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[OM] Re: 28mm f/2.8 repair advice

Subject: [OM] Re: 28mm f/2.8 repair advice
From: John Hermanson <omtech1@xxxxxxxxxxx>
Date: Thu, 30 Nov 2006 08:23:36 -0500
The pin on the 28 2.8 is L shaped and connects to the diaphragm control 
cam through a slot in the main tube.  To remove the ring, you'll have to 
take out the 2 screws holding the pin in.  Unscrewing the front lens 
assembly, which would expose the diaphragm mechanism, should reveal what 
the problem is.

___________________________________
John Hermanson
Camtech Photo Services, Inc.
21 South Lane, Huntington NY 11743
631-424-2121 | Olympus OM Service since 1977
http://www.zuiko.com  |  omtech1 AT verizon.net


Chuck Norcutt wrote:
> Hey, here's a real, live, nitty-gritty, on-topic OM post!
> 
> I have a 28mm 2.8 which will not open (using the diaphragm ring) to more 
> than f/5.6.  The diaphragm blades open fully when the DOF preview button 
> is not depressed but the diaphragm ring can't be rotated to either f/4 
> or f/2.8.  It hits a hard stop at f/5.6.
> 
> I assumed that there must be a problem with the detent ball but was 
> surprised when I removed the filter/detent ring and found that the 
> detent mechanism is fine and there is no appreciable wear on the ring.
> 
> I tried rotating the diaphragm ring again without the detent ring and 
> ball installed and it still hits a hard stop at f/5.6.  Then I tried to 
> lift off the diaphragm ring and was surprised to discover that I 
> couldn't.  I can lift the side opposite what I'll call the diaphragm 
> coupling pin (CE157300 on the parts diagram) but that pin acts like it 
> has a hook on the end.  The pin side lifts no more than 1/2mm and stops 
> cold just as though what I think should be a flat bladed pin has a hook 
> on the end and is catching on something.
> 
> Any suggestions?  If I remove the lens mount will I be able to see the 
> inside of the barrel and figure out what the obstruction is?  I guess I 
> could also remove the two screws attaching the diaphragm ring to the 
> coupling pin but I hate to disassemble what I don't have to.
> 
> Thanks,
> Chuck Norcutt
> 
> 
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