Laptop computer can't recover from traditional power failure.

1, the fuse is blown. In general, the main reasons for fuse blowing are: abnormal components of rectifier filter and switch circuit, unstable mains supply, etc. Such as rectifier diode breakdown, filter capacitor and switch tube damage. Check whether the components on the circuit board are burnt out and whether the electrolyte overflows.

2. No DC voltage output or unstable output voltage. If the fuse is intact, first measure the grounding resistance of the system board +5V power supply with a multimeter. If it is greater than 0.8 Ω, the circuit board is not short-circuited. Then temporarily remove unnecessary hardware in the computer, such as hard disk and CD-ROM drive, leaving only the motherboard, power supply and buzzer, and then measure the terminal voltage of each output. If the output is still 0V at this time, the control circuit of the power supply is faulty and should be carefully searched.

3. The power load capacity is poor. If the power load capacity is poor, it can only supply power to the motherboard and floppy drive normally after booting. When the hard disk is connected to the CD-ROM drive, the load capacity is insufficient, which causes the screen to turn white and cannot work normally. The possible reasons are that the zener diode, rectifier diode and filter capacitor are damaged, and the transistor working point is abnormal. If the operating points of the transistors are normal, replace each transistor in the oscillating circuit or readjust the operating points of the transistors and try again.

4. Burn the safety tube repeatedly. If the power supply fuse is blown frequently, the fault is likely to appear in the circuit before the primary winding of the transformer. At this time, the safety tube can be replaced for power-on test. If the fuse tube of commercial power is turned on immediately and burned out, it proves that the AC input circuit is short-circuited, the source fan of the rectifier bridge can rotate normally, and the DC output voltage is normal, indicating that the fault lies in the noise filter circuit.