The startup of the electronic universal testing machine shows that this situation occurs in 1999. The CPU working frequency (11.0592Mhz) may be abnormal. Replace the crystal oscillator immediately. If the input voltage of the two sensors is too high (usually a few millivolts), check whether the sensors are normal? The general data obtained by measuring the sensor with the resistance block of the multimeter is: About 405 Ω at the input end; The output terminal is about 340 Ω; The resistance of two leads at either end and the other end is 280 Ω. Note: the data at the input and output ends of the sensor sometimes varies with different manufacturers, but the change is in a certain proportion. If the comparison voltage of the two operational amplifiers is abnormal, measure whether the resistance of pins 2 and 3 of the amplifier changes? If the resistance value changes, it shall be replaced. If the above conditions are normal, the operational amplifier of the electronic universal testing machine is damaged and should be replaced. If the voltage of 220V power supply is unstable, a regulated power supply shall be configured.
If the output voltage of the amplifier is unstable, replace the amplifier. Check whether the CPU frequency (11.0592Mhz) and comparison voltage are stable or drift? If there is a problem of false welding, it shall be re welded; If the performance of components becomes poor, they shall be replaced, check whether the circuit board is damp or greasy, clean it if necessary and dry it. If the power transformer has input and no output, replace the transformer or rewind the transformer; If the voltage stabilizing circuit of the electronic universal testing machine is abnormal, check the corresponding bridge diode, filter capacitor and corresponding connecting circuit, replace the damaged ones, and re weld the ones with faulty welding or open circuit. Check whether the voltage of digital circuit is + 5V.