3. Connect the breadboard of the optocoupler to the USB power cable and test the optocoupler with the contact point of the breadboard probe. If the light of the optocoupler breadboard keeps flashing, it means that the optocoupler is in good condition (the brightness of the light may be different from that of the optocoupler). While blinking, it means that the optocoupler is in good condition. Features: 1. Perform a test to confirm that the board being tested is turned off and that the electrolytic capacitors on the motherboard are fully discharged. It is strictly to conduct tests when the motherboard is on. 2. Confirm the PIN1 of the optocoupler (the pin with a small dot on the breadboard also has a corresponding mark 1 pin) 4. Take steps to ensure that the optocoupler breadboard a good contact with the tested optocoupler, Weight: 0.01763698096 pounds, Manufacturer: Faeymth