Pcb manufacturer look for faulty PCB board methods
1. Pcb manufacturer measures voltage method to find faulty PCB board
For Pcb manufacturer, the first thing to confirm is whether the voltage of each chip’s power supply pin is normal, and then check whether the various reference voltages are normal, and if the working voltage of each point is normal. For example, when a normal silicon triode is turned on, the BE junction voltage is about 0.7V, and the CE junction voltage is about 0.3V or less. If the BE junction voltage of a triode is greater than 0.7V (except for special triodes, such as Darlington), it may be that the BE junction is open circuit.
2. To find faulty PCB board via signal injection method
The pcb manufacturer adds the signal source to the input, and then measure the waveform of each point in turn to see if it is normal to find the fault point. Sometimes we will use a simpler method, such as holding a tweezers by hand, touching the input terminals of each level to see if there is any reaction at the output, which is often used in audio, video and other amplifier circuits (but note that the hot backplane circuit or circuits with high voltages cannot use this method, otherwise it may cause electric shock. If there is no reaction once touching the previous level and there is a reaction when touching the next level, the problem is at the previous level and should be checked.
3.Other methods for pcb manufacturer to find faulty PCB boards
There are many other ways for pcb manufacturer to find fault points, such as watching, listening, smelling, and touching.
“Look” means to see whether the component has obvious mechanical damage, such as cracking, blackening, deformation, etc.;
“Listening” refer to listen to whether the working voice is normal. For example, some things that should not be ringing but ringing, the portion where the ringing is not ringing or the sound is not normal, etc.;
“Smell” means to check for odor, such as the smell of charred, the taste of the capacitor electrolyte, etc., odor is very sensitive to an an experienced electronic maintenance person ;
“Touch” refer to test the temperature of the device by hand, such as too hot, or too cold.
Some power devices will generate heat during working. If they are cold, pcb manufacturer can basically be judged that they are not working. But if the hot place is not hot or the hot place is too hot, it will not work. General power triodes, voltage chips, etc., working below 70 degrees is completely ok. What is the concept of 70 degrees? If you put your hand on it, pcb manufacturer can stick to it for more than three seconds, which means that the temperature is about 70 degrees (note that you should try it first, don’t burn your hands).
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