Mitsubishi PLC repair example
Model: Mitsubishi PLC
Maintenance: Open the machine inspection, found that the power is burned, it is estimated that the power supply is burned out easier to repair, rectifier electrolytic capacitor after the filter bridge has been blown open, the fuse burned black, check with a multimeter, explosion filter capacitor has been short circuit. Open the fuse, check other components one by one and found no burnout. After replacing the fuse and filter electrolytic capacitor, turn on the power. Measure the power of each group is normal. Install the positive machine, the power supply indicator light is on, and the input point is shorted to the common terminal. When the light is on, the corresponding output light is also on, and it is basically normal. Finally, the computer is used by Eurowork to verify that everything is normal.
Mitsubishi servo amplifier repair example
Model: MR-SA502

Maintenance: First open the lid to see, there is no obvious burned place. Then connect the U · V · W of the servo amplifier to each other. R · S · T must be stepped down from the three-phase 380V to three-phase 220V. Connect the G1 and G2 encoder sockets to the servo motors. Check the correct power after the test, according to the instructions to test the test machine, when the SW5 1 dial to open, immediately hear the relay pull off again, the alarm AL32, check the instructions for the over-current alarm. Because of the multiple servo amplifiers of this type Mitsubishi, in order to achieve fast stability, the two line RF08C and RF81 of the faulty machine were respectively put back to the normal machine tester, and everything was normal. Prove that the base is faulty, and then repair the base; use a multimeter to measure the rectifier bridge, normal, disconnect the output module. The circuit was measured with a multimeter and it was found that there was a breakdown of the output of one module and the negative of the current. On another Mitsubishi servo amplifier of the same model, remove a good module and put it back on the maintenance machine. Check whether there is any error in the connection after connecting it. Finally, power on the test machine. The servo motor is running normally. Then try forward, reverse, and fast. And slow all OK , this time, this machine fault has been ruled out.

SIEMENS 6SE3114 Repair Example
Symptoms: There is no response when the power is turned on, and the 560V DC power supply is normal, and the switching power supply has no output.
Check the idea: This machine adopts UC3844 as PWM modulation, which drives the output of high-power switch FET and checks the decoupling capacitor C56 for slight leakage. After the replacement, the tester is all normal. Because the leakage current of the C56 bypasses part of the operating power supply of the UC3844, and the power supply current limit resistor value is relatively large (1M), the UC3844 cannot reach the start threshold and misdetects it as the undervoltage without starting up.

Universal transmission 5.5KW
Symptoms: There is no sign of power on when the power is turned on.
Troubleshooting: This fault may be a power failure of the CPU itself.
Open the cover and find that the integrated high-power module with rectification and output has a cracking phenomenon. This is caused by man-made damage. There are no scorch marks, but the internal multiple connections have been cut off and damaged and cannot be reused. Power on again after switching to a MUBW15-12A7 and EPERR appears. It seems that this is the real first failure. It should be a memory problem. Normal after replacing AT89C56.

Siemens inverter power supply repair case
Symptoms: When the Siemens inverter power supply is cold, it takes a few minutes before it starts up. When the thermal engine starts, it can start immediately.

Inspection and analysis: This power supply is controlled by UC3842. It can be started to show that the components are not bad, but the performance may be degraded. After the measurement, the capacity of the electrolytic capacitor of the UC3842 power supply terminal becomes less, and the new electrolytic capacitor is replaced with a new one.

Continental 590 DC Governor Repair Case
Fault phenomenon: Continental 590 DC speed controller can not speed.

Inspection and Analysis: After checking the +10V voltage reference power supply is about 2V, -10V voltage reference power supply is about -7V, check that there is a large IC heat, after the replacement -10V power supply is normal, but the +10V power supply is +13V, and then measure this IC There are 2 chip resistors blown in the vicinity. After the replacement, the power of ±10 is normal, and the speed of the motor test is normal.

East yuan servo controller repair two cases
Fault phenomenon: TECO servo controller main board cold is normal, after a period of time the yuan display, but the indicator light is bright.

Inspection and analysis: Normally, the cold machine is normal and the heat engine is not normal, indicating that the components are basically normal, but some of the devices may not be able to perform. The greatest possibility is the leakage of the electrolytic capacitor, which makes the 5V power supply unstable. After checking the factory date of this machine for more than ten years, More than 10 years of electrolytic capacitors are prone to failure. Replace all new electrolytic capacitors and repeat the test.

Fault: TECO servo controller displays “AL-15” alarm and no output is started.

Analysis: Check the “AL-15” alarm for overcurrent (software). After checking that both current transformers are normal, try to screen the alarm output terminal of the smart module and it is also invalid. The trigger module can normally turn on and off. Another motherboard is replaced, the power display is not normal, the starting output is unstable in one direction, and the other direction is jittery. Then check that one of the input terminals of the module has a much lower resistance value than the other input terminals. The optocoupler is not normal. Check to make sure that there is a problem with the optocoupler and it is normal to replace the optocoupler.

Lenze servo controller shows over-current
Fault phenomenon: Lenze servo controller shows over-current.

Inspection and analysis: Normally caused over-current with true over-current and false over-current. The reason for true over-current is that IGBT is bad and over-current is formed due to short-circuit caused by three-phase output and DC bus. The second case is the overcurrent due to the short circuit between the three phases of the output. The third situation is that the trigger circuit is abnormal and the output is unbalanced, resulting in overcurrent. The cause of false over-current is that the current transformer is bad and causes the detection error, and some circuit optocoupler is bad and the detection signal cannot be transmitted and the over-current is also displayed.

After measuring the IGBT is bad, the voltage regulator diode of the driver circuit has been burned out, and the replaced component load tester runs normally.

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