Right so it may not be the power supply. I have left the computer overnight without the battery in and without the power cable in and this morning its acting up just the same. It is totally dead. imm guessing now that it must be something to do with the sister board that contains the ethernet port, usb, graphics output and the jack istelf.
This is not true in all cases but I've found it to be true most of the time >
An unloaded power supply will show the proper voltage well inside the tolerance range. It might even be higher slightly than the spec-ed voltage. Nothing to worry about.
What happens is when you loaded the power supply by connecting a device, the regulators adjust to the load. Then if you put a meter on the power to load connection you see the proper voltage.
But if the power supply is a flake you may see the voltage either way below what is required or it might just crash altogether.
Here's the poop on how it works. Amps is the amount of power. Voltage is the push behind it. If there's not enough push or none at all it just doesn't deliver the goods.