Olympus Zuiko 200mm f5 Disassembly Question

[r_a_feldman]

I just got a OM-1 F-Zuiko 200mm f5 (not f4!) lens (serial number 120xxx) with a known fungus condition. The infection did not look too bad and the price was right.

I have been able to remove the rear two lens elements (behind the diaphragm) and the front element, but I am having trouble getting out the next two lens groups, the doublet and the plano-concave lens in front of the diaphragm. From the exploded parts diagram that is online it looks like the only thing holding the lens group in is a retaining ring which is about 1cm wide. It looks like the ring might have some thread lock applied, so I have been soaking it in acetone, without success so far (half a day).

Does anyone have any experience with this lens and any suggestions as to how to proceed?

 

[OAPOli]

Olympus lenses are notorious for their nasty threadlocker. Acetone is good but you might need a custom tool (i.e very rigid) for the retaining ting.

 

[ic-racer]

Try harder. (seriously)

 

[r_a_feldman]

Try harder. (seriously)

I did, and only succeeded in bending the tip of my spanner wrench.

Olympus lenses are notorious for their nasty threadlocker. Acetone is good but you might need a custom tool (i.e very rigid) for the retaining ting.

What I would like now is a pneumatic impact spanner wrench.

I am going to continue soaking the ring in acetone for several days more before I try again to loosen the ring.

 

[mshchem]

 

[r_a_feldman]

@mshchem,

Good one.

That is probably what I need, but I can get two good Zuiko 200mm f5 lenses for what it costs.

 

[mshchem]

Would warmth help? Warm acetone?? I had a old Japan made Leica screw mount 135mm lens that came in a box of stuff, the helical focus was absolutely " grease welded" I ended up throwing it in the trash. I tried everything. I think it would have required heating it to incandescent temperatures!

 

[OAPOli]

You can maybe find a hole saw of the right dimensions and grind two tabs. Those are hardened steel and would do the job.

I'm not sure what you mean by soaking in acetone, but watch out if this gets to the doublet. Acetone can dissolve lens cement.

 

[r_a_feldman]

You can maybe find a hole saw of the right dimensions and grind two tabs. Those are hardened steel and would do the job.

I'm not sure what you mean by soaking in acetone, but watch out if this gets to the doublet. Acetone can dissolve lens cement.

Thanks for the warning about the doublet.

I would need a hole saw with a 48mm OD, which is 3.5mm larger than 1.75 inches, so a hole saw is out. I usually use old hack saw blades cut and ground to the diameter of the ring if I need to fabricate a spanner. A hole saw will come in play though, in that I will use a 1.75" one to cut a 3/4" oak disk to mount the piece of hack saw blade (set in a slot across the disc). That is a project for tomorrow.

 

[OAPOli]

There are 1-7/8" ~ 48mm hole saws. A cylindrical tool will give you maximum rigidity.

 

[r_a_feldman]

This is what I made, using an old hacksaw blade, 3/4" oak, and a 3/8" bolt, epoxied together. No luck so far, using either a ViceGrip on the bolt or chucked into an electric drill, which gives an impact then stalls.

I will keep soaking the ring in acetone for a few more days...

 

[OAPOli]

Maybe you can show a photo of the ring? I'm not picturing the conundrum.

 

[mshchem]

Is it reverse thread???

 

[r_a_feldman]

Is it reverse thread???

No. It is a standard right-handed thread. That is one of the first things I check.

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@OAPOli: Here are pictures. The ring is part CB150300 in the exploded diagram from https://web.archive.org/web/20040807142114/http://olympus.dementia.org/Hardware/PDFs/200mm_f5.0.pdf.

WARNING: DO NOT go to olympus.dementia.org. Whoever owns the domain now is serving up malware -- a fake antivirus scam.

The ring is everything from the doublet lens element up to the threads at the top, so it is wider and more complex than the standard retaining ring. I have the CE191100 ring and lens LC60900 out.

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@Ian C: Thanks for the private comments. From the exploded diagram, there is not a set screw holding the ring in place. I have gotten some of the CRC brake cleaner fluid that contains tetrachloroethylene (reported to dissolve red LocTite) and am soaking the threads with it now.

Bob

 

[mshchem]

If it could be extremely carefully applied something that's a true penetrating oil? Or even a bit of methylene chloride (paint remover"

 

[r_a_feldman]

Progress!

After soaking the joint of the ring with the lens barrel with tetrachloroethylene brake cleaner for a day, I was able to turn the ring using my tool. It turns out that the ring is glued to a couple of tubes, so the remaining lens elements came out as a unit.

The ring A is glued to the cylinder B at line C. The rear cone D is glued to the cylinder at line E, Inside the cone is another retaining ring that holds the rear lens element in place.

Now I need to soak parts of the unit so I can disassemble it further (tomorrow, maybe).

 

[OAPOli]

Thanks for the update and good luck! For shame, Olympus.

 

[r_a_feldman]

SUCCESS!

After carefully soaking parts of the last assembly in the tetrachloroethylene brake cleaner (repeatedly applying it to the glue lines with a small artist's paintbrush), I was able to disassemble the unit. Now all of the lenses are free. I have treated them with hydrogen peroxide for the fungus and they all have cleaned up well.

@Ian C: Thanks for the brake cleaner suggestion. It does need to be used carefully and try to keep it away from the doublet, as @OAPOli recommended.