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MELSEC-Q
11 TROUBLESHOOTING
11 TROUBLESHOOTING
This section describes the various types of trouble that occur when the system is
operated, and causes and remedies of these troubles.
11.1 Troubleshooting Basics
In order to increase the reliability of the system, not only highly reliable devices are
used but also the speedy startup of the system after the occurrence of trouble
becomes an important factor.
To start up the system speedily, the cause of the trouble must be located and
eliminated correctly.
The basic three points that must be followed in the troubleshooting are as follows.
(1) Visual inspection
Visually check the following.
1) Movement of sequencer (stopped condition, operating condition)
2) Power supply on/off
3) Status of input/output devices
4) Power supply module, CPU module, I/O module, intelligent function module,
installation condition of extension cable
5) Status of wiring (I/O cables, cables)
6) Display status of various types of indicators ("POWER" LED, "RUN" LED,
"ERR." LED, I/O LED)
7) Status of setting of various types of set switches (Setting of No. of stages of
extension base unit, power interrupt hold-on status)
After confirming items 1) to 7), connect the GX Developer, and check the
operating conditions of the PLC and the contents of the program.
(2) Check of trouble
Check to see how the operating condition of the PLC varies while the PLC is
operated as follows.
1) Set the RUN/STOP switch to STOP.
2) Reset the trouble with the RESET/L.CLR switch.
3) Turn ON and OFF the power supply.
(3) Reduction in area
Estimate the troubled part in accordance with items (1) and (2) above.
1) PLC or external devices
2) I/O module or others
3) Sequence program
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