Items To Be Checked First - Mitsubishi Electric Melsec QJ71LP21 Reference Manual

8 TROUBLESHOOTING

8.2.1 Items to be checked first

Check item
Monitor the communication status of each station with GX
Developer's network diagnostics.
Is the ERR. LED of the CPU module still lit or flickering?
Is the on/off status of the LEDs on the network module
normal?
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Check the CPU module status of the faulty station, the status of the network
modules, the loop status of each station to search for the location where the
error occurred.
Read the error code using GX Developer, and take proper measures against
the error. (For details, refer to the QCPU User's Manual (Hardware Design,
Maintenance and Inspection).
Check the following when LINK PARA. ERROR occurs.
1) Check whether the starting I/O in the network setting matches the slot
where the network module is installed. (Refer to Section 5.2.1.)
2) Check for consistency in the network type and the station number of the
network module. (Refer to Section 5.1.)
3) Check if the PLC side device ranges in Refresh parameters are within the
ranges set in [PLC parameter] – [Device]. (Refer to Section 5.7.2 (2).)
If refresh parameters have not been set, set them according to the
changes made in [Device] under [PLC parameter]. (Refer to Section
5.7.2 (3).)
4) When the Redundant CPU is installed, check whether the host station is
set to be paired. (Refer to Section 7.10.3.)
5) Check whether the network type of the control station matches that of the
normal stations. (Refer to Section 5.1.)
6) When the MELSECNET/H Extended mode has been set, check whether
a compatible network module is used. (Refer to Section 2.2.)
7) When the MELSECNET/H twisted bus system is configured, check that
the MNET/10 mode is not selected as the network type and either of the
forward loop and reverse loop test is not selected as the mode.
Check the on/off status of the RUN, ERR, L ERR. and other LEDs and
correct the error accordingly.
(Refer to Section 4.2.)
If the T. PASS LED turns on and off and looks unstable, the line status is
assumed to be unstable. Therefore, check the following.
1) Check the connector for loose connection and the cable for a break.
2) Check that the cable used conforms to the specifications.
3) Check that the overall length and station-to-station distance the
specifications.
4) Check that cables are correctly installed.
(Refer to Section 4.6 Cable Connection.)
MELSEC-Q
Checking procedure
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