1. No display failure when the instrument is turned on: when the instrument is turned on, the screen is not displayed and the indicator light is not lit; When the external power supply is connected, the battery voltage is low and the machine is automatically turned off; When there is no external battery, the battery voltage is low, and then it will automatically shut down, even if the machine is charged.
2. Inspection method: If the instrument has no alternating current, check whether the voltage of 12V is low. The fault alarm shows that the low voltage is detected in the output voltage detection part of the power board.