Another thing you have to check is the linear resistor - ie the sensor that detects the focal length. If the ribbon is loose from its connector, it may not giving this information. So it is stuck at a specific focal length. You can check if this is it, if the you can see picture on the LCD before you rotate the lens to the normal shooting position. I mean, when the lens is in its OFF position.
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In order to access the aformentioned connector you need to:
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1) Remove the back cover
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2) carefully remove the ribbon that is attached to the outer contacts by ***lifting up the lock mechanism*** on the back side of the connector (***the opposite side*** of where the ribbon is inserted).
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3) There are 2 connectors remaining, the smaller one is the one to check.
Another thing you have to check is the linear resistor - ie the sensor that detects the focal length. If the ribbon is loose from its connector, it may not giving this information. So it is stuck at a specific focal length. You can check if this is it, if the you can see picture on the LCD before you rotate the lens to the normal shooting position. I mean, when the lens is in its OFF position.