Minolta 75-150 aperture ring not working

Started 3 months ago | Discussions
David Heinrich
David Heinrich Regular Member • Posts: 210
Minolta 75-150 aperture ring not working

I managed to score a clean condition Minolta 75-150 from eBay for $20, but the aperture ring doesn't work and the aperture is stuck at f/22 (it was listed as "not working" and the picture showed the stopped down aperture, so I figured that was the case).

I can open the aperture wide open using the lever on the back of the lens, so there is not a problem with the aperture blades being sticky. It seems that the aperture ring is disconnected from control of the aperture (I do hear the clicks).

Any thoughts on repairing this and what might be the issue?

neilt3
neilt3 Senior Member • Posts: 2,291
Re: Minolta 75-150 aperture ring not working

If the lens is marked "MD" then there is a kick on the aperture ring to lock it at f/22.

This is so that when the cameras that have shutter priority or Program mode are in use , the camera can select the appropriate aperture for correct exposure .

I'm not at home at the moment , but can post a picture later to show the lug I mean ?

Does your lens have this feature ?

Although it does sound as if you can turn the aperture ring ?

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David Heinrich
OP David Heinrich Regular Member • Posts: 210
Re: Minolta 75-150 aperture ring not working

neilt3 wrote:

If the lens is marked "MD" then there is a kick on the aperture ring to lock it at f/22.

This is so that when the cameras that have shutter priority or Program mode are in use , the camera can select the appropriate aperture for correct exposure .

I'm not at home at the moment , but can post a picture later to show the lug I mean ?

Does your lens have this feature ?

Although it does sound as if you can turn the aperture ring ?

Thank you for replying

It is marked as an MD lens. The aperture is not locked at f/22 by the aperture lock switch. I can turn the aperture ring, it is just that that doesn't open up the aperture beyond f/22 — it is suck on f/22.

I attached pictures of the back of the lens below.

FrancoD Forum Pro • Posts: 16,280
Re: Minolta 75-150 aperture ring not working

David Heinrich wrote:

I managed to score a clean condition Minolta 75-150 from eBay for $20, but the aperture ring doesn't work and the aperture is stuck at f/22 (it was listed as "not working" and the picture showed the stopped down aperture, so I figured that was the case).

I can open the aperture wide open using the lever on the back of the lens, so there is not a problem with the aperture blades being sticky. It seems that the aperture ring is disconnected from control of the aperture (I do hear the clicks).

Any thoughts on repairing this and what might be the issue?

OK. The aperture blades are meant to be closed when the lens is off camera and then should be fully open when mounted on the camera to then close down to the selected aperture when you take the photo. .

What camera body are you using ?

sybersitizen Forum Pro • Posts: 21,723
Re: Minolta 75-150 aperture ring not working

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.

David Heinrich
OP David Heinrich Regular Member • Posts: 210
Re: 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.

My one doesn't open and close whether the lens is mounted or not, so I'll have to review the video you provided.

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.

Thank you very much for the help.

David Heinrich
OP David Heinrich Regular Member • Posts: 210
Re: 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.

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