Perhaps: The below is valid for A2000 model A (rev < 4.1) and A500 rev 3 and rev 5 if the original instructions doesn't do it.
There should be no jumper between pin 1 and 31. Bend up pin 31 so that it doesn't have any contact with the socket.
Jumper pin 1 to socket 31. Make sure there's no connection to pin 31.
Solder a wire from pin 31 to 21. (from
http://www.l8r.net/)