①The display is dim or bright and dark after turning on. First, measure whether the voltage of the battery used is normal. If it is normal, you can further check whether the battery spring pressure is sufficient and whether the contact is good. If there is any problem, you can stretch the spring or use fine sand to polish the contact of the battery pole piece.
②There is a digital display after power-on, but it cannot be calculated. Use a multimeter to check the circuit board to see if there is a short circuit between the terminals of the integrated circuit block. Use a multimeter to check the voltage value of the keyboard input terminal of the integrated block (24-29 pins for L1-3033E chip). The normal value should be about 0.12V, otherwise it may be possible. The manifold is broken. If the voltage is normal, but the operation cannot be performed, it may be due to poor keyboard contact, foreign matter on the circuit board, open circuit on the circuit board, or stuck keys.