New J-8's - how do you dismantle them?

[fraley]

Hello,

I have two of the 'new' Jupiter-8's, the black models that rotate the aperture ring along with the focus ring. One has a stiff aperture ring, and the other lens has a loose aperture ring. I'd like to take them apart and either thin or thicken the lubricant to get the desired smoothness.

Kim Coxon is very good at this -- he did two early silver J-8's for me and has a great website. I think the construction is different on the newer J-8's, though. He says to grasp the lens unit firmly and unscrew it from the focusing unit. I've done this on older J-8's, but on these black ones I feel like I'm forcing it, and it will break. Nothing gives. Also I read somewhere about loosening the set screws in the aperture ring and unscrewing it. Again, I am having no luck. Anyone familiar with these models and how to take them apart?

Thanks,
Michael

 

[Kim Coxon]

Hi Michael,
No all the black ones are the same as the silver one that I showed in my instructions here. http://www.pentax-manuals.com/repairs.htm

They can be very stiff. It could be a different version but I think it unlikely. The only FSU lens I have come across so far that the front unit is "locked" with set screws is the J11. Hopefully instructions for this will be posted soon.

Kim

 

[varjag]

My friend did a service to black J-8, and found out there is no lens unit per se. The lenses are mounted right in the focusing assembly.

 

[Kim Coxon]

Hi Eugene,
If you check out my link below, you will find this isn't so. The whole lens rotates as you focus which is somewhat unusual but they are two distinct modules. The front one with all the glass and aperture can unscrew from the rear body whih has the focus helix in it.

Kim

My friend did a service to black J-8, and found out there is no lens unit per se. The lenses are mounted right in the focusing assembly.

 

[fraley]

Thanks Kim, I will give it another go!!