When dealing with hardware, it is inevitable to encounter some PCBA pins or network short circuits. The most difficult and challenging issue among them is the problem of power short circuit, especially when the board is relatively complex, there are many circuit modules, and chips such as BGA are not easy to measure, but also when there is a 3.3V short circuit.

PCBA power supply is short circuited, and it may be common for everyone to conduct level by level inspections. If no issues such as tin connection are found during visual inspection, first check if the corresponding power chip is damaged (after disconnecting the secondary circuit, it appears to be a short circuit), and then check which circuit modules in the short circuit network are using this power supply. At this time, the magnetic beads or 0 Ω connected in series on the power supply are working. Slowly eliminate and narrow the range until the short circuited device is finally found.

The above methods are naturally correct, but one problem is low efficiency, and it depends on luck. With luck, one can find them.

Here is a tried and tested analysis method: heating analysis method

Introduction to analytical methods:

The fever analysis method was named by the author himself. If the board is not short circuited to tin, for example, if the chip or capacitor is broken, the GND resistance is generally not 0 Ω, and there will be more or less a few ohms or a few tenths of ohms. By utilizing this feature, it can be quickly located.

Using a DC regulated power supply, adjust the power supply voltage to the voltage of the short-circuit power supply (3.3V for short circuits), set it to the current limiting mode, and the current limiting can be set to 500mA first, depending on the actual situation.

Disconnect the power supply of the PCBA board, connect it to the set power supply, and see where the circuit board gets hot. Generally, where the circuit board gets hot is where there is a short circuit.

You can use an infrared thermal imager to check where it gets hot. Without an infrared thermal imager, you can directly touch it with your hand and feel it (be careful not to burn).

Precautions:

The current limit setting of the DC source needs to be determined based on the actual situation. If the current limit setting is too small, the heating may not be obvious and the problem cannot be found. If the setting is too large, it may burn the copper wire on the PCB. You can gradually adjust the current from small to large to find the problem.