Tamron SP 35-80 Aperture not activating

[Zuikopath]

I wonder if anyone can shed some light on this problem - I have removed the Adaptall mount from the lens and unscrewed the three screws that hold the rear of the lens.
I am now looking at the aperture ring which clicks and turns correctly from F2.8 to F32 and seems to turn the actuator arm but when I press the little roller wheel/actuator arm to test the stop down function, nothing happens.

I have compared this with my SP90mm macro and when I push the little wheel at say F16, the SP90mm stops down fine.

Any help would be much appreciated as the lens is in fantastic condition and I would love to be able to use it.

 

[John Koehrer]

Carbon on the valves!
Sorry, got carried away. That's what you get when you drive your Ferrari at 55mph.
You're experiencing oil on the blades. It happens as the grease used for lubricating the helical separates & the lighter component wanders into the works. It's in the blade housing and on the blades. The best way to get it out is complete dis assembly and cleaning.
On many lenses & shutters it's possible to flush clean them with naptha or lighter fluid.

 

[Zuikopath]

Hehe - I thrash it regularly to burn out the carbon so I know that's not the problem...

Oh dear - is the aperture mechanism a complete disassembly job...?

Anyone got a service manual for the SP 35-80mm...?

:confused:

 

[John Koehrer]

Zooms are a PITA. Access to the diaphragm housing is what you need & there are probably at least two barrels with cams & nylon bearings to deal with.
If you can remove the elements you may be able to flush clean the blades & housing with Naptha or lighter fluid.
Some lenses have an exposed aperture linkage just inside the mount that will stick this way but can be cleaned with a cotton bud & Naptha.