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Minolta 100 2.8 macro cleaning & TC issue

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ffrolvaag View Drop Down
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Post Options Post Options   Quote ffrolvaag Quote  Post ReplyReply Direct Link To This Post Posted: 11 January 2019 at 12:42
Yeah, the real difficulty in reassembly of the lenses is getting all of the barrels to line up correctly. The reason I tore down my first copy is I bought it cheap, but there was a large piece of brown paper that had made its way into the optical pathway. As a result, it did effect the images. However, most of the time, dust needs to be pretty large to impact images.

Most stiff focus issues are related to one of two likely scenarios.

First, it would be one or more loose screws or a damaged bushing around the screw head in the concentric barrels. At least one of my copies had one that had completely backed out, and would sometimes jam. You will observe this both in MF and AF, so switch to MF and see how bad it is at different speeds.

Second, there can be debris that may get bound between the gears. One of my copies was purchased very cheap, but was physically and optically near 100%. However, the previous owner had clearly given it a particularly nasty sand bath. While it didnít damage the optics, the sand was everywhere and bound movement of the barrels while making loud crunching sounds. That was a fun cleaning job . . .
Franz



a900, a700, 5600hs, 1200 (w/MFC-1000), 3x converted f1.2 (Rokkor 58, Nikon 50 ais, and Pentax 50), 85mm f1.4, 100mm f2.8, 70-400G, and way too much other stuff to mention
 



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ffrolvaag View Drop Down
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Post Options Post Options   Quote ffrolvaag Quote  Post ReplyReply Direct Link To This Post Posted: 11 January 2019 at 12:46
Oh, one more thing. If you do decide to tear the whole thing apart, take lots of pictures, and label each of the screws on the screw and the barrel. Take lots of pictures of the location and position of both. This will really aid in reassembly of the barrels since there will be lots of slots and holes that need to be aligned. Hopefully you donít need to do it though. The 50mm and 100mm macros lenses are likely the sharpest lenses Minolta made, and if not, certainly in the top 10.
Franz



a900, a700, 5600hs, 1200 (w/MFC-1000), 3x converted f1.2 (Rokkor 58, Nikon 50 ais, and Pentax 50), 85mm f1.4, 100mm f2.8, 70-400G, and way too much other stuff to mention
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sakisf View Drop Down
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Post Options Post Options   Quote sakisf Quote  Post ReplyReply Direct Link To This Post Posted: 13 January 2019 at 20:01
Originally posted by jackal2008 jackal2008 wrote:

My copy of 100 macro would stuck some time. Wondering how difficult it is to just lubricate focus part. If you have some photos, would you mind sharing a bit? Thanks.


I am sorry I only took very few photos of the disassembly as it was pretty easy to do for this lens.

Here is what was wrong in mine, gears had dirt, the teeth there on the outside barrel too, two of the three screws needed tightening on the outside barrel and the old grease (I typed grass in the screenshot!) in the grooves was dry:




There is no need to completely remove the screws in the grooves if you do not need to disassemble further, just remove one, clean it, put it back, move on to the next. Red lines are where I put lubricant - outside surface of inner barrel & sides of grooves in the external barrel where the screws touch on -, don't put directly, apply with the head of a cotton swab or absorbent kitchen paper towels which does not leave fibers.

Edited by sakisf - 13 January 2019 at 20:09
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Post Options Post Options   Quote jackal2008 Quote  Post ReplyReply Direct Link To This Post Posted: 14 January 2019 at 20:22
great! i'll try to clean it while kids are away :) thanks a lot for sharing.
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