In this case, the instrument can no longer help. You can try to judge the possible range of the problem according to the current and voltage, and try to reduce the range as much as possible. Some experienced engineers may be able to quickly determine the problem area, but they cannot be 100% sure which specific components are broken. The only way is to try to replace the suspicious component until the problem component is found. Last year, my laptop motherboard had water damage. When the computer was repaired by the repairman, it also encountered that it could not detect the problem. During the repair process, I replaced three components, namely the power supply chip, diode, and USB charging component (It is the blue socket of the notebook, which can charge the device when it is turned off). Finally, it is also through a wave of detection and investigation to replace the suspicious chip, and it is finally detected that a component on the side of the South Bridge chip is short-circuited.

The above is actually the problem of electronic components. Of course, since the PCB circuit board is the foothold of the components, then the circuit board problem must also exist. The simplest example is the dead tin part. Due to the manufacturing process, In the process of PCB corrosion, disconnection may occur. In this case, if you can’t make up the wire, you can only use a thin copper wire flying wire to solve it.

When the PCB circuit board problem is not obviously damaged, it is indeed very troublesome to find out. In the process of troubleshooting, you need to concentrate on it. After the problem is found, there will be an inexplicable sense of accomplishment. In this mood, I often like to investigate some difficult-to-maintain boards. That is a kind of fun.