Servicing a Jupiter 8

[lxmike]

Hi just picked up a Jupiter 8, hopefully the post man will deliver it this week, it looks optically ok but the seller did mention in the listing the following:

'Aperture dial is a bit sticky. Focus ring moves smoothly but sticks a little at the 1 meter end stop. '

I was wondering if there was anywhere in the Uk that could sort these ailments, I'm not too opposed to a bit of DIY if need be

cheers Mike

 

[greyelm]

Is this any help?


http://www.pentax-manuals.com/repairs/j8service.pdf

 

[1750Shooter]

There's also a sticky here @ FSU on servicing one.

 

[johannielscom]

Looks good! Although the Jupiters are easy to work on, I'd suggest you use it for a bit first. It might just be stiff or sticky from being used too little for a long time and loosen up.


Should the need arise:

If you grip the front ring (in front of the aperture ring) and the focusing rear, you can just unscrew the whole optical unit from the focusing helicoid.

After that, mark the position of the three or four screws on the focusing collar (the one that has the distance scale on it) on the rear ring with the mount, and carefully unthread the screws. The distance scale now slides off and you can get to the helicoid easily.

I usually use cotton sticks to clean excess grease out, and get the grease out from narrow slots by using small pliers to cramp the cotton stick's end flat. Sometimes I apply a bit of lighter fluid to loosen grease up a bit.

Make sure you do not remove too much, the Jupiters had wide tolerances and in most cases the grease is also there to take up some slack in the parts. Let the lighter fluid evaporate and see if the action is to your liking, if not clean out more grease. I sometimes substitute with silicon lubricant, the right mix gets you a smooooth lens 😀

Work over a cloth to make sure your screws and such will not bounce off, never to be seen again. Ask me how I found out... :embarrassed:

 

[lxmike]

many many thanks for all the very good advice, help and link chaps, it is much appreciated

 

[goamules]

I bought two J-8s in a lot once. One was pretty stiff. I followed the guide on the web and easily had it fixed in less than an hour. I used some high temperature grease used on clothes dryers. Also, when you get it reassembled, you can really polish up these aluminum mounts to look like chrome!