Circuit board maintenance is an emerging repair industry. The automation level of industrial equipment is increasing, so the number of industrial control boards in various industries is also increasing. After the industrial control boards are damaged, the high cost of replacing circuit boards (ranging from several thousand yuan to tens of thousands or hundreds of thousands of yuan) has become a very headache for enterprises. In fact, the vast majority of these damaged circuit boards can be repaired in China, and the cost is only 20-30% of purchasing a new board, which takes much shorter time than ordering a board abroad. Below is an introduction to the basic knowledge of circuit board maintenance. Almost all circuit board maintenance has no drawings and materials, so many people are skeptical of circuit board maintenance. Although various circuit boards are different, what remains unchanged is that each circuit board is composed of various integrated blocks, resistors, capacitors and other devices. Therefore, circuit board damage must be caused by the damage of one or some of the components. The idea of circuit board maintenance is based on the above factors. Circuit board maintenance is divided into two parts: inspection and maintenance, with inspection occupying a very important position. Test the basic knowledge of repairing each component on the circuit board until the faulty parts are found and replaced, and then a circuit board is repaired. Circuit board detection is the process of finding, determining, and correcting the faults of each electronic component on the circuit board. In fact, the entire testing process is a thinking process and a testing process that provides logical reasoning clues. Therefore, testing engineers need to gradually accumulate experience and continuously improve their level in the maintenance, testing, and repair process of circuit boards. General electronic devices are composed of thousands of components. During maintenance and repair, it would be very time-consuming and difficult to detect problems by directly testing and inspecting each component in the circuit board. So the targeted maintenance method from the phenomenon to the cause of the fault is an important maintenance method. As long as the problem is detected on the circuit board, maintenance is easy