Electronic testing machine boot shows this situation in 1999, the CPU working frequency (11.0592MHz) is not normal, the replacement of crystal oscillator. If the input voltage of two sensors is too high (usually several millivolts), check whether the sensor is normal. The general data obtained by the multimeter electrical barrier measurement sensor are as follows: the input end is about 405 ω; Output end about 340 ω; The resistance of the two leads on either end and the other is 280 ω. Note: the input and output data of the sensor may vary according to the manufacturer, but the change is in a certain proportion. If the comparison voltage of the two operational amplifiers is abnormal, does the resistance of pin 2 and pin 3 of the measurement amplifier change? If resistance occurs, it should be replaced. If the above conditions are normal, the operational amplifier of the electronic testing machine is damaged and should be replaced. If the 220V voltage of the power supply is unstable, a regulated power supply is required.

If the amplifier output voltage is unstable, replace the amplifier. Check whether the CPU frequency (11.0592MHz) and the voltage are stable or drifting. If there is a virtual welding problem, should be re-welding; If the component performance deteriorates, it should be replaced to check whether the circuit board is damp or greasy, necessary cleaning and drying work. If the power transformer has input and no output, replace the transformer or rewind the transformer; Electronic testing machine if the voltage regulator circuit is not normal, check the corresponding bridge diode and filter capacitor and the corresponding connection line, damaged to be replaced, virtual welding or open should be re-welding. Check if the digital circuit voltage is +5V.