150mm F2.8 EX DG OS HSM APO Macro - dysfunctional

[stenrasmussen]

Another project came in.
Said lens suffers from loose brass collar/nut that currently lives a life rolling around on the aperture blades. Suffice to say the lens inoperable and my task is to try and fix it.
If anyone has a diagram or service chart/manual to share it would make my life easier. I will however get going and hopefully I can get to the bottom of the problem. Will post pics and updates here in due course.

[richardHaw]

currently looking for a guide. looks like there are non available even on japanese sites 
i will tell you once I saw something

[stenrasmussen]

currently looking for a guide. looks like there are non available even on japanese sites 
i will tell you once I saw something

Much appreciated 

[Bjørn Rørslett]

In addition to your extensive Lens Medical Studies, you might have to learn Japanese, Sten

[richardHaw]

i can write to sigma and request a repair guide. night worth a try 

[stenrasmussen]

In addition to your extensive Lens Medical Studies, you might have to learn Japanese, Sten

I am like a toddler...just looks at pictures and pretend I can read 

[stenrasmussen]

i can write to sigma and request a repair guide. night worth a try 

THAT would be an interesting exercise!

[stenrasmussen]

So the little brass-fecker has been found, as has its securing screw. I am hugely impressed by the build quality of this Sigma. Metal and such does not stand back related to Nikkors (real Nikkors).
Here are a few pics showing the process. The lens needs to be assembled again and I'll report back with end result.

[richardHaw]

that looks stupid, how did that cam roller get off it's thread 
maybe somebody forgot to use threadlock 

[stenrasmussen]

that looks stupid, how did that cam roller get off it's thread 
maybe somebody forgot to use threadlock 

That's the thing - I couldn't spot any remnants of threadlock stuff on the screw. Also, there's only ¼ of the screw length holding back the leverage from the remainder ¾ of the screw.

[Erik Lund]

Don't over-tighten that screw!

3 threads in is not enough for such tiny threads, normal design says depth of threads must be at least 1.5 x the diameter,,,

Maybe the lens was dropped, that's the usual case for these to break or loosen,,,

[stenrasmussen]

Don't over-tighten that screw!

3 threads in is not enough for such tiny threads, normal design says depth of threads must be at least 1.5 x the diameter,,,

Maybe the lens was dropped, that's the usual case for these to break or loosen,,,

I know Erik, the lessons learned from previous overtightened screws have taught me to add just enough torque on the JIS.
A drop situation might very well be the cause.

[richardHaw]

or maybe vibration (car/train/plane) 
no thread locks whatsoever!

[stenrasmussen]

I am happy to report that the lens is back in working order!
No threadlock added as I opted to return the lens as was - sans the dust between the lens elements and those loose parts 
A couple of tips:
- There is a long thin flex cable that is best fastened before the circuit board is secured in place with the two screws (see pic below).
- There is a difference to the four screws securing the rear light baffle and contact block. The two going into the metal of the contact block has finer threads than the other two with coarser threads that goes into the plastic light baffle (pic below).
A couple of pics showing how I do the job with the flex cables added as well.

[Erik Lund]

Well done Sten!

No need to remove dust in lenses, doesn't matter since the image is not formed inside the lens, for ultra wide angle lenses a clean front element is mandatory and for most lenses a clean rear element is required.

I just love the reference with two different types of screws in the light baffle  - There are so many different screws all over that lens your not supposed to mix up