Jupiter 3 problem

[santino]

Hi all!

I've got a problem with my new J3 (its actually from '54, so it's only new to me 😉
I've noticed that somebody took it apart because it didn't drive the RF to infinty (in other words, it was totally off) and the focus was tight so I decided to relube it. So far all was good but now I can't reassamble it (I've got two choices, I can pic between a correct RF or a correct meter scale and no correct RF alignment like it was when I picked it up).

Whats the matter with that lens? Did somebody use different parts and it's messed up???

any help would be greatly appreciated, It would be my fastest lens 🙂

 

[lubitel]

this is a case for kim.

have you taken a look at his repair pdfs?

http://www.pentax-manuals.com/repairs/j3service.pdf

 

[Kim Coxon]

Try searching Brian Sweeny's posts. He did a thread on relubing a J3. There is a digest of it on my website here. http://www.pentax-manuals.com/repairs.htm

You have not chososen the easiest of lenses to work on and there are differences between them.If you are still stuck, get back to me.

Kim

Hi all!

I've got a problem with my new J3 (its actually from '54, so it's only new to me 😉
I've noticed that somebody took it apart because it didn't drive the RF to infinty (in other words, it was totally off) and the focus was tight so I decided to relube it. So far all was good but now I can't reassamble it (I've got two choices, I can pic between a correct RF or a correct meter scale and no correct RF alignment like it was when I picked it up).

Whats the matter with that lens? Did somebody use different parts and it's messed up???

any help would be greatly appreciated, It would be my fastest lens 🙂

 

[Kim Coxon]

Not quick enough!!!!!!!!!!

Kim

 

[vicmortelmans]

Hi,

very interesting! I bumped into the same problem a while ago. I've reported my solution on this forum:

http://www.rangefinderforum.com/forums/showthread.php?t=21694

Maybe my solution won't appeal to you, but I think the analysis-part may be of interest anyway. For focusing-stuff, start reading at "PAPER FILM".

Just for the record: I'm still using the Jupiter lenses and have no (obvious) focusing issues. I must admit I did not perform a thorough test.

Groeten,
Vic

 

[santino]

thanks for your fast replies, I'm going to give it a try reffering to your manuals.
I once relubed a J9 and it's def. a complicated lens but I just marked all important things and took pics of them but it wasn't off when I got it, but the J3 is way off .

 

[Kim Coxon]

Hi Vic,
I saw your thread, Vaseline is a very bad idea with lenses. Not only does it go liquid at low temps, but it migrates quite badly. Many people suggest using vaseline fo a soft focus effect. 😉 It is best to use a fully synthetic grease rather than a petolium based one to reduce to effect of the grease "bleeding".

Adjustment of the main shims should be done at infinity. If the close focus is then out, you have to change the shimming between the front and rear groups. Depending on which way they go, you wil then have to adjust the main shims again in the same way. ie if reduce the thickness of the intergroup shim, you will need to reduce the thickness of the main shim. This is not too bad on a J9 though in an extreme case, you may need to thin the front aperture ring to allow the lens group to seat properly. It is more difficult on a J3 and may need some machining of the body especialy with the later ones. The rubber band idea may be good whilst you are setting the lens up but I wouldn't rely on it long term as it is too unstable. It is not too difficult to thin some of the shims and if you need to make one, you can cut one from a thin walled can but it is normally easier to make one by soldering some copper wing into a ring. If this proves slightly too thick, you can either file it down or for small adjustments, beat it thiner with a hammer but watch for ring "growth".

Kim

Hi,

very interesting! I bumped into the same problem a while ago. I've reported my solution on this forum:

http://www.rangefinderforum.com/forums/showthread.php?t=21694

Maybe my solution won't appeal to you, but I think the analysis-part may be of interest anyway. For focusing-stuff, start reading at "PAPER FILM".

Just for the record: I'm still using the Jupiter lenses and have no (obvious) focusing issues. I must admit I did not perform a thorough test.

Groeten,
Vic

 

[GeorgesGiralt]

Santino,
I've dismantled my J3 (1962 vintage) and when re assembled performed like yours BEFORE you stripped it down.
It took me a while to re thread correctly because I was thinking I changed thread start but actually did not. So be carefull, and you'll find the correct starting thread to have the RF and the lens both good.
(in fact, the ring retaining the f stop blades jumped on me upon dismantling, and guess what ? I turned the lens upside odown to figure the origin of this part... Re assembling the aperture is something longer than finding the starting thread.....)

 

[santino]

.. Re assembling the aperture is something longer than finding the starting thread.....)

I bet, I did it only once on a 135mm lens in Y/C mount because the blades were "oily" and it didn't work and I swore myself that I wont never ever reasseble a aperture again unless it's really a good lens 😀

 

[santino]

URGENT UPDATE: My J3 is from 1951 🙂