AI Tab not springing back on FE or EM

[nicholas marrone]

Hello,

 

I am having a problem now with two different cameras and was

wondering if anybody could shed some light on the situation. The

problem existed with the EM intermittently and now completely and my

FE developed the same problem last weekend very suddenly. I am not

sure what happened.

 

The problem is that when an AI lens pushes the AI tab over from the

widest aperature and then goes back to wide open, the AI tab does

not spring, snap back into place. I tried to take off the mounting

ring to see whether dirt or sand had gotten inside somehow and, with

the ring off, the mechanism works fine. With the ring on loosely it

still works. With the ring on snugly it stops. With the ring on

loosely and the weight of a lens on it it stops.

 

Any help is appreciated.

[alan_merrigan1]

Perhaps it became bent. Lay it on a flat surface such as a mirror and check. Also, check to see if it does this with another lens. Perhaps the lens mount is interfering with the AI ring.

 

Good luck.

[scott_warn]

The first question is, are you a smoker? Smoke residue can build up and cause these rings to gum up. Also exposure to cooking fumes will cause this. A simple CLA will solve the problem.

 

As a temporary fix the solution is as close as the local hobby shop. Get some 0.005 inch brass shim stock and make up some shims for the lens mount. Shim the mount equally at each mounting post and the additional clearance will free up the action. You may be concerned about throwing the focus out of adjustment, this won't happen because you haven't changed the mirror to view screen alignment and focusing is only the action of moving the lens closer or farther away from the film plane. This shimming could throw the infinity focus out, but 0.005 inch is a small distance and most lenses do have a bit of extra slack at the infinity stop. The lenses that do not have that extra slack may require stopping down 1 or 2 stops at infinity so that the depth of field covers up the focus error.

[nicholas marrone]

Thanks for the assistance. No, I am not a smoker, but the problem started after I went to the beach one day. I changed the lens once but was very careful about letting sand get in. Maybe I wasn't careful enough. It looks like it needs a cleaning and adjustment.