Jupiter 8 problem

Discussion in 'Leica and Rangefinders' started by ivan_pavicevic, Feb 19, 2009.

  1. Hi rangefinder comunity ;-) I have a problem with Jupiter 8 lens on Zorki 4. Lens was bad serviced before I bought that, I think, and distance and F-stop rings are unsynchronized with "depth of field scale" (the ring between distance and F rings). So, when I set to f/2, the scale shows ~f/2.8, and if I set to f/22 the scale shows more than 22. Also, when I focusing 1m distant object the distance scale shows a few meters, and vice versa. There is need of extra force to focusing, so I think that I should lubricate somehow... I desperately need help because this is my first Zorky and my entrance to rangefinder world.
     
  2. The aperture ring can be adjusted by loosening the 3 tiny setscrews you'll see around the ring. Be extremely gentle with these because the metal is thin and very soft so it is very easy to strip the threads. I don't recall if the focus ring can be adjusted the same way. There were several versions and the assembly may be different for your particular lens.
    As for lubricating the focus, you may be able to do so without disassembling the helicals. I was able to get mine moving smoothly by lubricating just the back part of the lens, I think after removing the lens mount but I can't remember for sure now. I still have the lens and I'll take a look at it when I get home to see if I can give you any more info, but it was a while ago that I lubed it and I can't remember exactly what I did.
    My J8's aperture ring still needs relubing, but after destroying one lens (stripped the threads on the aperture ring) I left my second one alone. It is very difficult to change the aperture in the winter, but it works fine when the weather is warmer.
    Edit: I found the link to the Jupiter 8 "service manual" that I used: http://www.pentax-manuals.com/repairs/j8service.pdf
     
  3. Ran out of time to edit the previous post a second time.
    My lens is the 4th type in the "service manual." After removing the keeper ring at the back of the lens, relubricating the parts of the lens that contact the face of the keeper ring was enough to smooth out the focus ring on mine.
    I would avoid separating the lens unit from the focus unit if at all possible. After I did that on my first (destroyed) Jupiter 8, I could not reassemble them properly. The metal used is too soft and deforms too easily. If I tightened the two units together in the least, the aperture ring would bind. If they were not tightened, the lens unit would rotate with the aperture ring (glue in the threads would probably fix this). I'm sure the focus was messed up by this so rather than try to realign the lens and fix the aperture ring, I decided to just buy another lens.
     
  4. I downloaded the manual. After I read carefuly I recognized my Jupiter 8 as 4th type. In past an hour I demounted lens, but I just relubricated and then remounted it a minute ago. Well, problem is much deeper, now I think that this J8 fabricated wrong. It seems that some '62 series were "trash" (I conclude that in chat with my friend, SSSR camera collector). My J8 is No6261633, so suggesting everyone first to check 62##### series...
    I decided to just buy another lens.​
    Well James, I'll do it too :)

    Thanks James! And sorry if my English isn't good (enough understandable) :)
     
  5. Ivan,
    Unfortunately a lot of these lenses have been taken apart and put back together wrong. Sometimes it's very hard to figure out whether it's the lens or your camera's rangefinder cam that's the problem unless you have a good camera to mount your lens on. I hate to say it, but you might as well buy another camera and lens (since the price of just one is usually not that much different than the pair) and hope things go better. The Zorki 5's seem to have less problems.
     
  6. Thanks Steve! Unfortunately nowadays it is difficult to find good SSSR rangefinder in my Serbia... and costs for transport from eBay can be as much as some solid digital (Serbia isn't in EU, yet) But I will try to find new lens.
     
  7. The problem with the J8 is that neither rangefinder coupling nor focus can be adjusted easily.
    Adjusting the focus is done by placing shims between the optical block and the focussing helicoid mechanism. If these shims are missing, or have wrong thickness (i.e. come from a mount which does not belong to the optical block), it is not possible to get sharp pictures. The same applies if one of the lens elements is swapped.
    The J8 has THREE helicoids: one for the focussing ring (it moves slightly back and forth as you turn it), one for the optical block and a third one for the rangefinder coupling mechanism. All these threads are multiturn threads and can be assembled in several positions. However, with some trial and error you can get the positions right. The rangefinder coupling mechanism is factory-set (small threads are drilled into the coupling barrel, sometimes you can still see the marks left by the adjustment staff). First thing to check is whether the back of the coupling piece has correct distance relative to the mount flange, I think for LTM lenses it is something like 7mm when set to oo. If this is not the case, the coupling mechanism is either assembled the wrong way or cannibalized from a different lens barrel.
    Due to the three helicoids and the tab which runs in the slot of the rangefinder coupling piece there is always a lot of friction in these lenses. (I found the innards of mine covered with something which must have been surplus tank caterpillar grease from WWII.) I tried to re-lube mine with light silicone grease but it was still very stiff. Removing the silicone and applying some silicone oil, blended with graphite powder, yielded acceptable friction.
     
  8. Winfried, your story is basically true for every LTM lens except 50mm's - they are much simpler and generaly have only one helicoid.
     
  9. Sorry for probably confusing some people - my post rather relates to the Jupiter-9 which is a real pain to re-assemble. Anyhow, there are non-50mm LTM lens barrels which are designed MUCH easier - and have an easy-to-adjust focussing mechanism and rangefinder coupling.
     

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