Minolta SRT 200 - 3rd Party Lens

I have a Minolta SRT 200 camera circa late 1970's which came with a Rokkor 45mm MD lens. I also found amongst my old items a Sakar 135 mm lens marked MC. Although the 135 lens will mount the camera, the arpeture ring does not engage -- that is, when the ring is turned the setting does not change nor does the meter coupling needle move (off camera the arp ring functions normally). All tabs seem to be in place. Can anyone help me with this compatability issue?

When the aperture ring is set at something other than wide open, see that the aperture blades do move, and can move from wide open to thier setting when the stop down tab is rotated.

Sometimes old blades can be oiled stuck in place. Too much oil from some past adjustment migrates from the pivot pin onto the leaves.

After all of my rebuilds a small whif of graphite is all they get. I have sworn off lubriating oil around apertures.