Jupiter-8 Disassembly questions

[csisfun]

Hi!

I would like to disassemble a J-8, but I can't even start on the first step, splitting the lens unit with the focus unit. My J-8 is a 1983 black version.

I tried gripping hard and twisting them in opposite directions, but to no avail - it's still stuck tight. Is there any more specific instructions? Thanks!

 

[Kim Coxon]

Hi,
There is a full guide on my website on all 3 versions of the J8.
http://pentax-manuals.com/repairs.htm

Kim

Hi!

I would like to disassemble a J-8, but I can't even start on the first step, splitting the lens unit with the focus unit. My J-8 is a 1983 black version.

I tried gripping hard and twisting them in opposite directions, but to no avail - it's still stuck tight. Is there any more specific instructions? Thanks!

 

[csisfun]

Hey Kim!

I was reading exactly that! I couldn't decipher how to do it...

 

[Kim Coxon]

Hi,
Some of them can be very stiff to start. Someone may have used loctite or similar on it and you will have to "break" that. It is a normal thread, ie if you look at the front of the lens, it unscrews anti-clockwise.

Kim

 

[Murray Kelly]

I have read your site, Kim, but I have exactly the same problem as csisfun. None of my J-8s will yield to me. Unlikely they are all glued in with Locktite.

My reason to try was that I wanted to see if a Helios-103 assembly would fit the LSM barrel. I have a couple of 103s and admire them so much I would sacrifice a J-8 for the project.

I wonder if I put it in a zip-loc bag in the feezer then out in the sun it might break the bond?

Murray Kelly
Brisbane, Oz

 

[Spyderman]

I put mine in an oven heated to about 60-70 degrees celsius. It was pretty hot to touch then, but it helped and I was able to unscrew it...

 

[Murray Kelly]

A-ha! Thanks Andrej.I will probably go down that road.
I am resigned to the result being negative (the lens and barrel won't match) but I feel
I'd like to try.
I have a tame, retired, Austrian machine maker who I may be able to help out.
Bottom line - I just want to look, see.

Murray Brisbane, Oz

 

[WJJ3]

anybody know what screwdriver size I need to disassemble my '62 Jupiter 8?

 

[john neal]

probably a couple - get the best 1mm and 2mm (maybe 1.5mm and 2.5mm, I forget and I'm at work)) ones you can find - they need good, hard, and fine square ends or you will chew up the screws.

If you can source a small set of well made ones from 1mm to 5mm you will be good for any similar job. Only more modern lenses will need Philips or Pozi drivers.

 

[WJJ3]

Thanks for the reply. I have a size .000 slot head that is slightly too big to fit in the screw heads on the focus ring. The smallest size I see online is a 0.8mm, so I'm wondering if that will do the trick?

 

[WJJ3]

Got my lens disassembled and regressed the helicoid. I had to use the tip of an exacto-knife to get the tiny screws on the focus ring...

 

[WJJ3]

Hi,
There is a full guide on my website on all 3 versions of the J8.
http://pentax-manuals.com/repairs.htm

Kim

Just want to say thanks so much for this guide! The J-8 is a pleasure to work on and this guide made it so easy. I got the helicoid and aperture ring cleaned and re-greased. I ended up using Finish Line Grease with Teflon, which I'm finding is a bit heavy for the focus, but spot on for the aperture ring.

I have to add that while I did enjoy working on the tired old J-8 that I purchased locally here on Oahu, I don't like the way the mount is designed. The diameter of the mount surface that actually makes contact with the camera mount is thin, and the mount itself has a very slight play in it. Mine is a '62. Not sure if they all have mounts like this one.

 

[wolves3012]

.... I don't like the way the mount is designed. The diameter of the mount surface that actually makes contact with the camera mount is thin, and the mount itself has a very slight play in it. Mine is a '62. Not sure if they all have mounts like this one.

Earlier lenses had the more complex mount like yours (as do the very similar Industar 26 and 61). Later lenses (including all the black ones) have a simpler helical where the whole lens barrel rotates. Not useful with (say) a rectangular lens-hood.