Zenza Bronica ETRSI - Zenzanon 75mm f2.8 - aperture stopped at f2.8

Hello

i have tried to use the Zenza Bronica ETRSI - Zenzanon 75mm f2.8.

The machine currently has the bronica_etr_si_motor_winder-ei mounted and there is no battery in the body of the machine or in the winder.

The aperture preview works fine but I simply can't rotate them to replace them.

What i can do to understand where is the issue ?

can i try to put the battery in the winder and use it to see if change anything ?

can i try to remove the lens and try to change the diaphragm when the lens is not mounted ?

Do you mean you can't turn the aperture ring on the lens? Sounds like it might be stuck. Try a little harder to turn it but don't force it, it may need repairing.