I have a dell dimension pc - today it wouldn't turn on - does anyone know if there is a way to test the power supply before I spend money on a new one - PS-5021-7D - there are two plugs going to the mother board - i think one of them is the main supply for the board and the other i think is the low voltage control power that goes to the on/off switch - there is no voltage on this - or any of the output plugs - but without the circuit diagram I don't know if there should be without them being plugged in - don't really know about hardware so please help - might save me a few quid.