LED Flashlight Maintenance

1 death LED does not light, replace the LED can be had, however, to note that ± polarity cannot be reversed.
2 lead-acid battery is damaged, resulting in the charge and discharge, plug can be used.
3 high voltage buck capacitor damaged or rectifier diode overvoltage damage, resulting in the charge, this time with ordinary analog universal meter can detect and solve the problem.
4 pull switch connection is bad or damaged cannot pass.