Hasselblad V lens: Sporadically can't adjust aperture until shutter is cocked.

[theHUN]

Hi all,

I hope this is the right sub-forum for my question.

I have a Hasselblad 250 mm SA CF lens on a non-native body. In order to keep the internal shutter open at all times, I leave the lens in F-mode. About once a month (but I use the lens sporadically) I run into an issue where I am using the lens at f/8 and I hear a click from the lens only to see that the aperture is now at f/5.6. Adjusting the aperture ring, shifting the DOF knob on/off, or gently tapping the lens do nothing, the lens stays fully open no matter what. But when I switch out of F-mode, the internal shutter close, and after cocking it again I finally regain control of the aperture diaphragm. Does anybody know why this is happening? I would like to prevent this from happening as it requires me to unmount the lens from the body and this can introduce dust on the sensor when I am out in the field.

Thanks.

[theHUN]

A repair place suggested that i contact Hasselblad directly, and Hasselblad informed me that they do not service this lens anymore. Bu they did suggest that I toggle the DOF switch a few times next time is happens, so I will give that a try. And if it doesn't work, unmounting the lens is always an option, although a slight nuisance.