The startup display of the electronic universal testing machine shows that this situation occurred in 1999. It is possible that the CPU working frequency (11.0592MHz) is not normal. Replace the crystal oscillator immediately. If the input voltage of two sensors is too high (usually a few millivolts), should the sensors be checked for normal operation? The general data obtained by measuring the resistance of the sensor with a multimeter is: around 405 Ω at the input end; The output terminal is around 340 Ω; The resistance value between any two leads at one end and the other end is 280 Ω. Attention: The input and output data of sensors may sometimes vary depending on the manufacturer, but the changes have a certain proportion. If the comparison voltage between two operational amplifiers is abnormal, does the resistance of pins 2 and 3 of the amplifier change? If the resistance value occurs, it should be replaced. If all the above conditions are normal, then the operational amplifier of the electronic universal testing machine is damaged and should be replaced. If the 220V voltage of the power supply is unstable due to drift or random jumping of the reading, a stable power supply needs to be configured.

If the output voltage of the amplifier is unstable, replace the amplifier. Check if the CPU frequency (11.0592MHz) and comparison voltage are stable or experiencing drift? If there is a problem of virtual welding, it should be re welded; If the performance of the components deteriorates, they should be replaced and checked for moisture or oil stains on the circuit board. Necessary cleaning and drying should be carried out. If the power transformer has input but no output, replace the transformer or rewind the transformer; If the voltage stabilizing circuit of the electronic universal testing machine is not normal, check the corresponding bridge diode, filter capacitor, and corresponding connecting circuit. If damaged, replace it. If there is a false soldering or open circuit, it should be re soldered. Check if the voltage of the digital circuit is+5V.