11. TROUBLESHOOTING
11 - 1
MELSEC-
11. TROUBLESHOOTING
This chapter describes various procedures for troubleshooting, and corrective
action.
11.1 Basic Troubleshooting
System reliability depends not only on reliable equipment but also on short down-
times in the event of faults.
The three basic points to be kept in mind in troubleshooting are :
(1) Visual checks
Check the following points
(a) Machine motion (in the stopped and operating status)
(b) Power ON or OFF
(c) Status of I/O equipment
(d) Condition of wiring (I/O wires, cables)
(e) Display status of various indicators (such as the POWER LED, RUN
LED, ERROR LED, and I/O LED)
(f) Status of various setting switches (such as extension base and power
interruption compensation)
After checking (a) to (f), connect the peripheral equipment and check the
running status of the PLC CPU and the program contents.
(2) Trouble check
Observe any changes in the error condition when performing the following
operations :
(a) Set the RUN/STOP keyswitch to the STOP position.
(b) Reset using the RUN/STOP keyswitch.
(c) Turn the power ON and OFF.
(3) Narrow down the possible causes of the trouble :
Deduce where the fault lies, i.e :
(a) Inside or outside the PLC CPU.
(b) In the I/O module or another module.
(c) In the sequence program.
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