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Someone might say, just change to a new one and check it out. If the PCBA is good, it is a problem with the main control IC. But this is the dumbest and the last method.
First of all, some of the main control IC may be the kind of small single chip microcomputer chip, which is easy to solder and cheaper. However, some chips are in the form of BGA patches, and the solder joints are more expensive. This kind of processing is more troublesome.
Therefore, as an electronic engineer, when investigating the main control IC problem, he must first check all other related circuits, and then consider the problem of the IC itself.
Take the "no boot" phenomenon as an example to explain and analyze:
1. If the machine does not turn on, the most likely reason is that the main control IC is not working properly. Then the factor that directly affects whether the IC can work normally is power supply. First of all, it is necessary to measure whether the power supply voltage is normal, usually 3.3V or 1.2V.
If the voltage is abnormal, confirm whether there is an open circuit in the line, and check the power supply voltage circuit if there is no open circuit.
If the voltage is normal, continue to the next step.
2. Determine whether the crystal oscillator of the IC is oscillating and whether the waveform is normal. If it is abnormal, the crystal oscillator may be damaged, you can try to replace it with a new crystal oscillator and confirm.
It should be noted that the general crystal oscillator circuit is a crystal oscillator plus two capacitors for fine-tuning the frequency and waveform, but some crystal oscillator circuits also have a resistor in parallel and series.
3. In addition, you can check whether the input and output signals of the main control IC are normal. Take the remote control signal as an example, every time you press the remote control button, it is confirmed whether the output signal of the receiving head changes normally. If it is normal, the IC cannot recognize the signal. In addition, it can measure whether a certain output signal is normal, the signal is abnormal, and the part of the circuit that is controlled should not work normally.
If the signal is abnormal, it can basically be determined that there is a problem with the main control IC.
4. The last step needs to confirm whether the main control IC has poor soldering. If the solder is connected, it can be checked by X-ray machine. The cold soldering can be re-balled and soldered by the IC. If it is still the same, it means that there is no cold soldering. .
Of course, at the last step, most people will choose to directly change to a new IC to confirm.
In addition, there is a very small probability of occurrence, and it is useless to change how many ICs, because the IC is no problem. This is caused by the accuracy of the PCB design and manufacturing process. The reason is that the PCB via hole under the IC leaks copper. Once the IC is soldered on, there will be a short circuit on the Pin connection. But the chance of this happening is really very, very small.
