when desoldering chips first remove batteries from board. snip legs of chip with small diag. cutters. using a 25 watt iron with point tip and desoldering braid wick availible from radio shack.
desolder holes and remove excess chip pins with tweezers completely remove solder from holes. caution do not disturb track thru plating that goes thru holes. if possible use chip socket instead of soldering chip onto board.install chip with dot going in correct direction. replace batteries, install board. restore settings.