Jupiter-8 disassembly follies

[derevaun]

Having practiced on an Industar-26 and Industar-61ld, I took a shot at relubing my '64 Jupiter-8 (LTM). The helicoid really needed it, and the aperture was awfully loose....

Anyway, I followed the instructions for the I-26/61 on Matt Denton's site, and had read somewhere that the J-8 was the same basic design. It went smoothly, no problems, and that emboldened me to go farther into the unknown. Here are my findings:

• There's no retaining screw for the rear group, but it does unscrew with a spanner.
• Unfortunately, that's pretty much the end of the line as far as I could tell. What about the front...
• After removing the set screws on the aperture numbers ring, it can be screwed toward the back of the lens to reveal more set screws
• These set screws release the front of the lens, which hold the front element on with a pressure pad.
• The aperture numbers ring can then be screwed off toward the front of the lens, revealing the aperture ring, which is threaded for the numbers ring.
• The DOF scale ring appears to me to have materialized into place--removing its set screws just lets it spin around and reveal some inaccessible gunk underneath it.
• And, after all that, the aperture ring itself is pretty much inaccessible too.

I chickened out after that and just put it all back together after a little buffing with some Flitz metal polish and a little synthetic grease applied to the edge of the aperture ring. So I'm dying to know: how do you get at the aperture ring to lube it? How does the DOF scale ring come off?

Wait, more questions! I replaced the rear group to the markings I made before unscrewing it. I checked infinity with an SLR and it looked spot on. But after bumbling around the innards of the lens, I wonder if the close focus is right or at least matches the markings (with infinity as a reference). If I some test shots with the distance markings, do I measure in meters from the film plane, or the mounting flange, or what? At close distances it seems like it would matter. Thanks for any insights!

 

[Sonnar Brian]

I have not taken a J8 apart, but have done my J3. The focus ring and DOF scale both came off after removing the set screws. I could get to the helical. I'm going to be taking one apart and photographing it in the next week or to.

 

[Kim Coxon]

Hi,
Is this the early chrome J8 or the later black one? The two are very different and come apart in a completely different way. The chrome ones are more like the I26/I61 but the black ones are more like the J9

Let me know and I will try to provide a guide.

Regards
Kim

 

[derevaun]

It's the chrome version. Its focusing setup is just like the I26/I61 (except it was a bit trickier to get the focusing ring started), but the rest definitely did not match Matt Denton's walkthrough for the I26/I61. Nobody claimed that it did, but it was worth a try. I would like to take another shot at it, because some dust got in between the elements, but I'm hesitant because two of the set screws stripped in the process. I was able to get them back in anyway, but next time I might not be so lucky. The obvious solution is to buy another one 🙂