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SAL70200G repair question

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Alfasud1972 View Drop Down
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Joined: 01 September 2016
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Post Options Post Options   Quote Alfasud1972 Quote  Post ReplyReply Direct Link To This Post Topic: SAL70200G repair question
    Posted: 18 November 2021 at 11:53
While taking the first three front lens elements out of my SAL70200G (to remove some dust) four rings fell out of the barrel (i think: WASHER (FOCUS POINT MOVEMENT ADJUSTMENT WASHER), one thin aluminium one, one thin copper one, and two slightly thicker aluminium ones.

In which sequence should these be put back? The repair manual that I have is of no use as far as I can see.

Kind regards,

Rody

Edited by Alfasud1972 - 18 November 2021 at 11:59
 



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MinoltaMad View Drop Down
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Post Options Post Options   Quote MinoltaMad Quote  Post ReplyReply Direct Link To This Post Posted: 25 November 2021 at 05:47
Hey Rody,

What a pickle. The Sony service manuals are never detailed enough on these little aspects - they tend to only show a group of washes without any distinguishing features. My quick advice is that they probably don't matter on order - if they go as a group clustered together one on top of each other it is all about the size or depth. From details I could find there were a range of different sized washes they used for this lens and depending on what it needed tweaked the combos. I have a G2 version and have never needed to take it apart - no dust or anything inside it so far.

My closest experience is taking apart the Sony 70-400mm G1 and G2 versions which have a slightly different arrangement with the front element. My G1 version has about 8 brass full circle washers (similar to what you're describing but all the same width and type) and then at two of the three main screw mounts - has additional sets of smaller shim (only for that screw position) brass washers. I was really fortunate when I first dismantled the G1 version to see where they all spilled from (I'd also used a black marker pen to mark the sides of all the washers so I knew exactly which way they went back in). Now my G2 version has way fewer of the washers and none of the little shim ones. All of these are to do a final focus correction and probably are bespoke lens to lens or they might work for the majority and could be what some folks describe their copies to be better or worse. With the 70-400mm lenses - there is a handy trick that is never mentioned anywhere - there are 6 small screws holding in the front element block - you remove all of them, then gently replace three that don't fully hold the front element block in place - you can then remove the front element fully and all of the washers stay in place without the spill.

Sorry it wasn't a direct help - as I indicated I'd put it back together and see how it takes images. If the focus seems funky, work out a trial and error pattern of taking it apart and switching the order up of the washers until it is working how you want it to.

Folks get worked up about the internal elements not being hardened and coated - to be really careful if you're worried about cleaning - use the highest quality 100% isopropyl alcohol and the high end microscope cleaning tissues. Roll the tissue into a cigar like fashion and wet it with the isopropyl and pull it fully across the surface - repeat etc. The only thing to watch with too much fluid or solvents when cleaning from the inside of the element - is if it gets into the cement gluing the elements together. The solvents can degrade the cement over time if there is a way in or imperfections. One of the 70-400's took ages to clean because the lubricants inside had dispersed a volatile film off the grease over the inside of the element, but a bit of patience got it off.

Best of luck
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