1. First of all, understand the specifications of DC plug from the model. DC2.1 refers to the inner diameter of 2.1mm, and DC2.5 refers to the inner diameter of 2.5mm
2. Understand the positive and negative terminals of the DC head from the appearance. At present, the DC head is generally positive with a round hole and a negative outer ring
3. Use a multimeter to verify the polarity. The red marker is the positive pole of the power supply, and the black marker is the negative pole
Post time: Mar-11-2022