Looking inside a 6X7 200mm for a loose screw.

A question from "Mike"...

 Inside a 67 200mm f4.0... sad thing is that I don't have one yet... however, we can at least get an idea of how it works.



First is the protection and work area:
Nice clear table and don't do what I tend due to tight table space, give yourself around 10 to 12 inches of edge to reduce the screw loss.  Work on a solid table.  set aside some screw organizing spaces (lids, trays, ice cube tray...). Work on a large sheet of paper and have a pen/pencil handy.  Whenever possible, put caps or filters on elements while working or go as far as making temporary lids to protect element in case a tool snaps and sends you crashing in a bad direction.



Screws can be a pain:
Working with the rear element is hard to do on a lens that has not been open since it left the factory.  In summer season the screws seem a little tighter... maybe it is me.  I have an odd technique to start and it is to carefully tighten a little when I encounter a tight screw... Not to say to rock it from tight to loose and back!  That will get you a snapped screw.  Another thing is a little heat from the business end of a soldering iron.  I would head up the screw and area for a bit and wait for it to cool slowly and try again, but this I use as a last resort


Second is the tools themselves:
I have a combination of Moody drivers and Wiha drivers.  The Moody version I have are the cheap plastic by reasonably strong and they do have a more pricey set in all metal.  The Wiha is a flip change version and is a little stronger although plastic.


Third is to try and ease screws loose first before removal...

 
yes... I'm being a little careless waving a tool around near the glass.

here is the removal of the 3 screws and the clearing of the aperture armature.  As shown is the gingerly wiggle to clear it off.

I chucked part 2 as it was too long and redundant...

next is the mount...




well, I'll almost have it off when the flange is out of the way.

IMPORTANT: One the mount is off, try not to lift up the ring.  You may disconnect more than you want on some versions.


next, where it rattles...


A note about 'Loctite' or alike is that it is applied to the thread however in all the examples for this area that I've found, it is applied to the top much as with the flange and so the preparation to apply is more time consuming.

Inside is:

1 mounting screw or post for the spring

2 screw to secure the lever, but one has double duty to hold the return spring in place and the other is just for the lever.

1 Pivot screw as in my example of a slotted screw.  Commonly does come loose over time.


Once the screw is sorted out is the little attention to details to put it all back together.


...next... putting it back together.

Mentioned was this little arm.


So you simply align the mount first to were it must be tightened back and don't forget the little flange that stick out through the mount.


You will see the lever operates the arm inside that is what lifts the 'MAN' mode lever up.




So as you lower the mount make sure the little arm rest on top the lever inside.  When the mount is resting back in place, test to see if the lever and arm work.

On the shroud is the armature to mate with the aperture lever.














Here is a shot of the lever rod.  You'll have to sight through the tight confines of the lens to match them up, but that is the only big task left.  Once the shroud is seated, you can test to see if the aperture is working.  Just the three screws and your good.