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Wjc
Tinkerer
Username: Wjc
Post Number: 1
Registered: 07-2009
Rating: N/A
Votes: 0 (Vote!) | | Posted on Friday, July 17, 2009 - 02:43 am: | 
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Hi -
I am trying to repair the iris on a Tamron twin tele 1:2.8 135mm manual lens, where the blades have become jammed.
I have removed two lenses from the front, but access to the iris is blocked by another lens. This is also the case from the rear. Neither or these lenses seems to want to come out.
The lens at the rear has a screw ring keeping it in, and when the ring is removed the lens protrudes from the surrounding housing - but it won't shift.
The lens at the front sits behind two front lenses and does not protrude from its housing - but there seems no further retaining rings to unscrew.
I have searched for any grub screws along the barrel and removed them (two roughly fore and aft of the iris position), but nothing else comes apart apparently.
What am I missing ?? Are lenses glued in position ?
Thanks in advance for any advice
Simon |
Wjc
Tinkerer
Username: Wjc
Post Number: 2
Registered: 07-2009
Rating: N/A
Votes: 0 (Vote!) | | Posted on Sunday, July 19, 2009 - 02:58 pm: |
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Update - problem solved. With a bit of a tug the front ring comprising the lens assembly holding the two lenses mentioned unscrews from the barrel. So no need to have taken them out, duh.
After that loosening the top grub screw enables a retaining ring to be unscrewed, a third lens taken out of the barrel leaving access to the iris assembly.
The iris assembly comprises a top ring with slots in, 12 petals with pins enaging in the top ring and also into holes in a bottom ring. The bottom grub screw mentioned above secures the bottom iris ring in position.
The iris assembly comes out, but putting it back together taxes one's patience(locating the 12 petals sandwiched between the top and bottom ring is like making a house of cards - slightest twitch and all the parts pop out. Nothing holds the various parts together).
The trick to putting the iris assembly back in the barrel is to carfeully place the assembly front side down over a mandrel, hoping all the parts stay engaged, then slip the lens barrel down over the top.
After that everything goes back in the way it came out.
Hope this helps anyone with a similar problem.
Simon |
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