one
Charging circuit these repairs, it is recommended to professionals to carry out maintenance.
two
Non-professional personnel can not be repaired, if not, it will damage the equipment and may also produce an explosion. If you must repair yourself: check the lithium protection chip U4 U5 U6 first. When connecting the lithium battery, use a multimeter to check that the resistance between pins U4 1, 2, and 3 is 0. Disconnect the lithium battery. If the connection between pins 1, 2, and 3 is abnormal, the protection chip works properly.
three
Then check the main control chip U1. The resistance between U1 pin 1 and the ground is 6 ohms, and the main control chip is suspected to be bad. Remove U1 and find that there is still 6 ohms between the output and the ground.
four
Then remove the capacitors from U1 one by one. When the capacitor was removed, it was found that the output was finally disconnected from the ground. The capacitor is broken down, causing the main control chip to not work.