Several years ago, when I was shooting Canon, I got a hold of a 17-85 lens with a jammed zoom. Turns out this was a relatively common problem caused by a loose screw. I found
an online guide posted by someone else who'd done the repair, so I gave it a shot. I disassembled carefully, taping the screws down on the printed pages from the online guide corresponding to the stage of dismantling at which they were removed. The problem was as advertised. I replaced the loose screw that was the culprit and got everything back together again. I put on the camera turned it on, and by golly it worked! So I ended up with a $500-$600 lens for free. I got a bit of use out of it on my 20D before it fell victim to a
second common malady to which this lens was prone:
failure of the ribbon cable controling the aperture mechanism. There were
tutorials and guides for this fix too, but it would require a higher degree of disassembly and the purchase of a replacement part. I thought about doing it myself, but decided not to. The second failure for this lens, combined with the loss of AF on the Canon 18-55 kit lens (also ribbon cable fatigue failure) left me essentially camera-less and in the market for a replacement. I tried out a 70D, and it was good, but beyond my budget at the time. It was while I was in this state of affairs that I was able to borrow a Pentax K-S2. I even already had an A 50mm f1.7 that I hadn't used much on my Canon (I had adapters for K-EOS and M-42 to EOS). I
t was an out of focus self-portrait with this lens on the K-S2 that sold me on Pentax. I jumped ship and dumped Canon.
Can't say I would try this on something that wasn't a) free and b) already dead, though while I was still shooting Canon, I did remove the minolta mount on my Tokina 500mm f8 mirror to M42. Dead simple. No aperture linkage. It worked too.
Camera though? Nope.