Mitsubishi PLC maintenance and fault diagnosis - Solutions - Huaqiang Electronic Network

Brand AVX TPSE226M035R0125 Low impedance tantalum capacitor AVX 22

Electronic scale crystal oscillator 3.2*2.5mm 3225 16M (16.000MHZ) 12PF 10PPM 20PPM 30PPM

SMD aluminum electrolytic capacitor

RF cable can be customized for other specifications

Mitsubishi plc repair:
Inspection method: Turn on the machine check and find that the power supply is burnt out. After the rectifier bridge, the filter electrolytic capacitor has exploded. The fuse burns black. Check with a multimeter. The blasted filter capacitor is short-circuited. The fuse was opened, and other components were found to be burnt out one by one. After replacing the fuse and the filter electrolytic capacitor, the power is measured. The power of each group is normal. Install the whole machine. After the power is turned on, the power indicator light is on, the input point is shorted to the common end, the input light is on, and the corresponding corresponding lighting is also on. Use the system test platform to verify that everything is ok.
PLC troubleshooting:
All brands of PLCs have self-diagnostic functions. When the PLC is abnormal, you should make full use of its self-diagnosis function to analyze the cause of the fault. When an abnormality occurs in the PLC, first check the power supply voltage, the screws and connectors of the PLC and I/O terminals for looseness, and whether there are other abnormalities. Then, according to the indicator status of various LEDs set on the PLC basic unit, check whether the PLC itself and the external are abnormal. When an error occurs, one of the values ​​of 8009, 8060~8068 is written to the special data register D8004. If the content of the write D8004 is 8064, the error code can be known by looking at the contents of D8064. Refer to the error code table in the PLC manual for the actual error contents corresponding to the error code.
The following takes the Mitsubishi FX series PLC as an example to illustrate the method of diagnosing the cause of PLC failure based on the status of the LED indicator.
1. Power indicator ([POWER] LED indication)
When power is supplied to the Mitsubishi PLC basic unit, the [POWER] LED set on the surface of the base unit will light. If the power is turned on but the [POWER] LED does not light, check the power wiring. In addition, if there is a drive sensor or the like on the same power supply, check for load short-circuit or overcurrent. If it is not the above reason, it may be that the conductive foreign matter or other abnormality is mixed in the PLC, so that the fuse in the basic unit is blown, and this can be solved by replacing the fuse.
2. Error indication ([EPROR] LED flashes)
When the program syntax is wrong (such as forgetting to set the timer or counter constant, etc.), or the content of the program memory changes due to abnormal noise, conductive foreign matter, etc., the [EPROR] LED will flash, and the Mitsubishi PLC will be in the STOP state. At the same time, all outputs are turned OFF. In this case, check the program for errors and check for conductive foreign matter and high-intensity noise sources.
3. Error indication ([EPROR] LED is on)
When the Mitsubishi PLC is mixed with conductive foreign matter or is affected by external abnormal noise, the CPU is out of control or the calculation cycle exceeds 200ms, the WDT is faulty, the [EPROR] LED is on, the PLC is in STOP, and all outputs are turned OFF. At this time, the power-off reset can be performed. If the PLC returns to normal, check the presence or absence of abnormal noise sources and conductive foreign matter. In addition, please check if the grounding of the PLC meets the requirements. If the [EPROR] LED is on → flashing changes during the inspection process, please check the program. If the [EPROR] LED remains lit, please check if the program calculation cycle is too long (monitor D8012 knows the maximum scan time). If the [EPROR] LED is still on after the full inspection, you should consider some kind of malfunction inside the PLC. Please contact your service provider.
4. Input indication Whether the input signal switch is actually ON or OFF regardless of whether the input unit's LED is on or off. If the rated current capacity of the input switch is too large or due to oil intrusion, etc., contact failure is likely to occur. When the input switch is connected in parallel with the LED light-on resistor, the input circuit of the Mitsubishi FX series PLC can be input even if the input switch is OFF but the parallel circuit is still turned on. If an input device such as a light sensor is used, the sensitivity may change due to dirt or the like adhering to the light-emitting/light-receiving portion, and the "ON" state may not be fully entered. The input of ON and OFF cannot be received within a short period of time compared to the Mitsubishi FX2N series PLC. If a different voltage is applied to the input terminals, the input circuit will be damaged.
5. Output indication Whether the LED of the output unit is on or off, if the load cannot be turned ON or OFF, it is mainly due to overload, load short circuit or inrush current of the capacity load, etc., causing the relay output contact to be bonded, or the contact surface of the contact is not Good lead to poor contact.