How to detect the quality of integrated block

Nowadays, electronic products are often damaged by an integrated circuit, resulting in one or several parts not working normally and affecting the normal use of equipment. So how to test the quality of integrated circuits? Usually, there are many integrated circuits in a device. When you get a device with an integrated circuit fault, you should first judge the approximate location of the fault according to the fault phenomenon, and then gradually narrow down the possible location of the fault through measurement, and finally find the fault. In order to find the fault, it must be detected. Usually, maintenance personnel use the method of measuring pin voltage to judge, but this can only judge the approximate part of the fault, and some pins are insensitive or even unresponsive. Even in the case of voltage deviation, including the damage of peripheral components, the internal faults of the integrated block must be strictly distinguished from the peripheral faults, so it is difficult to detect the integrated circuit by a certain method alone and must rely on comprehensive detection means. Taking multimeter detection as an example, this paper introduces its specific methods. In actual repair, road measurement is usually used. First, measure the pin voltage. If the voltage is abnormal, disconnect the pin to measure the terminal voltage, so as to judge whether the voltage change is caused by peripheral components or the inside of the integrated block. It can also be judged by measuring the DC equivalent resistance between the external circuit and the ground (called R external). Usually, the DC resistance (in-circuit resistance) between the manifold pin and the grounding pin measured in the circuit is actually the total DC equivalent resistance in parallel with the outside of R. In repair, online voltage and online resistance measurement methods are often used in combination. Sometimes the loop voltage and loop resistance deviate from the standard value, not necessarily because the integrated block is damaged, but because the peripheral components are damaged, which makes the R circuit abnormal, thus causing the loop voltage and loop resistance to be abnormal. At this time, only by measuring the DC equivalent resistance inside the integrated block can we determine whether the integrated block is damaged. We know that when using the integrated block, there is always a pin soldered to the "ground" line on the printed circuit board, which is called the ground pin in the circuit. Due to the direct coupling in the integrated circuit, there is a certain DC resistance between other pins of the integrated block and the grounding pin, which is called the equivalent DC resistance inside the pin, or R for short. When we get a new integrated block, we can judge whether it is good or not by measuring the internal equivalent DC resistance of each pin with a multimeter. If the internal equivalent resistance r of each pin is consistent with the standard value, it means that the integrated block is good; Otherwise, if it is too different from the standard value, it means that the integrated block is damaged internally. One thing must be paid attention to when measuring. Because there are a large number of nonlinear components such as triodes and diodes in the integrated block, it is still impossible to judge the quality of a resistance value by separate measurement, so it is necessary to replace the probe and test it again to obtain the resistance value in both positive and negative directions. Only when the positive and negative resistance values in R meet the standard can we conclude that the integrated block is in good condition. According to the actual maintenance experience, it is not necessary to weld the integrated block out of the circuit when detecting the DC equivalent resistance inside the integrated circuit. Just disconnect the pin with abnormal voltage or in-circuit resistance from the circuit, and disconnect the grounding pin from the circuit board at the same time, and keep the other pins intact, and measure the positive and negative resistance values in R between the test pin and the grounding pin to judge whether it is good or not. For example, if the tap voltage or resistance of the integrated block TA7609P in the TV set is abnormal, you can cut off the tap and pin ⑤ (grounding pin), and then measure the resistance between the tap and pin ⑤ with the internal resistance of the multimeter. After measuring a value, replace the probe and test again. If the integrated block is normal, the DC equivalent resistance R should be 8.2kΩ when the red contact pin is grounded and 272kΩ when the black contact pin is grounded, otherwise the integrated block will be damaged. In short, it is necessary to analyze carefully, use various methods flexibly, explore the law and find out the fault quickly and accurately.