I too was a victim of the poor design of the shutter button and could no longer do the half press prefocus. I set out to remove the offending parts and replace them but found out after disecting the assembly that the Sony design is horribly weak and poorly designed from a mechanical point of view. I have re-engineered the shutter button and manufactured my own which will never break - sending the button and spring flying (didn't happen to me but did happen to many others). My main point here though was to correct the sharp pointed shutter actuator shaft which over 6-12 months of use leaves a dimple in the micro switch rendering the half press useless.

My solution uses a large chrome tack, an extremely small machine screw and 2 nuts, as well as the original spring and base of the button assembly. I cut off the shaft of the tack. Then I drilled a tiny hole in the center of the tack just barely large enough to force the screw through. I also countersunk the top of the tack so that the head of the screw fits flush with the top of the tack. I then punched a depression into the head of the screw with a sharp point to lock the screw to the tack. I then assembled the tack and spring with the shutter button base and screwed 2 nuts onto the screw. The top nut restricts how far up the tack moves and the second nut is right at the end of the screw. It is this nut that makes a larger plunger to correctly actuate the half press switch.


http://lh5.ggpht.com/bobnclary/SCOp-WdYSZI/AAAAAAAAAo0/n3nlEF7N_lI/s144/DSC06967.JPG This side view shows the thickness of the tack and spring underneath.



http://lh4.ggpht.com/bobnclary/SCOqCGdYSaI/AAAAAAAAAo8/W8oLjczZo9s/s144/DSC06969.JPG This image shows the screw head in the center of the tack.



http://lh4.ggpht.com/bobnclary/SCOqIGdYSbI/AAAAAAAAApE/4etTPH5l_T8/s144/DSC06971.JPG This underside view shows the 2 nuts on the screw.



The fullsize images can found at the following address:

http://picasaweb.google.com/bobnclary/CameraShutterButton


I hope someone finds this information useful. If anyone wants more information on how I did this, don't hesitate to ask.

-Bob