Topic: Zuiko 300mm f4.5 help needed.....

I have cleaned out my 300mm f4.5 Zuiko, which had contained some haze and dust. So far, so good.

However, there seems to be some looseness which allows movement of ~2mm between the part in front of and the part behind the aperture ring. I've taken some pics to show where the problem is to illustrate.

The looseness is between the aperture ring and the part to the right of it:
http://farm3.static.flickr.com/2002/3536906430_3c3ef582f4.jpg?v=0

As you can see, the lens is mostly apart at this stage, and though it is generally simple, taking apart or tightening this section is puzzling me. Does anyone have any experience in taking this section apart. I have two theories:
1) the front element set needs to be screwed off - I tried unscrewing it wearing rubber gloves after removing the three grub screws, but it does not seem to budge.
2) the aperture assembly needs to be removed to gain access to the screws that fasten the fron and back together

Here's a pic of the front:
http://farm3.static.flickr.com/2281/3536092075_3702edb115.jpg?v=0

Here's a pic of the rear:
http://farm3.static.flickr.com/2406/3536906056_d69514854f.jpg?v=0

Since neither seems simple to remove, I'd like to pause and ask for assistance! Perhaps I am missing something.

Any thoughts?

Thanks,

Last edited by robertro (2009-05-16 19:40:03)

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Re: Zuiko 300mm f4.5 help needed.....

So, I moved a bit further ahead. The two pieces were actually looser than I thought. By wiggling them for a while, I realized that two of the three screws holding them together were unscrewed, and the third was very loose. I continued to move the two loose parts until....drum roll....they came apart!

Great, so now I have the rear (aperture mechanism) off and clean, but it is now obvious that I need to get past the front elements to get to the screw heads to tighten the front assembly back onto the aperture assembly. As I said before, I had removed the three grub screws but the front won't budge.

http://farm3.static.flickr.com/2477/3538159566_c717bf5a60.jpg?v=0

1. line where I suspect the lens comes apart (BUT HOW??? TWIST??? HOW TO HOLD???)
2. where I removed grub screw: one of three visible
3. just a loose ring that holds the lens hood
4. where the aperture assembly (to the left of red line) was loose from the font lens assembly (right of red line)

I am suspecting that the front section is threaded on, and I have gripped both side with rubber gloves and twisted to no avail, so I'm going to sleep on it.

Your experienced input would be welcomed....

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Re: Zuiko 300mm f4.5 help needed.....

When I worked at Olympus in NY, I remember technicians putting a 300/4.5 in a vice and trying to unscrew the front lens group using a special wrench from Japan.  They broke the wrench off. "KUSO"  (Japanese for "sh*t").  Try dribbling some denatured alcohol into the space where the 2 screw together, make sure there aren't any hidden set screws.  With a wooden mallet, lightly tap around the outer casing  in line with where the threads are inside.  This may break them free.  Good luck.  I've had a few Zuikos freeze up on me like this, as if Olympuis had used some kind of loctite on the threads and over the years, it had really solidified.  John, www.zuiko.com

OM Service since 1977
21 South Lane, Huntington NY 11743
631-424-2121

Re: Zuiko 300mm f4.5 help needed.....

Thank you for your response - it confirms that the front unit does screw off and that it is a challenge!

I will try the alcohol in the threads; someone else had suggested WD-40 (I assume for the kerosene content). I have checked carefully for set screws; there appear to be none beyond the three I've already removed.

The wooden mallet is scary, but makes sense I'll proceed carefully on this.

The loctite theory makes sense; too bad that Oly didn't put loctite on the three bolts that loosened up. But then, I wouldn't be having this fun, would I?

Thanks again for sharing your valuable experience. I'll report back on the weekend!

Robert

Last edited by robertro (2009-05-20 17:56:09)

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Re: Zuiko 300mm f4.5 help needed.....

Robertro,

I have only just recently obtained one of these lenses (fortunately in excellent condition- as far as I can tell, so far).  I am still waiting for my first two films past it to return from the processors- due back tomorrow- so I can see if it really is OK or not.

I have been very interested in your saga regarding this lens.  I'll let you know how mine worked out as soon as I have the results. smile

Re: Zuiko 300mm f4.5 help needed.....

Robertro,
  Try to get a couple of strap wrenches. They are normally used for removing oil filters in cars - here in the UK the car sized one is called a 'Boa Constrictor wrench'. I then found smaller ones, called 'Baby Boas' and have two of them. So far, eventually, nothing has been able to resist them. As omtech1 said. soak well in alcohol.

  I believe the small ones are also sold in cookshops for opening jars with stuck lids.

Regards

Angus

Re: Zuiko 300mm f4.5 help needed.....

photomac wrote:

Robertro,
   As omtech1 said. soak well in alcohol.
Angus

This applies to the operator as well as to the lens? smile

Re: Zuiko 300mm f4.5 help needed.....

Banjo
  "This applies to the operator as well as to the lens?"

   Definitely, although it is crucial to use the correct grade. The superior version for human consumption has too much peat in it for less capable mechanical devices to accommodate big_smile

Regards

Angus

Re: Zuiko 300mm f4.5 help needed.....

Well, the weekend is coming, so I'll have to do some shopping tonight to get ready to tackle this stubborn lens by picking up the appropriate strap wrenches and alcohol.

Let's see - is that a single stop at the hardware store, or does it require a second stop? Anyone with experience is welcome to comment!

Last edited by robertro (2009-05-24 01:30:26)

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Re: Zuiko 300mm f4.5 help needed.....

After leaving WD-40 on the seam where the threads were locked for what seemed like days, I bought two strap wrenches today and.....IT WORKED !

With a minimal amount of force on the strap wrenches, the front lens element assembly released and threaded off as if it had always been loose.

The lens is in great shape after lightly cleaning the optics and aperture, and the body is like new, so if I can remember how to re-assemble it, I'll have a beauty.

Last edited by robertro (2009-05-24 01:30:57)

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Re: Zuiko 300mm f4.5 help needed.....

robertro wrote:

Well, the weekend is coming, so I'll have to do some shopping tonight to get ready to tackle this stubborn lens by picking up the appropriate strap wrenches and alcohol.

Let's see - is that a single stop at the hardware store, or does it require a second stop? Anyone with experience is welcome to comment!

That should be two stops: hardware store and bottle shop smile.

Re: Zuiko 300mm f4.5 help needed.....

Well, I did have a little celebration after getting the lens apart.

Now, I have it almost back together - working in 15-minute efforts between playing with/reading to my 4 and 6 year olds. The front focusing mechanism is all that is left and this will require some experimentation to get the correct focus - although I marked the front an back sides with tape, my piece of tape fell off the center piece.

Close!

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Re: Zuiko 300mm f4.5 help needed.....

I did it. The helicoid was interesting to get back together again, but I did it, with perfect infinity focus, after some experimentation.

The focus is a bit stiffer than I would like, but I hope that works itself out, since I don't really want to take it back apart any time soon.

I took a few snaps, and it's a sharp lens, and relatively easy to focus. The focus confirm chip on my dslr works well with this lens.

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Re: Zuiko 300mm f4.5 help needed.....

Good job Robertro! Now you'll want to do lots of lenses!

To avoid the problem of the tape falling off (been there, done that) I use correction fluid (Snopake, Tippex, White-out) to put alignment marks on components. It wipes off easily with alcohol when you're finished.

Regards

Angus

Re: Zuiko 300mm f4.5 help needed.....

Brilliant!

Where were you when I began ;-)

Robert

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Re: Zuiko 300mm f4.5 help needed.....

To all that helped out - I have posted one image from the Zuiko (in a comparison with a Soligor lens) in another thread. Though the Soligor is not a bad lens and a bit more compact, the Zuiko wins hands down.

http://forum.manualfocus.org/viewtopic.php?id=14322

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Re: Zuiko 300mm f4.5 help needed.....

Old thread, but if anyone is looking for the photos of the lens parts, they are now here:
http://www.flickr.com/photos/robertro/s … 424681445/

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