New welding PCB board debugging methods and skills to share

                    New welding PCB board debugging methods and skills to share

 

      For the new PCB board that you just brought back, we firstly need to check whether there are any problems on the board. For example, whether there are obvious cracks, short-circuit, open-circuit and other phenomena.

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     If necessary, check the resistance between the power supply and the ground wire if is large enough. Then install the components.Independent modules, if you're not sure they work properly, it's best not to install all the components at a time, but part of them (for smaller circuits, you can install them all at a time). In this way, it is easy to determine the scope of the fault, and when it comes to the problem,we can know where to start.

 

     In general, you can install the power supply first, and then power up to check if the output voltage is normal.If you are not sure, when the power is on (even if you are very sure, it is recommended that you add a fuse, just in case), you can consider the use of a adjustable voltage regulator with a current-limiting function.Firstly,the overcurrent protection current is preset , then the voltage value of the stabilized piezoelectric power supply is slowly increased up , and the input current , the input voltage and the output voltage are monitored . If there is no overcurrent protection and the output voltage is normal in the process of up-tuning, then the power supply part of OK.

 

    Instead, to disconnect the power, find fault points, and repeat the above steps until the power supply is normal.

 

    The other modules are then gradually installed , one module is installed , the power - up test is performed , and the power - up test is performed in accordance with the above steps to avoid burnout of the components due to a design error or an installation error.

 

    In general, there are several ways to find fault:

    1. Voltage measurement method. Firstly, we need to confirm whether the voltage of every chip's power supply is normal. Secondly, check whether all kinds of reference voltages are normal, and the working voltage of each point is normal or not.

    2. Signal injection method. Add the signal source to the input, then measure the waveform of each point in turn to see if it is normal to find the fault point. Sometimes we also use a simpler method, such as holding a tweezer in our hand. To touch the input at all levels to see if the output is responsive, this is often used in audio, video, and other amplifier circuits (but note that the hot bottom circuit or high voltage circuit, do not use this method. Otherwise, it may lead to shock.) If there is no reaction at the front level and there is a response at the later level, the problem is at the previous level and should be checked.

    3. Of course, there are many other ways to find fault points, for example, through looking, listening, smelling, touching and so on.

     "Looking" is to see whether there are obvious mechanical damage of components, such as rupture, blackening, deformation and so on.

     "listening" means listening to the sound of work, such as the place that should not be ringing, the place where the sound should ring or the sound is abnormal, etc.

     "smelling" is to check for odors, such as the smell of charred coke, the smell of capacitor electrolyte, and so on, for an experienced electronic repairman, these odors are very sensitive.

    "Touching" is to test by hand whether the temperature of the device is normal, for example, is too hot, or too cold. Some power devices, when working, will heat up, if the feeling is cool, it can basically be judged that it does not work. But if the place that shouldn't be hot is hot or the place that should be hot is too hot,it's not normal.