The simplest and most intuitive way to detect how the switching power supply chip is detected is to measure the input and output voltage values.
First set the multimeter function switch to AC voltage (manual 500V or 750V) to ensure that the input voltage is normal;
Then turn the multimeter function switch to the DC voltage (the manual switch is adjusted to a higher voltage unit according to the marked voltage), measure the output voltage, and it can be considered good if it is consistent with the marked voltage.