jupiter 3 repaired

[jtcliff]

I hope this helps someone.

I have a clean J3 lens that refused to focus farther away than about 20m when wide open. The rangefinder could not overlay the two images and the film was out of focus too. I sent it away and got it back in no better condition.

After hours of disassembly, shimming and reassembly I finally found the answer.

1. Unscrew the lens unit from the focus unit

2.Find and take out the two focusing location screws (180 degrees apart)

3 Take out the screw which limits the aperture rotation

Do this and you may discover this fact which solved my problem.


The three screws look identical but they NOT. One of them has a slightly smaller head than the other two. THIS IS THE SCREW THAT LIMITS THE ROTATION RANGE OF THE APERTURE SETTING. The other two are the location pins for the focusing movement.

In my lens someone had replaced them incorrectly. This caused the lens unit, when reunited with the focus unit, to be positioned too far back and never reaching the infinity position.

So replace the smaller headed screw in the correct position (the aperture limiting position) and the two identical screws 180 degrees apart and the lens unit will line up with your rangefinder cam perfectly. It did for me anyhow.

I hope all this makes sense to anyone struggling with the same problem. Best of luck.

 

[hanskerensky]

Good information. Thanks for sharing !

 

[biginovero]

This might help solve many j-3 problem as well.

As for mine which wasn't focusing at infinity I cleaned up the lenses and placed it back, then tested it, but infinity was out of focus.

After testing I disassembled and reassembled the lens, screwing back the lens assembly with force: the assembly went back in place so much more than before so that I saw the most rear flange now protruding out of the lens much more than before.

I have to test it now, but I suspect that what you say happened to you might also be at work here.

Will see.

Do you happen to have some images of the screws involved in this process?

 

[Sarcophilus Harrisii]

What sort of camera does this lens mount to?

 

[ray*j*gun]

You said you sent it away.... who did you send it to?

 

[jtcliff]

The lens is LTM mount. Fits my Leica IIIf, Bessa R, Fed etc.

The attempted repair was by a reputed person with many positive referrals.
I just think that this J3 problem is easily overlooked and, obviously, only applies to lenses previously worked on. Lay out three screws next to each other and then pick them up randomly . . . I will leave the statistical calculation to you. The difference in head size is very small.

 

[Sarcophilus Harrisii]

The lens is LTM mount. Fits my Leica IIIf, Bessa R, Fed etc.

The attempted repair was by a reputed person with many positive referrals.
I just think that this J3 problem is easily overlooked and, obviously, only applies to lenses previously worked on. Lay out three screws next to each other and then pick them up randomly . . . I will leave the statistical calculation to you. The difference in head size is very small.

It is always helpful to know the mount and camera system, various Jupiters were made in a variety of different RF and SLR mounts and it can help members looking for info find pertinent threads easier. Thank you for letting us know what it fits, and congratulations on the result.

 

[jtcliff]

I really do not want to breakdown the lens again but in answer to the request for photographs let me head you to Brian Sweeny's photos at
http://www.pentax-manuals.com/repairs/j3service.pdf

On page 9 there is a close up of one of the two focus pins. The other is 180 degrees around the other side.

The aperture ring stop pin that caused me trouble is harder to see, but on page 5 you will see a silver ring on the right. A little to the left of the silver ring there s a black slot which goes around one third of the piece and the pin projects into the slot to limit the aperture ring to the range of f1.5 to f22. That is the pin that, if too long, will not allow one to screw the lens unit closer in thus allowing it to reach the infinity position.

 

[ray*j*gun]

The lens is LTM mount. Fits my Leica IIIf, Bessa R, Fed etc.

The attempted repair was by a reputed person with many positive referrals.
I just think that this J3 problem is easily overlooked and, obviously, only applies to lenses previously worked on. Lay out three screws next to each other and then pick them up randomly . . . I will leave the statistical calculation to you. The difference in head size is very small.

The tech should be told for his future benefit. Thanks for sharing Brian's instructions.