We know that the use of integrated block, there is always a pin and printed circuit board on the "ground" line is welding, in the circuit called the ground feet. As the integrated circuit is used within the direct coupling, therefore, the other block of the integrated block and the ground pin there is a certain between the DC resistance, this determination of the DC resistance is called the equivalent DC resistance within the foot, referred to as R inside. When we get a new integrated block, you can use a multimeter to measure the internal equivalent DC resistance of each pin to determine its good or bad, if the pin of the internal equivalent resistance R and the standard value of the match, indicating that this The manifold is good, otherwise the difference between the standard value is too large, indicating that the internal block damage.
It is important to note that since there are a large number of non-linear elements such as triodes and diodes inside the manifold, a single resistance can not be judged in the measurement. It is necessary to check the test leads again and obtain the positive and negative Two resistance values. Only when R inside and outside the resistance are in line with the standard, in order to conclude that the integrated block intact. In actual repairs, road measurements are commonly used. First measure the pin voltage, if the voltage is abnormal, can disconnect the terminal connection to determine the terminal voltage to determine whether the voltage changes are caused by external components, or within the block caused. Can also be used to measure the external circuit to the ground between the DC equivalent resistance (called R) to judge, usually measured in the circuit of a pin between the pin and the ground between the DC resistance (in the road resistance), the actual Is the R and R outside the parallel total DC equivalent resistance. In the repair often in the road voltage and road resistance in conjunction with the measurement method used. Sometimes in the road voltage and the resistance in the road deviation from the standard value, not necessarily the block damage, but the damage to the external components, so that R is not normal, resulting in road voltage and resistance in the road. At this time can only measure the internal block DC equivalent resistance, in order to determine whether the block is damaged.
According to the actual maintenance experience, in the road detection integrated circuit within the DC equivalent resistance can not be assembled from the circuit block down, just the voltage or abnormal resistance in the circuit and the circuit off the circuit, while the ground pin with the circuit Board off, the other feet to maintain the status quo, measured between the test foot and the ground pin R within the positive and negative resistance value can determine its good or bad.
In the measurement of the majority of the pin, multimeter with R × 1k block, when the individual pin R is very large, the use of R × 10k block, this is because R × 1k block the battery voltage is only 1.5V, when the integrated block When the internal transistor is connected in series, the voltage inside the meter is too low to enter the normal working state of the transistor in the integrated block. The numerical value can not be displayed or is not accurate. In short, the test should be carefully analyzed, flexible use of various methods, explore the law, so fast and accurate to find out the fault.
