Fangrui Product Details 1, Test To Confirm That The Board Under Test Has Been Powered Off, And The Electrolytic Capacitors Of The Motherboard Days Have Been Fully Discharged. It Is Strictly Prohibited To Test When The Motherboard Is Energized. 2, Confirm The Optocoupler Pin 1 (with A Small Dot On The Foot Test Board Also Has The Corresponding 1 Feet Of The Logo) 3, The Optocoupler Test Board Connected To The Usb Power Cord, The Test Board Probe Contact Need To Test The Optocoupler, If The Optocoupler Test Board On The Light Has Been Blinking, Said The Optocoupler Is Good (the Brightness Of The Light May Not Be The Same As Long As It Is Blinking Means That The Optocoupler Is Good) 4,measurement To Ensure That The Optocoupler Test Board And The Measured Optocoupler Have Good Contact 5, If The Indicator Light Is Often Bright Or Not Bright, The Photocoupler Can Be Removed From The Circuit Board And Inserted Into The Photocoupler Seat Of The Test Board To Reconfirm The Test Results. Applies To 4-pin Optocoupler, Other Types Of Opto