Diode and mosfet onboard testing

Hi, I have a fault on a laptop motherboard: After I plug in the connector the power supply protection stop the power. I think the cause it's a bad connector but I desolder it and power the motherboard with two cable directly but the problem remains the same. I test the ohm value on power connector and the tester return me approx. 450 ohm. No component with visible fault (I control with a microscope), no component with heat surface. Someone told me to control diodes,. resistors, electrolitics, and mosfet but how I can test a diode without desolder it and an 8 pin mosfet ? Someone can help me ? thanks