replace your ccd

Is the hum coming from the front of the camera, where the lens is? If such is the case and you don't see any image on the viewfinder, it seems as if the "iris" is not opening. Take the camera into a fairly dark room and look in from the lens. You should see the "iris" nearly fully open. Now shine a flashlight into the lens and you should see the "iris" close. You should also hear the iris motor. It functions much like the iris in your eye.