Originally posted by donpjt The A pin can be swung back and forth in A setting. Only in the fully open setting it remains fixed. ie, at F 4.7 I'm assuming the A pin is the one next to the inner barrel
The "A" p[n or contact is the only pin or contact on the lens mount that should change when you move the aperture ring to or from "A". On the "A" setting it should extend out from the flange about 0.5-1mm. With the aperture ring set at anything else the contact should be flush or slightly below the flange. The contact is spring loaded and will depress when pressure is applied to them. This is to allow you to mount or dismount the lens. The "A" series lens use a system of non-conductive plugs and the bare metal of the mounting flange. In this case the "A" contact will be the only contact with a rounded pin.
The position of the pins/contacts is illustrated on this webpage which gives some explanation on the function of the contacts:
http://www.robertstech.com/matrix.htm
If you have a multimeter or circuit continuity checker you can test to see if the pin is conducting properly.