need help: 300 2.8 AI apertures stuck

[Bjørn Rørslett]

Is the spring keeping the aperture open still present? Set the lens to f/22. The blades ought to close. When you push the stop-down lever sideways, the aperture should open. Let the lever go and the aperture should snap back to the stopped-down position.

[brent_e]

Is the spring keeping the aperture open still present? Set the lens to f/22. The blades ought to close. When you push the stop-down lever sideways, the aperture should open. Let the lever go and the aperture should snap back to the stopped-down position.

Hi Bjørn,
thanks for the response.
It is doing that.  I can adjust the spring to be tighter, though.  I made 1 adjustment already as it wasn't returning and was weak. 


Brent

[Erik Lund]

Post some pictures of the mount and lever etc.

[brent_e]

thanks for the suggestion, Erik,

in taking some measurements and doing some more research I found out what should have been obvious to me initially.  See attached.
The aperture blade has been repaired.  It must be been broken when the lens was damaged.  I found some spare parts from a place in Finland, of all places.  Has anyone dealt with "kameratoridotfi" on fleabay???  Not only does he have a  spare aperture blade, he also has a spare tube.

I measure the amount of blade sticking out on another lens.  3mm, approximately.  The 300 blade sticks out 0.96mm or so.  Clearly that is the problem.

take a look at the photos! 

Thanks! 

[Erik Lund]

OMG that looks rough that mount, misused,,, every time you mount and dismount this lens you will be scraping and grinding your camera mount,,, It hurts my heart to look at it.

Looks like the two parts of the aperture leaver is not aligned, my guess is they should be straight.

Aperture ring should be cleaned up and checked and burrs filed down, taps straightened,,,

[Erik Lund]

On second look the whole aperture lever looks strange unoriginal, why is it in two parts,,, one screw is too long the other is too short, screws holding the lever looks like they have glue on them,,,

[brent_e]

On second look the whole aperture lever looks strange unoriginal, why is it in two parts,,, one screw is too long the other is too short, screws holding the lever looks like they have glue on them,,,

Hi Erik,
thanks for the observations.
ya, the lever was broken and repaired so it's not original.  I'm going to purchase another level and probably rebuild this lens.  It could use it.

that mount is actually off another lens.  the one that came with the 300 was bent!  I'm not sure where to source one but I can see if I can find a replacement. 

thanks!

Brent

[Bjørn Rørslett]

Brent, I have a stack of spare mounts (from 24-70 G). You might need to trim down guide flanges on its inner side to make it fit your 300, though, but that's trivial if you have a Dremel and cutting tool. Perhaps the mount points for the stray light baffle need to be re-drilled as well, but again trivial. These mounts are otherwise pristine, no burrs or dings,  and the added benefit of being ready to accept a CPU ...

Shoot me a PM if interested.

[Erik Lund]

Sometimes this site feels like a quiz show 

[brent_e]

Haha! 

Pretty helpful quiz show!

I will send you a PM, Bjørn.

Lots of fun, guys!  Thanks again. I'm grateful for this resource!

[John G]

Hi Brent
             I can,t offer any advice on your repair needs, but can suggest a USB powered Soldering Iron to help release the very small cross head screws on the rear assembly. It is very annoying when one or more get a deformed head due to a screw driver slip 
My offerings are encouragement, this is a good lens and one I will have for many years to come. It works great with a Modified TC16A to give a limited AF, but once on a moving subject will track with it in a useful way, there will be sharp images in the sequence.
I intend on adding a CPU chip to this lens myself.
Another little tip to look after the front element, I got a "Car Plan"  circular  micro fibre cleaning pad from Amazon, it is the perfect size to sit inside the lens housing. It has a small pouch on one face so your fingers can remove it and place it with ease.
I have some images on NG taken with this lens and TC.       

[brent_e]

Hi Brent
             I can,t offer any advice on your repair needs, but can suggest a USB powered Soldering Iron to help release the very small cross head screws on the rear assembly. It is very annoying when one or more get a deformed head due to a screw driver slip 
My offerings are encouragement, this is a good lens and one I will have for many years to come. It works great with a Modified TC16A to give a limited AF, but once on a moving subject will track with it in a useful way, there will be sharp images in the sequence.
I intend on adding a CPU chip to this lens myself.
Another little tip to look after the front element, I got a "Car Plan"  circular  micro fibre cleaning pad from Amazon, it is the perfect size to sit inside the lens housing. It has a small pouch on one face so your fingers can remove it and place it with ease.
I have some images on NG taken with this lens and TC.     

Thanks, John,
good tips! 

I have a TC16A waiting in the wings.  just need to get the guy to ship it!  I need to modify it, of course.


Brent

[John G]

Hi Brent
              The modification is quite straight forward, but is best done with a good quality variable temperature soldering iron. A friend of mine done this with little concerns, as I assured him, no matter what happens to the PCB on the inside, the TC, the unit will still be a MF TC if any thing went wrong, I believe this is covered on  www.Foolography,com as there is also reference to a alternative PCB.
The useful tip I can offer is to make sure the Link wire for the repositioned pin is as fine as possible, my friend chose a wire from a Headphone cable in the end,
it is as fine as hair and allows a uncomplicated reassembly of the TC. 
On the Lens mount side of the TC there is a small tab that projects and rotate when looking at it face on, from 11.O Clock to 2. O Clock. I do not follow any of the suggestions to get the TC and Camera Body to interface correctly.
I just mount TC and lens on camera, and using a small probe, a toothpick will do, rotate the tab until the EE flash disappears from the camera bodies LCD.
The tab is quite stiff when coupled to a lens so it will hold this position securely.
I have used the TC successfully on a 85mm, 135mm 200mm, 300mm 500mm.   

[brent_e]

excellent info, John!
didn't think of the wire gauge thing.  Thankfully we have some good equipment at work which should make the soldering simpler!

again, great info.  thanks!

Brent

[richardHaw]

haven't followed the thread but it does look like hack. I wonder what happened

very hard to judge but I trust that it is simple enough. I salvage my mounts from junk M rings for 3 holed one but this one has screw holes? I have 2 here but that's part of my reserve.