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Ben_hutcherson
Tinkerer
Username: Ben_hutcherson
Post Number: 19
Registered: 07-2006
Rating: N/A
Votes: 0 (Vote!) | | Posted on Tuesday, December 19, 2006 - 10:21 pm: | 
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I'm working on one of these for a friend. The lens was involved in an automobile accident several years, and this friend asked if I would take a look and see if I could do anything(it's already been written off and replaced, so he's not going to be upset if I mess something up).
Basically, when he sent it to me, the aperture wouldn't stop down at all, not even when dismounted from the camera(as would be normal for this mount type). I suspected an oily aperture. After playing with it some, though, I was able to get it to close down a stop, and found no evidence of oil on the blades. The lens now closes down one stop when dismounted. When the lens is set up as if mounted and focused from 10 feet to infinity, the stop down lever will cause the lens to go from wide open to down one stop, regardless of the aperture ring setting. When focused closer than 10 feet, the lens will close down one stop regardless of the stopdown lever.
I pulled the mount so that I could hopefully directly manipulate the aperture controls. Once I got inside it, though, I found that they were too deeply recessed to be able to do this.
Does anyone know where I might find a service manual or disassembly diagram so that I can pull the lens apart further?
Also, would anyone else have any suggestions as to what else may be causing the described problems?
I would appreciate any help.
Thanks,
Ben |
Glenn
Tinkerer
Username: Glenn
Post Number: 114
Registered: 07-2006
Rating: N/A
Votes: 0 (Vote!) | | Posted on Wednesday, December 20, 2006 - 08:11 pm: |
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Sounds like a classic case of the inner extensions, to the mount operating levers, not being located in the 'U' shaped brackets and/or cut-outs on the inner operating rings.
I suppose that a heavy blow to the lens could dislodge the inner levers. You can operate the inner operating rings by placing a long thin screwdriver tip in the 'U' shaped locators or cut-out. This will indicate if the internal mechanism is jammed.
If aperture is not jammed, the correct positioning of the inner levers in the 'U' or cut-out, will have the lens working again.
From memory, the manual is somewhat scant on the 300/5.6 FDn. Contact me direct if the above info does not correct problem, I will dig the microfiche out. |
Ben_hutcherson
Tinkerer
Username: Ben_hutcherson
Post Number: 20
Registered: 07-2006
Rating: N/A
Votes: 0 (Vote!) | | Posted on Wednesday, December 20, 2006 - 08:25 pm: |
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Glenn,
Thanks for the info.
I too suspected a heavy blow, considering that the lens was involved in a rollover and the owner doesn't have many details on what happened to it. He said that his AE-1 in the same bag was completely destroyed, so it's feasible that something did come loose in the lens.
Having just recently fixed my 135 f2 thanks to your advise, I pulled the mount hoping that I would be able to locate and operate the U-shaped levers as I had been able to when that lens was apart.
Even shining a bright light in, I'm still having a hard time locating the U shaped lever inside of the lens.
Can you provide any suggestions for further disassembly to locate the lever? In particular, it would help if there were some way to(temporarily) remove the two stiff pieces of flocking that are next to where the levers from the mount go into the lens.
Thanks,
Ben |
Glenn
Tinkerer
Username: Glenn
Post Number: 115
Registered: 07-2006
Rating: N/A
Votes: 0 (Vote!) | | Posted on Thursday, December 21, 2006 - 06:50 pm: |
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I have managed to find the details. Unfortunately they do not offer much help in the dis-assembly department. I will try and scan, however these normally turn out rubbish. I normally print out direct. If you send me your address, I will pop the 3 or 4 pages in the post.
The whole of the front lens group and housing can be removed from the rear section. Remove the large front rubber grip ring and then the two reinforcing semi-circular pieces, found underneath. The front housing is held by the axial screws that are revealed.
It would then appear that you can remove the internal focus group and then the aperture assembly. Aperture comes out from front, when the LOCATION SCREWS are removed. Remove the other revealed screws and you separate the front and back plates, hence loosing the blades. This is common to all FDn lens iris units. As I have never worked on this lens, I am going on the typical Canon exploded parts diagrams. The only dis-assembly instructions are details given above, for front group removal and complete stripdown of said group. there is a bit more on setting infinity focus on assembly.
Your two stiff pieces of flocking are a puzzle. I think this is what Canon call the internal light baffle. Only thing is, on the diagrams this appears to be a 'cone' shaped cylinder, with part of the side cut away. It seems to be attached under/to the aperture unit. I cannot see how this baffle is located/fastened from the info I have on hand. My understanding is, I have all the Canon published documentation on their tele lenses.
I will have a good look tomorrow and see if I can make more sense of the diagrams. The sequence of assembly is very clear, it is the fastening of the internals that is iffy. |
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