disc travels.Stiff lube on the spindle elsewhere will cause trouble too. This is pretty similar to the design used on say a Leica III or IIIa; here's a link - http://www.pentax-manuals.com/repairs.htm
    I have an old Canon IIb that had the same issue, 65 year old lubricant gets almost like shellac.

    Edit for clarity
     
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  14. q_x

    q_x Member

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    How's progress, Lamar?

    Maizenberg is the mandatory book on the subject, I think. Google, download, enjoy, if you haven't yet. I've seen it online in English and Russian.

    I've noticed similar behavior BTW, that is the rear curtain getting slow, while it was getting better and better as the shutter speed went up. It's illogical, I know. And lubrication helped a lot with the issue.

    BTW, Zeiss Ikon filters (~42mm slip-on) fit on lenses with 40,5mm thread (checked with Jupiter 8), and original cap still works, fits well inside the filter.

    Cheers!
     
  15. Lamar

    Lamar Member

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    I have made some progress. I'm learning more than really fixing anything though. I de-tensioned the rear curtain spring by half a turn and that seems to have helped. I can still see one side of the frame is a little under exposed though. I will most likely de-tension the rear curtain spring another half turn and test again. I also think the front curtain has been over tensioned, winding seems a bit stiffer than my others. I read where starting tension on these springs should be 5 turns for the front curtain and three for the rear. I almost want to just release the springs and start from scratch so I know exactly where I am on them. I wish there was an easy way to really test the shutter speed accuracy and timing.

    I haven't committed to a full disassembly and CLA yet but I did put a drop of Break Free CLP oil at a few key points to see if it would help. It did seem to make the slow speeds much more reliable. They work correctly most of the time now. I did not have a single problem with the slow speeds yesterday...... Keeping that broken Zorki-4 was the best $15 I could have spent though. I have been able to learn and test on it before I do anything to my good ones.
     
  16. Lamar

    Lamar Member

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    I found an interesting post over at Rangefinder Forums regarding checking relative shutter curtain speed. Such a simple procedure to a seemingly diffcult problem. It shows how to use a CRT to check/adjust tension on your shutter curtain springs to ensure they travel at the same speed. I have checked mine and the results were consistent with what I was seeing in the pictures from each on my Zorkis. I have now adjusted according to the post. The next roll will tell.....

    http://www.rangefinderforum.com/forums/showthread.php?t=30343
     
  17. E. von Hoegh

    E. von Hoegh Member

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    That post is dated 2006 and is just about certainly based on the frame and scan rates of the no-longer-in-use-for-broadcast NTSC 3.58 system. Unless you used an old TV (CRT not flatscreen) with an NTSC signal, the results won't be accurate for estimating shutter speeds. The new system may still show valid info for relative speeds of the curtains though. Leitz used a similar method before TV - http://www.skgrimes.com/library/old-news/the-leica-drum-shutter-tester

    By "rear curtain" do you mean the first/opening or second/closing curtain? They are not always in the same relative fore-and-aft positions on all cameras.
    If you really want fun get a Kiev - metal slats running up and down!
     
  18. Tom1956

    Tom1956 Inactive

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    Well I still use an old TV with the digital converter box. Doesn't the box convert the digital signal back to the 525 line, 7875/30 frame system?
     
  19. Lamar

    Lamar Member

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    I threw out most of my CRT based video gear last year during a clean-up but luckily I'm a pack-rat and kept a couple of my small NTSC TV's just in case. Yes, rear curtain is the second/closing, front curtain is the first/opening. That nomenclature was from Nikon manuals regarding flash sync, I'm sure others use the same reference. I never knew if "rear" was referencing physical position when looking down on the body or just the fact that it was triggered last in the sequence, bringing up the rear... :smile: