There is no voltage output for the notebook computer

The laptop's power adapter does not have an output voltage, which can be initially judged to be a problem with the adapter circuit of the power supply.

The enclosure is opened to reveal that the safety pipe in the adapter has been burnt black, indicating a short-circuit in the power supply circuit. Using Multimeter to Measure field effect switch tube drain electrode to ground resistance, resistance is close to 0, the field effect switch Q2 removed to measure, found that the leakage source has burned short circuit. In the overhaul of the switching power supply circuit, check out the switch tube has been damaged, and then check other components found to be normal. Then replace the switch circuit and the safety tube, the power supply after the normal start, the failure disappeared.