How to use 220V light bulb to quickly eliminate the switch power failure

Switching power supply circuits are easy or difficult, with different powers and output voltages. When repairing, you need to grasp the core essentials, be fully familiar with the basic structure and characteristics of the switching power supply, and be familiar with the basic conditions for their operation. With more hands-on experience, you can quickly eliminate the fault of the switching power supply . The following introduces a technique for repairing the switching power supply using a 220V light bulb.

When repairing various switching power supplies, use AC 220V200W to connect in series between the hot end main filter capacitor and the switch transformer, and disconnect the load at the cold end to prevent the switch tube from burning again. According to the brightness of the bulb, you can judge whether the current of the switch tube is overcurrent. For example, it is very bright when it is turned on, indicating that there is an overcurrent phenomenon in the switch tube. There are many reasons for this: such as soft wear of the switch tube, out-of-control circuit of the voltage stabilization link, spike absorption circuit, short circuit of the switch transformer, short circuit of the secondary end, normal startup bulb is slightly bright or not bright and the voltage of each group at the secondary end is normal. If it is not bright at all and there is no voltage output, the cause may be the open circuit of the switch tube, the starting circuit, the voltage stabilization link circuit, etc. When this fault occurs, short-circuit the 1.2 pins of the optical coupler to determine the approximate location of the problem. If the bulb is bright at this time, the fault is in the cold end voltage stabilization link. If it is not bright, check the starting circuit, voltage stabilization link circuit, and feedback circuit of the hot end.

In addition, when repairing the line circuit, use a 200W bulb string +B to the high-voltage package, and you will have a clear ability to judge the short circuit between the high-voltage package turns and the line load overload. If it is very bright when turned on, it means that there is a problem with the line circuit, and check whether the line load is short-circuited. At this time, short-circuit the base B and emitter E of the line tube to see if the bulb goes out. If it goes out, it means that the AC is short-circuited and the high-voltage package has a problem. Another tip: when the machine is turned on normally, the bulb will slowly light up as the image tube lights up, and the brightness of the 200W bulb is 25W, and it changes with the brightness of the image tube.

This method uses a step-down repair method, using the characteristics of the light bulb to monitor the load current to determine the approximate location of the fault point, which can effectively prevent further damage to the switch tube or line tube.