Lenovo laptop power adapter after production, electric light is not bright, the output voltage of 0 v

Lenovo laptop power adapter after production, electric light is not bright, the output voltage of 0 v - 2017 05 - 25 author: click: extract: lenovo laptop power adapter after production, electric light is not bright, the output voltage of 0 v to observe this machine after add electric light is not bright, the output voltage of 0 v. Open the shell, take out the circuit board, observation circuit boards that insurance tube burst, circuit board on the back of the whole bridge near the pins have obvious play the fire signs of corrosion, ac input to insurance tube between the copper foil was burn out, insurance tube to an input of the whole bridge foot line between the copper foil were burn out, obviously circuit happened serious high voltage short circuit. So the whole bridge and power switch tube Q1 ( FS5KM) Welding. Measured the whole bridge was not damaged, power switch tube ( FS5KM） Also is normal, measuring the resistance the R20 ~ R23 were normal, then use alcohol to clean carefully by ablation of the circuit board, in the process of cleaning circuit board found that the positive plate welding of the main filter capacitor C7 and line breaks. Then connected by wires will be burn out of the copper foil is good, change insurance tube, welding the positive plate welding of the main filter capacitor C7, and the other solder joints after repair welding, troubleshooting. The analysis more cause, the cause of the disabled is probably, in the adapter fell to the ground, the circuit board is not clean up the solder beads or element pin conductor drop, such as the high pressure components to short-circuit pins high voltage short circuit, cause burning insurance tube and circuit board copper foil. Fortunately, not cause massive damage to components. The power adapter production