Vivitar 2x Macro-Focusing Teleconverter

[nikolympus]

I just acquired one of these in Nikon mount. The teleconverter says N/AI, and its obviously designed for auto-indexing.

Problem. When I attach a lens to it, like a 50mm f/2 nikkor, the lens only operates on maximum aperture. Its stuck on f/2.

I took both ends of the teleconverter apart to see what was stuck. There is only one way it goes back together, and that is with the auto-indexing tab on the lens end of the converter in a little notch that holds it in place. There is actually an indentation that the other end of AI tab has to be into during assembly.

Is it possible that Vivitar designed the Nikon-mount AI teleconverter to use only the maximum lens opening? It doesn't seem likely, but it looks like it.

If any one can give advice, thank you.

[D1N0]

Highly unlikely since it is meant to turn a 50mm lens into a 1:1 macro. I have the PK version and that stops down no problem.

[stevemark]

[nikolympus]

Thank you for the opinions. I agree that it would not be built the way it seems to work.
This converter seems to be in good shape, except the AI ridge (the part the sticks out by the mount and catches the AI tab) does not move independently of the lens mount, as it normally does on a lens. Therefore the F-stop on an attached lens cannot be changed whether it is on a camera or not. I was looking at the internal linkages between the lens-end AI tab and the camera-end tab. I'll look elsewhere.

[nikolympus]

I found the problem. (Apparently the forum won't let me post a picture yet.)

On a typical Nikkor the AI ridge (proper name?) is one piece with the f-stop ring. On this converter, having no f-stop ring, it is a separate ring that sits outside the mount flange and inside the grip ring you grasp to mount the teleconverter.

)flange)ai ring)outer grip

The ring with the AI ridge is so tight in its channel that it will hardly move.
Any suggestions on how to free it up? It doesn't seem to have anything sticky in the channel, or to have been distorted. There is lube on it when I pull it out.

Thank you.

[cooltouch]

I have a few of these teleconverters in various mounts, including Ninon AI. One of my AI TCs exhibited this same problem. The ring that holds the tab would stick in its channel. I fixed this issue, but it was several years ago and I don't recall now what I did. But I do have a few suggestions. 1) lubricate the ring and its channel with some light machine oil, like sewing machine oil, then just move the tab all the way in both directions a few hundred times. This may have the effect of sort of "honing" the ring to its channel so that it will more freely move. 2) Disassemble the TC and, using some fine sandpaper, sand down the sides of this ring so that there will be more clearance between it and its channel. Alternatively, you could use some rubbing or polishing compound, place it on the ring and channel and move the ring back in forth a bunch of times. This compound will have the effect of honing the ring to the channel. 3) Inspect the ring for any bends or bumps. If it is not a smooth arc, it may be binding in spots because of these bends or bumps. If it has any, see if it is possible to straighten them. Using a light hammer on the ring, supported by a caul, may get the job done. I don't recommend trying to re-bend it. You'll likely just end up with a distorted ring as a result.

[nikolympus]

Thanks very much. I did get it working using a similar approach to your recommendation.
I used fine sandpaper (240, 600, 1200) and slowly removed plastic from the ring until it moved smoothly. I decided to leave it dry instead of oiling it.
I'm guessing it was various plastics aging differently. Or, it was a reaction between the lube in the channel and the plastic, again over years.
Cool lens now that it works!

Thanks again for the help.