How to Check the Fault of the Light -emitting Diode Lamp Bead

What is the reason why the lamp beads are not lit up on the circuit board? How to check? First, check whether the circuit is used normally, and then make a specific analysis based on the specific circuit. However, most of the reasons are that LEDs accidentally received the right and negative polarity of LED during the installation or welding process before the installation. The actual welding is not strong), virtual welding is the main reason for the failure, especially for novices who lack welding experience. This problem is most likely. It may also be that the electricity iron leakage causes the LED breakthrough short circuit. There is part of the part of the driving circuit to connect or weld well, and some circuits may also be that the adjustment component value is not adjusted well. Before the circuit is installed, check the check and check it carefully before the power. If the light is not turned on, the power should be turned off immediately, and then the inspection should be performed. You cannot knock on the circuit board to try to find the fault. in this way. If it is a circuit with a filter capacitor, first of all, you should also use a screwdriver or wire to discharge the two feet of the filter capacitor before checking it. This step is very important! Because the filter capacitor has a high voltage of more than 1.4 times the power supply voltage (more than 1.4 times the power supply voltage ( For example, when 220V power supply can be as high as 310V), so as not to damage the human body or destroy the LED when the capacitance is survived on the capacitor or the moment the circuit is connected! Tag, check whether each LED polarity is wrong, and then use two batteries to connect the positive and negative bipolar power supplies to touch the two feet of each LED. Pay attention to the polarity of the battery power as the polarity of the LED, so as to use the polarity of the LED, so that Check whether each LED can be on. Inspection of the driving circuit, you should carefully check whether the circuit is wrong according to the circuit diagram. Pay special attention to check the rectifier bridge (the long foot is the positive electrode output, the diagonal is the negative electrode output, the other two feet are AC input) or the rectifier diode, and the voltage voltage diode pipe Whether the polarity is correct (one end with a black or white line is negative), and check whether the three electrodes of the crystal triode or the voltage integrated circuit are wrong. Alright, the explanation of the glow diode is here,