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MELSEC-Q
10 TROUBLESHOOTING
10.3.1 Troubleshooting when "RUN" LED is turned OFF
Symptom Cause Corrective action MC
Bidirectional
Non
procedure
โข A transmission setting
switch is set to an
unusable position.
โข Set the switch by GX Developer correctly and
after writing to the CPU reset the CPU.
โข PLC CPU error.
โข Remove the cause of the CPU error and reset
the CPU.
Note
โข During the Q series C24 and external device
loopback test, the minimum parameters file
must be written to the CPU beforehand.
โข Power module 5 V
current capacity is
insufficient.
โข Calculate the 5 V current drain of each installed
module. If the current capacity is insufficient,
check power module selection.
Note
โข Whether or not the current capacity is
insufficient can be checked by disconnecting
the expansion base and installing only the Q
series C24 to the basic base.
โข The Q series C24
"RUN" LED turned off.
โข Extraneous noise
caused the Q series
C24 to abnormal
operation.
โข Check if the shield wire is 2-point ground.
โข When ground is used with other devices,
ground the Q series C24 independently.