Mitsubishi Electric MELDAS C6 Maintenance Manual page 160

(3) Problems related to remote I/O
The communication alarm LED ALM (red) lights.
Cause
The remote connection cable is
not connected.
The cable is disconnected or has
a connector contact fault.
The remote I/O unit is faulty.
The power system LED POWER (green) turns OFF.
Cause
The input power is not being
supplied.
(The input power is not within the
tolerable range, or the internal
power is faulty.)
(4) Problems related to Ethernet
A communication error message is appeared on the display, and the communication LEDs RX (green)
and TX (green) turn OFF.
In other cases, a communication error message is appeared on the display, and after the OK button is
pressed, the communication error message appears again and the communication LEDs RX (green)
and TX (green) turn OFF.
Cause
The Ethernet cable is not
connected, is broken, or there is
a contact fault at the connector.
A straight type Ethernet cable is
in use.
The Ethernet unit is not inserted
to the very back.
The Ethernet unit is faulty.
CAUTION
Do not apply voltages other than those indicated in this manual on the connector.
Doing so may lead to destruction or damage.
Incorrect connections may damage the devices, so connect the cables to the specified
connectors.
Do not connect or disconnect the connection cables between each unit while the power is ON.
Do not connect or disconnect the PCBs while the power is ON.
3. TROUBLESHOOTING
3.2 Troubleshooting
Check the connection of the R211 cable between the NC
control section and remote I/O unit.
Contact the Mitsubishi Service Center, and then replace
the card.
Supply a +24V±5% voltage to the Remote I/O unit.
Check that the input voltage is not +20V or less. If it is
being supplied correctly, contact the Mitsubishi Service
Center.
Check the cable connected between the NC control unit
and display.
Use a cross type Ethernet cable.
Insert the Ethernet unit so that the plate is flush with the
front panel.
Contact the Mitsubishi Service Center and replace the unit.
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Remedy
Remedy
Remedy