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Troubleshooting Section 7-1
7-1 Troubleshooting
When a fault relating to the operation of the NT631/NT631C occurs, find the
symptoms in the table below and respond by following the corresponding
Remedy indicated in the table.
Note 1. Confirm system safety before turning the power ON/OFF or resetting.
2. Do not disassemble the PT for repair or modification.
NT631/NT631C
Symptoms
Cause Remedy
Power LED fails to come
ON
Power is not being supplied. Check the connections and make sure that power is
supplied correctly. (3-1-3 Power Supply Connection,
page 33)
Power supply fuse has blown. Contact your OMRON service center.
Nothing is displayed on the
screen.
Screen No. 0 has been read at the
host side.
This is not an error. Change the screen number from
screen number 0. (Setting the screen number to 0
turns the screen off.)
The system startup waiting time has
not elapsed yet.
This is not an error. The display will appear after the
waiting time has elapsed.
Cannot communicate with
the Support Tool
The Transmit mode has not been
established.
Display the System Menu and select the Transmit
mode. (6-6 Transmitting the Screen Data)
Not connected to the Support Tool. Check the installation of the connector cable. (3-2
Connecting to the Support Tool)
The PT model setting and direct con-
nection setting at the Support Tool do
not match the NT631/NT631C.
Using the PT Configuration settings of the Support
Tool, set the PT model and direct connection settings
that match the NT631/NT631C.
Cannot communicate with
the host
Cannot switch from the
system initializing screen.
Communications error
message is displayed
when communicating to
the host.
Memory switch settings do not match. Check the communications setting in the Memory
Switch menu of the Maintenance mode, and match
the communications protocol settings for the host and
NT631/NT631C. (6-7 Setting Conditions for Commu-
nications with Host by Using Memory Switches)
NT631/NT631C and host are not cor-
rectly connected.
Check that the type, length, and installation of the
connector cable match the specifications. (SECTION
4 Connecting to the Host from the RS-232C Port, and
SECTION 5 Connecting to the Host from the RS-
422A/485 Port)
In an RS-422A/485 connection, the
terminator setting is incorrect.
Make the NT631/NT631C and PLC termination resis-
tance settings correctly. (SECTION 4 Connecting to
the Host from the RS-232C Port, and SECTION 5
Connecting to the Host from the RS-422A/485 Port)
In an NT link (1:N) connection, there
is duplication in the unit numbers.
Make the settings again so that there is no duplica-
tion. (6-7-4 Setting the NT Link (1:N) Method (Stan-
dard/High-speed), page 158)
The power to the NT631/NT631C, NT-
AL001 or host is OFF.
Check the power supply.
The buzzer has sounded
and the RUN LED is OFF.
Malfunction due to external noise Carry out grounding work in accordance with the
conditions by referring to 3-1-4 Grounding, page 34.
The NT631/NT631 has developed
trouble.
Contact your OMRON service center.
The touch panel does not
respond.
Malfunction due to external noise Carry out grounding work in accordance with the
conditions by referring to 3-1-4 Grounding, page 34.
The touch panel is broken. Test the touch panel with I/O Check in the MAINTE-
NANCE MODE menu. If there is an error, contact
your OMRON service center.
The PLC mode has
changed to the monitor
mode.
The NT631/NT631C changes the
mode when Host Link communica-
tions are used.
This is an NT631/NT631C specification. When using
a PLC that can also be connected using the NT link
method, use an NT link connection (there is no mode
change with the NT link method).