Home

Please support mflenses.com if you need any graphic related work order it from us, click on above banner to order!

SearchSearch MemberlistMemberlist RegisterRegister ProfileProfile Log in to check your private messagesLog in to check your private messages Log inLog in

Jupiter 8 relube
View previous topic :: View next topic  


PostPosted: Tue May 17, 2016 4:28 pm    Post subject: Jupiter 8 relube Reply with quote

Okay, I don't completely suck at trying to take lenses apart but almost. I have a Jupiter 8 50 / 2 , serial# starting 58.. , "PT3030" - http://www.sovietcams.com/index.php?-483601546

This person here https://www.youtube.com/watch?v=x82K2k6lfWc (don't know what he is saying) has a similar type and he unscrews the focusing barrel by just twisting the top part, down to and including the aperture marks for the aperture ring counterclockwise. Similar to http://www.pentax-manuals.com/repairs/j8service.pdf :

"Firmly grip the lens unit and unscrew it
from the focus unit." Yeah, OK: The aperture ring appears stopped by a pin or something. I kept twisting, as hard as I could, and now the aperture ring appears quite stuck. No tendency whatsoever that it would be unscrewable.

What is there to say?

Edit. Haha, it did unscrew in the end, I just had to really twist it. Of course the aperture wheel is still stuck from my prior attempts so the lens might not be usable again. It's about how some people intuitively know how mechanical things work and how others must break a couple of instances before they learn how to handle a certain something.


PostPosted: Thu May 19, 2016 6:50 pm    Post subject: Reply with quote

Right, didn't sabotage the aperture ring then, and have relubed the focus helix with S10, just the right amount of resistance.

Followed the pdf linked to above to the last page because the aperture ring, typical of the species, had a horrible feel too from dried up old grease.

"To re-lube the ring, first remove the index pin marked
here in yellow. Next remove the lock ring screw
shown in green. The ring will now unscrew and the
two halves can be separated. " - Did that, and the two halves now can be turned round and round, what they do not do however is unscrew from each other. It's as if some threads need to meet except the halves haven't moved out of vertical alignment yet, they are as when the two screws were attached. Someone with an idea?
Edit. Ah..."ring" Razz Will try and get that ring off, tricky to grip.

Further, I should have paid more attention the the index pin screw because it should sit in a slot and it isn't immediately apparent how to make it stay put in a slot, so can't abandon ship now and reassemble. If anyone has relubed the aperture ring of a silver Jupiter 8 it would be interesting to hear of their experience with this.


PostPosted: Fri May 20, 2016 3:55 am    Post subject: Reply with quote

What grease did you use?


PostPosted: Sun May 22, 2016 10:00 am    Post subject: Reply with quote

Click here to see on Ebay

I've just reassembled it..got the ring off with a thick kind of needle thing, what you'd use to attach things to a cork board. Via a friend because I couldn't figure it out. As for the rest, http://www.pentax-manuals.com/repairs/j8service.pdf is generally good but the "lens mount ring" and "keeper" ring both turn directly against the rest of the focus unit and as such need to be lubed: it isn't just the aperture mechanism and focus helix that need grease.

Next, try and see if I got infinity focus right.. ah.

There were two issues originally with the lens: dried up grease everywhere-horrible feel to focus and aperture rings and two: mounting the lens on an adapter makes the focus ring very hard to turn. The first issue was fixed by dissassembly, cleaning and relubing (in fact it's now got a better feel to the focus ring than the CLA:d -56 J8 I bought as well as the black one fro the 70s), the second issue remains unchained. I suspect the inward pressue of the screwed-on adapter pushes the outer part of the focus mechanism too close to the inner on one side, perhaps it was dropped or subjected to an extreme temperature/change. It doesn't look much different than the -56 but something has obviously gone out of spec.