User manual

83
Inspection and Maintenance
Inspection and maintenance
Input module
Symptom Possible cause Action
Power supply LED will not
illuminate.
Fuse blows Replace the fuse
Fuse blows frequently. Short circuit or defective part
Replace the power supply or the
CPU module
Run LED will not illuminate.
Program errors Correct the program
Power line defect Replace the CPU module
Output will not turn to On state
during Run.
Short or open circuit Replace the CPU module
I/O modules above a certain
address will not operate.
I/O bus error Replace the backplane module
Input or output module of only
certain address will turn to On
state.
I/O bus error Replace the backplane module
Not all contacts on an output
module operate properly.
I/O bus error Replace the backplane module
Symptom Possible cause Action
No inputs on an input module will
turn On (LEDs are not illuminated).
No external input power Supply power
Low external input voltage Supply rated load power
Loose terminal screw or defective
contact
Tighten the screw and reconnect
the module
Inputs will not turn to On state
(LEDs are illuminated).
Defective input circuit Replace the input module
Inputs will not turn to Off state. Defective input circuit Replace the input module
One or more inputs on an I/O
module will not turn On.
Device connected to the input
module is defective.
Replace the input device
Loose input wiring Reconnect the input wiring
External input time is too short. Adjust the input module
Loose terminal screw or defective
contact
Tighten the screw and reconnect
the module
One or more inputs on an I/O
module will not turn Off.
Defective input circuit Replace the input module
Input changes On/Off state
erratically.
Low external input voltage Supply rated input voltage
Noise error Troubleshoot for noise
Loose terminal screw or defective
contact
Tighten the screw and reconnect
the module
Input display LED will not
illuminate (input is On in PLC).
LED error Replace the input module