How to replace some common 3.3V/5V power IC for laptop ?

How to replace some common 3.3V/5V power IC for laptop ? Sometimes when we are repairing , we found a power IC is bad , but we have not it at that time . what should we do ?  of course we choose to replace . we list some replacing number : 
1, MAX1632   MAX1630   MAX1633   MAX1635   MAX1902    SC1403           can replace each other
2, MAX1631   MAX1634   MAX1901   MAX1904   can replace each other
3, MAX1999   MAX1997    can replace each other
4, SI786   MAX786        can replace each other
5, MAX785   MAX786    can not replace each other  please note .
Hope every friends more communication. Your loyal friend - Pinkney , http://www.htic-tool.com/  



from https://plus.google.com/u/0/b/107329939332162905445/+Htictoolchipset/posts