Topic: Tamron 300mm SP aperture fixing

Trying to get this going again, it went suddenly working then not. here an overall
http://farm1.static.flickr.com/156/367379639_4b36a25639.jpg


from what I can make out moving the aperture ring moves cam A (Red)
which moves part B (yellow) backwards and forwards
that movement Should be  transfered to the aperture by lever C (Blue)

http://farm1.static.flickr.com/177/367379478_72c1479cd1.jpg

at the bottom of lever C (tricky shot!) some how is suposed to move the brass bit to open and close the aperture

http://farm1.static.flickr.com/136/367394061_f567548926.jpg

neither the top end of lever C is getting moved by rotating the aperture ring, nor if I move it manually is the other end connected to the brass aperture actuator

Any ideas? It'd be a shame to loose this one.

bigger pictures here
http://www.flickr.com/photos/hacksawbob … 431297686/

Re: Tamron 300mm SP aperture fixing

Will the top lever move the bottom lever if you do it manually in this state?
If you can move it by hand, can you feel any restrictions?
And, did any parts fall out when you disassembled?

(just questions that are part of my trouble-shooting sequence)

Seymore
MooreFoto

Re: Tamron 300mm SP aperture fixing

No parts lost as far as I can see. I think I have established that the problem lies with the ring in which the aperture blades sit is loose, The post with the spring in the last picture  needs to be held against the bottom of the lever C But I cant work out how this is done, maybe a loose grub screw somewhere. Not sure if I want to strip it any further, there are some tricky bits to dis-assemble to go any further.

Re: Tamron 300mm SP aperture fixing

Ahhhhhh... I think I see what you're saying here. Ok. Well, no specific experience with this lens. And I suspect that often specific tools were used to assemble lenses correctly. So, without something like this, you may have a hard time getting things back together. Took another look @ the assembly PICs... Looks tricky.

Don't know that I can assist any further. )o: Good luck...

Last edited by Seymore (2007-01-24 00:46:20)

Seymore
MooreFoto

Re: Tamron 300mm SP aperture fixing

Drop forum member 'Tamron Sp' a begging note. He is a nice fella and can take these apart in hs sleep.

Re: Tamron 300mm SP aperture fixing

was hoping he would be a long at some stage, maybe I can give him a nudge. I have been taking it apart in my sleep too, but more like a  nightmare for me! smile

Re: Tamron 300mm SP aperture fixing

I would have thought that the top of lever C should be on the other side of that pawl that has the large spring, I presume this pawl is controlled by the Auto/Manual switch. Where it is at the moment looks as though it will just hold the diaphragm in the fully stopped down position.

Ramon

Statistically, 6 out of 7 dwarves are not Happy.

Re: Tamron 300mm SP aperture fixing

So try and move the post under lever C? may need some "persuasion"

Re: Tamron 300mm SP aperture fixing

hacksawbob wrote:

from what I can make out moving the aperture ring moves cam A (Red)
which moves part B (yellow) backwards and forwards
that movement Should be  transfered to the aperture by lever C (Blue)

at the bottom of lever C (tricky shot!) some how is suposed to move the brass bit to open and close the aperture

neither the top end of lever C is getting moved by rotating the aperture ring, nor if I move it manually is the other end connected to the brass aperture actuator

Any ideas? It'd be a shame to loose this one.

Hi hacksawbob,

http://farm1.static.flickr.com/177/367379478_72c1479cd1.jpg

Rotating the aperture ring indeed rotates the cam ring A which then moves the aperture mechanism B back and forth. The aperture actuator mechanism C is a totally separate mechanism from A and B. The tiny brass bit at the bottom of C is just the visible portion of a larger rotating part which isn't in direct contact with the lever C.

The aperture mechanisms within these older Tamron lenses are not subject to failure due to broken or loose parts. Instead it appears that internal dust building up on a fine oil film on some of the aperture assembly's parts has gummed up the aperture to make it stick from time to time. Further disassembly of the rear of the lens is required, yet it isn't very difficult on this model once you know what to do.

I am really busy at work and some CLAs, but will post some photos and instructions for you in a day or two. You will have the aperture working and the interior of the lens nice and clean in no time! Just be patient for a day or so.

--Michael

Visit Adaptall-2.com for information about vintage Tamron manual focus lenses.

Re: Tamron 300mm SP aperture fixing

Thanks Micheal, when you've got a minute. Its all tucked up in a tuppaware box. I cant see how the aperture movement makes it to the aperture, I look forward to your picks. Just on a side note the engineering in these thigs is amazing, the machining on the block of metal that sits under the part B is something to behold, whats it made from? must be some kind of alloy, a bit of steel that chunky would really weigh the lens down.

Last edited by hacksawbob (2007-01-26 08:58:06)