Minolta 75-150 aperture ring not working

sybersitizen wrote:

FrancoD wrote:

OK. The aperture blades are meant to be closed when the lens is off camera

That's incorrect. I have three Minolta MD lenses here (the type the OP has), and their diaphragms open and close as the ring is rotated when the lenses are not mounted.

and then should be fully open when mounted on the camera to then close down to the selected aperture when you take the photo.

That part's correct.

To the OP: There must be an internal problem with the linkage. The video below is not for your specific lens, but the structure might be similar. You'd have to at least remove the rear of the lens to see what's going on.

I've removed the rear of the lens and have managed to put it back together. The aperture ring came off and I was lucky that the ball bearing was ejected inside the lens body (so I could retrieve it).

Linkage issue undetermined:

I will have to look at it again (should have taken a picture), but there is a little metal piece screwed onto the aperture ring, which is what I believe should link the aperture ring to the aperture pin. It might have been somehow put in incorrectly and isn't interfacing correctly. I will have to post a pic, but it is impossible to see how it interfaces when the aperture pin mechanism is put on the back of the lens.

Miscellaneous Reference:

The YT video below show that the aperture control pin is slow to snap back, although that is not the major problem. There are springs to the left of the aperture of the aperture pin, which are visible as I push it to open the aperture, but I don't believe they're what should be pushing it back (as they're on the wrong side of the pin to do that). On the side of the aperture ring facing the lens internals, there is a wire wound around a screw which moves as the aperture pin is pushed — if that is responsible for the pin snapping back into place, perhaps I need to increase the wire tension somehow? The actual aperture is very smooth and instantly snaps back into place when I control it directly using a screwdriver inserted down to the inner aperture pin.

https://youtu.be/6bY2Y3Qhhio

Below is a picture of the aperture ring that I accidentally took off as well. I was lucky that when the ball bearing sprang out, it went inside the lens internals and I could simply dump it out (otherwise I'd have a de-clicked lens). It was also tricky seeing where to put the ball bearing.