Printing machine electrical troubleshooting three
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First, BISHENG WD-E offset press
Symptom: Start the machine and find that the I-ink roller does not turn.
Analysis and overhaul: Open the side door of the machine (four sets of water and ink speed control devices are installed), and find that the red light of one of the speed regulating circuit boards is bright (indicating a fault), and touch the end of the rotor shaft exposed at the end of the motor by hand. - Really did not turn. Considering that the machine is a newly introduced machine and there is no speed control circuit board, it is only possible to change the test motor to determine the fault point. Shut down and insert the motor into the power line plug of the II ink motor. Test machine: II ink motor runs normally, and the original red light speed control circuit board has returned to a bright green light (normal state); but the I ink motor still does not turn, and the corresponding speed control circuit board lights up red light , indicating that the fault is caused by the damage of the I-Motor motor (but the actual data of the two motors is not found.) When the power is turned off, the I ink motor is removed together with the speed reducer, and then replaced with a new set of ink glue motor, and then the plug itself is restored. Power-on test machine: I ink and II ink motor are all running normally. Why should the fault be removed together with the speed reducer? The main reason is that if the motor is replaced by a single motor, if the motor and the speed reducer cannot be accurately assembled in place, it is easy to cause the motor to have a poor or unsmooth failure during operation, and the time is long and the motor is easily damaged.
Second, JS2102 offset press
Symptom 1: In normal printing, the counter suddenly does not count.
Analysis and overhaul: After detection, the transistor that sends the counting signal to the counter is close to the constant output of the switch (normally, the iron piece that is synchronous with the machine should pass (block)) (transistor proximity switch), and the transistor is close to the switch. Once it is turned on, the iron piece is turned off and turned off - the pulse signal is sent and the counter can count. Power off, After the transistor is removed from the proximity switch, it is checked: no open circuit of the oscillating coil or defective solder joints of some components is found. Another power supply is re-tested: the output is terminated by the iron plate, and the output terminal has a constant output; and the multi-meter DC voltage file is used to measure the trigger voltage sent by the front-end circuit between the control electrode and the cathode of the thyristor. Should not be turned on. It is then suspected that there is leakage between the anode and cathode of the thyristor. When the power is turned off, the thyristor is soldered with an electric soldering iron, and then the multimeter resistance is used to detect that there is no leakage between the anode and the cathode. But I feel that since the leakage is there, it should be that the main circuit still has problems! The rectifier power supply circuit was further tested with a multimeter resistance file, and one of the rectifier diodes was found to have broken down. After switching to a new rectifier diode of the same type, try again and troubleshoot.
Symptom 2: During normal printing, the machine suddenly drops from high speed to low speed and even stops.
Analysis and overhaul: After observation, it was found that after the shutdown, the prime mover of the electromagnetic speed-regulated asynchronous motor, the AC motor, was still in normal operation, but the slip clutch did not rotate. Explain that the problem is in the slip clutch. However, when the indicator light on the panel of the control box is lit, it indicates that the DC main circuit is good, and the fault is in the control circuit. Power off, the control box is removed, and the parameters of the main transistors are detected by the multimeter resistance file: it is found that the three electrodes of BG3 (triode) and BG4 (single junction transistor) are not electrically connected to each other, indicating that the two tubes are The internals have been blown (of course, no pulse can be sent to trigger the thyristor operation of the main circuit). Replace all these two tubes, test the machine: the machine still does not turn. Using the multimeter DC voltage to detect the BG3 and BG4 tube operating voltage values are very low, the voltage value between the 3 and 1 legs of the NE555 integrated block is also very low; re-measure their power supply: R2 (resistance) of the terminal voltage is 15V, the output voltage is 14V, obviously it is far from the 24V voltage value that can be provided by the power transformer secondary (boosted by diode half-wave rectification and capacitor filtering)! Power off, unplug the control circuit board, and solder several filter capacitors connected in parallel with the power supply to detect with the multimeter resistance file (when they deteriorate, the output voltage will drop): The charging and discharging performance is normal, indicating that there is no problem. Power-on: Use the multimeter AC voltage to measure the secondary voltage of the transformer in the main circuit board to 24V, normal. This clearly shows that the fault is caused by one or both of the power supply regulators (V15 and V16). However, the actual control circuit board does not have these two voltage regulators (the attached schematic does not match the actual map). Therefore, it can only be traced and searched: it is found that the 7815 three-terminal regulator is used to replace the two voltage regulators. After replacing a new 7815 three-terminal regulator and plugging the control board back into place, try again and troubleshoot.