TurbosLS1ta Offline Upload & Sell: Off
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Ok, so here is probably the most in depth write up Ive ever done, so bear with me.
Some tools you will want are a small pick, small flat blade screw driver, PZ0 (or sunglass kit) philips screwdriver, needle nose pliers, loctite, flashlight (or headlamp, or a very well lit room), can of compressed air.
Here is the culprit lens, a Sigma 24-70 f/2.8 EX DG. I cant imagine the majority of lenses being much dissimilar in the process, but they may be, so this is meant to serve as a general guide. Once your eyes have fallen upon this write-up, I am no longer responsible for your screw-ups or voided warranty, etc whilst you commence tearing down your own lens.
I figure what happened is the previous owner dropped in (just missing the objective lens, luckily) which shatter the plastic washers in the zoom tracks (forgive my lack of a technical term) inside the camera. The front barrel was loose from the rest of the body, but surprisingly took sharp pictures up until the 70mm range.
So the first step is to remove the four (4) stainless screws from the mounting plate.
BEFORE you remove the mounting plate, you must disconnect the power ribbon connected to the circuit board underneath. BE EXTREMELY CAREFUL, as these ribbons tear easily. Never force or pull them hard.
To disconnect the ribbon, you will need a small flat blade screwdriver or pick to push the black tabs open. This one is tricky as you will have to be careful when holding the mounting plate and trying to disconnect the ribbon at the same time. As you can see, there is not alot of room to do it. The red arrows indicate the tabs to press, and the blue arrow indicates the direction to push them to unlock them. This pic shows the connector unlocked.
Once you have the mounting plate removed, you will have to remove the brass spacers. There are several of them in various thicknesses. Im not sure if their order is important, however notice the pinhole orientation 180* from the power ribbon connector.
When the spacers are removed, you will see three (3) counter sunk screws. Remove them.
Once the screws are removed, I advise moving the focus switch to the Manual (M) position. This moves the switch pawl up, making it easier to slide off the gear during removing and re-installing the focus switch ring.
Once the focus switch ring is off, you have better access to the circuit board. Remove all the ribbons from their connectors the same way you removed the first ribbon. Once they are out, remove the one screw holding the circuit board to the body (be careful, its a tiny screw).
The circuit board is connected to the focus motor via a red and black wire, so just let it dangle to the side while you remove the three screws holding the focus motor/gearbox on.
Remove the focus gear and spring, noticing the gear orientation.
Next remove the two screws holding the ribbon to the body. Place a finger where the blue arrow indicates, as removing the screw can twist the ribbon, possibly tearing it.
Remove the rubber grip band from the zoom ring. Under it you will notice a single screw. Remove it, and be careful as it can fall into the body.
Once the zoom ring screw is removed, look right inside the zoom ring and you will notice it is indexed to the internal body. DO NOT ROTATE THE ZOOM RING MORE THAN 90*! Doing so will damage the electronic "fingers" inside the ring used to locate what zoom range the lens is at. When the ring is indexed properly, it will come off.
The "fingers" ride along this ribbon, so the camera can figure out what focus/zoom range the lens is at.
Once the zoom ring is off, remove the three screws shown to disconnect the internal elements from the outer body.
Once those screws are removed, the outer body should just slide right off. In the case of my lens, the zoom ring tab had come loose from the internal element, making it difficult to remove. If this happens, dont force it- just wiggle and work it a little and it will come.
Viola
These are the screws that had the plastic washers that were broken, causes the loose objective barrel. All I could find locally were some #4 nuts. The fit over the screws perfectly and all I had to do was file the hex down to make the nuts round. Once I can find the proper parts, I will replace them, however I am like most photographers and cant live without my equipment for long.
If you need to disassemble any further than this, then you have some serious problems I may not be able to help with (cracked glass is about it).
Re-assembly is pretty much the exact opposite of disassembly. Again, just be very careful of the ribbons. I was fortunate that the ones in this lens were in good shape, but old, aged lens will have very brittle ribbons. As for the can of compressed air- use it alot during assembly. Dust WILL get into the lens while it is apart. If not, any dust that is already in the lens willc ome out, making your photos even better than before..
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