Question, re: cleaning Jupiter-8

[Apostata]

Hello all,

I took apart my J-8 after I found that the aperture ring just wasn't responding anymore. A little scary, but I got it all apart. My question is this - and pardon my lack of terminology - but the housing that I'm left with, the cylindrical piece which holds the aperture blades w/ the housing that turns the blades up or down (ie. the very thing I'm trying to lube) - is there any way to separate the housing from the shaft that it covers? I don't see how I can a) remove the old lube and b) insert new lube - all I have exposed of the interior shaft is the little bitty part that the fastening screw sits in. There's no way for me to either clean or apply new grease - and thus the whole point of my taking it apart seems for naught.

Any help appreciated.

Matt

 

[Kim Coxon]

You can download details from my website here: http://pentax-manuals.com/repairs.htm

Kim

 

[Spyderman]

If I get it correctly you want to remove the aperture setting "tube" from the main lens "tube". To do this you need to unscrew the screw that translates the movement of the outer tube to the aperture blades. Then you can slide the outer tube off and clean it.
Or take a look at Kim's manuals...

 

[Apostata]

Hey guys,

Thanks for the responses. Here's the problem: I've removed the retaining screw, but I can't seem to remove the housing from the inner column. I've attached a scan of the piece so you can see (notice all the old grease built-up around the ring). I can turn the outer housing around, but it seems not to be able to separate - which way does it come off?

Thanks,

M

 

[Spyderman]

Please do take a look at Kim's pdf tutorial on this page: http://pentax-manuals.com/repairs.htm

It's obvious you need to take off the ring just above the aperture setting-tube which is again secured by a tiny set-screw. (In the picture it's just above the aperture setting tube.)

 

[Apostata]

I figured it out - even with the screw out of the retaining ring, it was really tightly mounted. After applying some lighter fluid to remove the excess old grease, the ring loosened very easily. I can't believe I managed to put it back together again after cleaning it...I'll be even more surprised if everything's in focus 😀

BTW - is there any problem using "lens cleaner" for cleaning the internal glass elements?

Thanks again,

M

 

[Apostata]

*sigh* Crap. Can I assume that, if nothing is in focus in the viewfinder, then I don't have the lens pieces aligned properly? Neither infinity or close-up are in-focus.

 

[wolves3012]

*sigh* Crap. Can I assume that, if nothing is in focus in the viewfinder, then I don't have the lens pieces aligned properly? Neither infinity or close-up are in-focus.

No you can't on an RF! The viewfinder image bears no relation to the lens focus on an RF...or did I miss something here?

 

[Apostata]

My mistake...I must've turned the focus-correction knob on the viewfinder itself. This is what happens when you're staring at small screws for 3 hours.

 

[wolves3012]

My mistake...I must've turned the focus knob on the viewfinder itself. This is what happens when you're staring at small screws for 3 hours.

If you've been using Kim's site then you shouldn't be far out. I'm not sure you can actually put a J-8 together wrongly unless you do something like reversing elements or leaving shims out. Depending on the camera you have, you can do a check by taking the back off and putting some opaque tape over the film gate (or use an old SLR screen or similar) and checking the focus on that.

 

[Disaster_Area]

sorry to hijack this thread, but I'm having a bit of a problem with my jupiter 8 as well, I've read over Kim's guide and it looks like I have a version 3 lens according to her tutorial. I'm trying to take it apart and I just CANNOT get passed the first step, unscrew the lens unit from the focusing heliod 🙂 .. I'm not a weak guy, I've tried heating it a bit in front of a space heater, I tried using rubber cloths.. am I missing something or has the lube turned into some kind of super duper nasa quality glue over the years? I'm gripping the lens by the mount and twisting counter clockwise on the end of the lens, trying to grip it by the aperature dial, but by the end of the lens.

 

[Spyderman]

Mine was also really tight to remove. I had to heat it in oven to about 60°C and then use rubber cloths but it was still very difficult to unscrew.