5-95
5 Troubleshooting
NJ-series CPU Unit Hardware User’s Manual (W500)
5-2 Troubleshooting
5
5-2-5 Troubleshooting Errors That Are Not in the CPU Unit
7 Abnormal operation
occurs for the input
points for the same com-
mon (8 or 16 points).
1. Loose screws on the common termi-
nal
Tighten the screws.
2. Faulty contact on the terminal block or
connectors
Replace the terminal block or
connector.
3. Faulty circuits in the Input Unit Replace the Input Unit.
4. Faulty CPU Unit Replace the CPU Unit.
8 The input operation indi-
cators do not light even
though operation is nor-
mal.
Faulty LEDs or LED circuits Replace the Input Unit.
Output Units
No. Abnormal condition Cause Correction
1 None of the outputs turn
ON.
1. The load power is not supplied. Supply power.
2. The load power supply voltage is low. Maintain the power supply volt-
age within the rating.
3. Loose screws on the terminal block Tighten the screws.
4. Faulty contact on the terminal block or
connectors
Replace the terminal block or
connector.
5. The fuse in the Output Unit has burned
out due to overcurrent, e.g., from a load
short-circuit. (You can confirm the fuse
status on a fuse indicator for some Out-
put Units.
Replace the Unit.
6. Faulty contact on Unit connector Replace the Output Unit.
7. Faulty output circuits Replace the Output Unit.
8. Load short-circuit protection has oper-
ated. (You can confirm this on an indica-
tor.)
Check the load.
Check the output wiring.
2 None of the outputs turn
OFF.
Faulty output circuits Replace the Output Unit.
3 A specific output does
not turn ON and the
operation indicator does
not light.
1. The output ON time is too short in the
user program.
Correct the user program to
make a longer output ON time.
2. The output bit is used in more than one
Out instruction in the user program.
Correct the user program so that
only one Out instruction controls
the output bit.
3. Faulty output circuits Replace the Output Unit.
4 A specific output does
not turn ON, but the
operation indicator is lit.
1. Faulty output device Replace the device.
2. Output wiring is broken. Check the output wiring.
3. Loose screws on the terminal block Tighten the screw.
4. Faulty contact on the terminal block or
connectors
Replace the terminal block or
connector.
5. The relay is faulty for a Relay Output
Unit.
Replace the Output Unit.
6. Faulty output circuits Replace the Output Unit.
5 A specific output does
not turn OFF, but the
operation indicator is
not lit.
1. The output relay is faulty for a Relay
Output Unit.
Replace the Output Unit.
2. The leakage current or residual volt-
age prevents resetting.
Replace the external load or add
a dummy resistor.
No. Abnormal condition Cause Correction
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