I have measured, and if the ossciloscoop works as a extra ground, the motherboard know stays on.
But the 3,3 is bad. If it reached 3,3V it falls again to 2,5V and 0,5 sec later again and again...
It is a regulating or power component problem, but without schema it is hard and for example I check a component with caption A016, but never find this component what it is. It's a mosfet or normal transistor or something, but its important to know witch to determine if that component is broken or not, whithout soldering.
If someone has a scherma I would be pleased...