Well, a good ending to this story... I took apart the lens and found 2 of the pins had worked their way loose. The loosest one was just barely haning on with a couple of threads. I ended up taking everything off, except for the apature and lens assemblies on either side. It was a puzzle and after completing it, I checked infinity and looks good. There is just the slightest bit of wiggle in the focus/front assembly, but that's because I didn't have new pins/nylon washers to install. I simply moved them all to different spots and eliminated most if not all the wiggle. Very usable now. About half way through, I relaized that the job could have been done without taking the back mount off, and could have fixed it from the front end and middle/outside.
Steps:
Start by extending lens all the way out, and take a picture of the lens so you can see all the markings for lining up them again later.
1. Remove focus grip.
2. Remove tape under grip.
3. Unscrew top focus ring counter clockwise.
4. Remove 3 screws and lift out metal washer plate.
5. Lift up and off the lower focus ring, carefull not to turn front element.
6. Mark the side of front element's metal mount and side of tube with a horzontal and vertical scribe giving both correct depth and alignment of front lens assembly for re-install.
7. Unscrew the front lens assembly counter clockwise and remove. (Opptional) You can leave this in if you want, but you may damage glass. Up to you.
8. Remove zoom rubber grip.
9. Remove the two silver slotted screws.
10. Turn the zoom ring and look inside of the other holes as you turn to find the black philips head screws. With one lined up, the others will also be lined up with holes. Remove these screws and the plastic tube with the colored lines on it should now be free to slide up and off.
11. Slide the plastic tube that the these screws were holding up and off the lens.
12. At this point, you'll see the zoom guide pins. Check for looseness and tighten, and if still too much play, move them different positons.
13. Reassemble in reverse order.
14. Check that your marks line up, and if not remove and try a differnt starting point, and repeat until marks line up. It helps to have another mark on the ouside of the tube just at the point there one of the groves of the threads exits, so you can match up the begining of one thread on the lens assembly to that mark with starting to thread the assembly in. Take your time and when you place the assembly down onto the lens tube, turn it backwards first until you feel the assemble drop down every so slightly into the threads, and then try to move it forward (clockwise) gently and see if it will start. It take some practice and some time to get the feel for it. It's not like screwing on a nut to a tappered headed bolt, more like starting a nut on a freshly cut piece of threaded rod. It can be done, but it take time to find just the right spot to get it started.
15. Once the marks line up for both height and rotation, do not move the assembly when putting the lower focus ring back on with it lined up at infinity.
16. You may have to rotate the zoom ring, as I put my silver pins/screw in the oppisite holes the first time. Just take them out and turn it 180 deg and install again.
Note: Cleaning the lenses is a good idea. I used a LensPen(TM), and a rocket blower to keep the dust down.
Let me know it this helps anyone, or if I missed something, as I'm writing this from memory and revised it to eliminate my wanderings.
Craig
