Mamiya Sx lens auto diaphragm pin modification and adapting.

kiddo · Joined: 29 Jun 2018 Posts: 1121

Thanks so much for reviving this issue. I've cleaned , partially the iris, without pulling em out, as I could reach hoy get em out (yet) . I've bought this lens like new, but it arrived to me without the iris working , aperture ring was moving, but once opened ,I've seen the lever from the thin ring that sits on theount, it was out of the inner lever that mover iris . Besides , once I've put all toghter, just can't find the proper way to put back the aperture ring , my issue is with that spring that pushes the pin, do I need to press it before connecting the aperture ring? Tomorrow I'll check again that spring, as it might not look like yours , if I remember correctly. On top of the iris ,I've seen two big holes on that ring, so I assume I should make a special tool to unscrew it without damaging the blades , or maybe a deep reaching rubber tool might work. Now, I've left it half opened ,had to relax a bit before touching it again lol. Thanks again for taking time and helpinge out ., I really aprecy it. I have two sonars c/y but I was really curious about this SX , as some very experienced fellows around here ,just talked so good about it, I think is just the ⛽ GAS

55 · Expire: 2022-06-15

You're welcome, kiddo. And I understand about wanting another lens - even if I already have a good one. Wink

I hope you'll succeed cleaning the iris. Mine is slow, but I don't want to get into all that so I'm going to leave it as is.

Regarding the spring / lever you mentioned, here's a photo of the way I orient it before trying to reattach the aperture ring / mount to the lens body:

#1

It's easier for me to get the aperture ring / mount to fit on the barrel if I don't push on the external stop down pin when attempting to reattach.
The green arrow shows the direction the spring will push on the (inner barrel) stop down lever when the spring is pushed by the external stop down pin.

But if you want to permanently depress the external pin -using Kathmandu's "jacket" method, for example- it might require more fiddling to get the aperture ring / mount on properly.

I haven't needed to fix my stop down pin because I use an adapter for Canon EF which allows use of SX lenses with no modifications:
Click here to see on Ebay

kiddo · Joined: 29 Jun 2018 Posts: 1121

I've tried the jacket, and it resists to fit , it might be because there would need a very specific size of the jacket ? Like the pin on the outside of the ring should be totally on the flat surface of that same ring?

55 · Expire: 2022-06-15

Is it working now, kiddo?
In my experience with other lenses, the jacket usually needs to be just a couple mm in length to do its job. I try to get the external stop down pin flush with the mount surface or have it protruding just a small amount - less than one mm.

kiddo · Joined: 29 Jun 2018 Posts: 1121

Well, i have removed and cleaned iris ,Wich was not that hard, but there's something that's not right, here's a pic of the stop down lever Wich won't move anymore on the left, so that's the max. The thin copper ,that has a bended end inside should connect to that stop down lever, but none of them would move further to engage em together.

kiddo · Joined: 29 Jun 2018 Posts: 1121

The steps to clean iris are.
1.unscrew rear cemented group Holden by a ring
2. Unscrew front group with rubber (will come off with the hood )
3. Remove 3 screws in front group , that are holding the aperture group, they are located between this group and the exterior barrel
4. Once removed the aperture group, there are 3 very little screws on the exterior ,that are holding the inner ring that holds in place the iris blades. Be carefull ,just unscrew them a little bit ,the necessary to remove the inner ring, don't lose them ,they are very small and I've used a 0,9mm plane screwdriver as 1.2 wouldn't fit to unscrew them.
Piece of cake, I'm not sure where would the problem be with the aperture ring, but one day, It should be working. Lol

kiddo · Joined: 29 Jun 2018 Posts: 1121

kiddo · Joined: 29 Jun 2018 Posts: 1121

It might have been that ,when I've put back the aperture group, and hold in place with the 3 screws , i haven't put back properly? Could you please post a pic with the stop down lever on the extreme sides ,it might be there the issue with it? I mean the lever that comes from the aperture group and need to be connected to the thin ring

55 · Expire: 2022-06-15

Is this what you wanted, kiddo?

#1

kiddo · Joined: 29 Jun 2018 Posts: 1121

Yes ,many thanks, as I've suspected , i would need to loose the 3 screws that hold the aperture group and twist it until the thin ring's bented lever would fit inside of it. I'm not experienced in opening lenses very often ,as you can tell. Really appreciate your help.

55 · Expire: 2022-06-15

You're welcome, kiddo.

kiddo · Joined: 29 Jun 2018 Posts: 1121

I've been dealing with this lens for a while , supposed to be fix but after a while would just brake again.
There are two issues, as far as I can reach to.
First of them woulbe be the lever with spring that is actuated by the pin from the mount, is just jumping over the lever that I'm actuating with my finger in the picture., and is always happening on minimum focus distance ((when the inner barrel is far away from the mount).
The second one is that I am not sure how to limit the aperture of the blades properly , I found out that part it is the pin actuator that limits the aperture of the blades and the second one would be the two screws that keep the lever of the aperture ring (second picture), but doesn't matter what I do, it's just not properly aligned ,so what would be the proper way to do it?
I've tried this lens and is so good but it's just giving me hard time to out it together and make it work . (410 error imposible to upload pictures)