Testing Laptop Components

I have a Compaq presario 1200XL that is dead. The laptop will not power on. The power cord is ok with green indicator light on adapter on. While it is plugged into the laptop the green led indicator for plugged in power is constantly on. I want to know how to test the system board, power supply and voltage controller board to confirm working and failed components. Please don’t send me to compaq’s help sites I have already been to most of them. I need specific help on testing the circuit boards.I dont have any problem inside the box I am a tech just no laptop experience other than field replacable parts.