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How to repair/restore manual focus functionality to old Minolta AF 24-105mm lens

Colin O

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I have an old Minolta AF lens - 24-105mm - which continues to function, except for one thing - manual focus is a bit off. What I'd like to do is understand how it should work, and see if I could maybe give a DIY repair a go.

Here's an image of the lens:


The lens is obviously zoomed out to 105mm here. You can see two rubber rings on the lens - the one closer to the mount controls the zoom, while the other one is the focus ring - which is the one giving me trouble.

Basically, when I turn the manual focus ring lightly, it has no effect - it just spins freely. If I grip the ring very strongly, then it works as intended. I'm wondering what has gone wrong in my lens - how is this rubber ring physically connected to the manual focus mechanism underneath? Is it purely based on friction/inertia, or something more complex? Maybe the rubber ring in my case has simply lost some of its elasticity/tightness over time, and manual focus functionality could be restored simply by adding some adhesive underneath the rubber ring (to ensure that when it is spinned, it also spins the barrel underneath).

Alternatively, maybe the MF mechanism is more complex than that - is anyone familiar? I'm hoping though that whatever it is, it could still be fixable by me performing some not-too-complicated DIY job.

Final relevant point... when Sony entered the DSLR market, they introduced some lenses that were 100% clones of Minolta lenses, but with Sony labelling; the 24-105mm was one such lens - and I've been able to find the Sony service manual for the lens: https://allphotolenses.com/public/files/pdfs/10dcbbbf73c848d4f5ec340dcbd1abdf.pdf

While I've looked through its diagrams of course, my issue still wasn't clear to me, but maybe someone else can interpret the service manual better than me.

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