take a look at the stickey:
okay i took off the cover over my on button for my laptop compaq v5000, it looks like there are 4 points i can solder wires to, how do i find which points to solder the wires too?
1. with the laptop off, remove power cable and battery. use a multimeter to test which points to solder.
2. with the laptop off, use a wire as a jumper to short out 2 points at a time. when the laptop turns on you'll know which points to solder.
Note - You need to physically press the button to check the contacts with a multimeter.