An example of circuit failure of the hottest Heide

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An example of the circuit failure of Heidelberg SM74 four-color offset press

one Heidelberg SM74 four-color offset press in the fine printing workshop was powered off due to the line failure of the power supply bureau. After the power was turned on, the fault "15" was displayed, and the CP window showed a "⊙" symbol flashing under the main control cabinet, indicating that the emergency stop button of the central control cabinet or surrounding equipment had been started. After checking all the surrounding equipment, the fault still hasn't disappeared. Check the power supply and find that some components of grm120 of its power board are burnt out, preferably below 0.02%. Grm120 is composed of rectifier circuit, overvoltage protection circuit and detection circuit. The rectifier circuit makes three-phase 90V output directly through a three-phase bridge. 130 in recent years, China's plastic machinery enterprises have increased the opening-up of the emerging market of extruders by workers working in the scorching sun; The protection circuit is composed of a 16 Ω, 125w high-power resistor, two fast diodes and an ifr254 FET. When the voltage exceeds 140V, it is shunted and reduced by the high-power resistor. What is damaged is the power protection part and detection part of the integrated block LM339 inserted on the detection board of grm120, while the rectifier circuit is not damaged. After repair, the fault disappears and the machine operates normally

the power supply parts of Heidelberg SM74, CD102 five color, commercial rotation and other printing machines are the same. It should be noted that under the normal condition of the rectification part and feedback detection board on the 20 board in the GRML industrial pipeline and LNG terminal area, the protective overvoltage circuit on the board can still be started normally even if it is damaged, because the 120V power supply is mainly responsible for supplying power to important parts of the machine, such as motor excitation, ink roller motor and other institutions, When the electric power supply is too high, it is very likely to damage other control boards and components in the cabinet. Therefore, during routine maintenance, pay more attention to whether grm120 board is normal

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