10 - 17
10   Troubleshooting and Maintenance
OMNUC G5-series (Pulse-train Input Type) AC Servomotors and Servo Drives User’s Manual
10-4  Troubleshooting
10
10-4-2  Error Diagnosis Using the Operation State
10-4-2 Error Diagnosis Using the Operation State
Symptom Probable cause Check items Measures
The PWR indicator 
does not light 
when the Servo 
Drive is powered 
on.
The power supply wiring is 
incorrect.
Check to see if the power supply input 
is within the allowed power supply 
voltage range.
Supply the correct power 
supply voltage.
Check to see if the power supply input 
is wired correctly.
Wire correctly.
The Servomotor 
does not rotate 
when a command 
is input from the 
controller.
The Operation Command 
(RUN) signal is OFF.
Check in the monitor mode if the RUN 
signal turns ON/OFF.
• Input the Operation 
Command (RUN) signal.
• Wire correctly.
Forward Drive Prohibition 
Input (POT) or Reverse 
Drive Prohibition Input 
(NOT) signal is OFF.
Check in the monitor mode if the POT 
and NOT signals turn ON/OFF.
•
Turn ON the POT or NOT signal.
•
Disable the parameter if the 
POT or NOT signal is not used.
The control mode does not 
conform to the command.
Check the value set in Control Mode 
Selection (Pn001).
Set the control mode according 
to the command.
The Error Counter Reset 
Input (ECRST) signal is ON.
Check in the monitor mode if the 
ECRST signal turns ON/OFF.
• Turn OFF the ECRST signal.
• Wire correctly.
The value set in Command 
Pulse Mode Selection 
(Pn007) is incorrect.
Check the command pulse type of the 
controller and that of the Servo Drive.
Set the command pulse type of 
the Servo Drive so that it 
matches the command pulse 
type of the controller.
The Zero Speed 
Designation Input (VZERO) 
signal is OFF.
Check in the monitor mode if the 
VZERO signal turns ON/OFF.
• Turn ON the VZERO signal.
• Wire correctly.
No internally set speeds are 
set.
Check the values set in Pn304 to 
Pn311.
Set the desired rotation speed.
The values set in No.1 Torque 
Limit (Pn013) and No.2 
Torque Limit (Pn522) are 0.
Check the values set in Pn013 and 
Pn522.
Restore the default set values.
The Servomotor power 
cable is wired incorrectly.
Check the wiring. Wire correctly.
The encoder cable is wired 
incorrectly.
The control I/O connector 
(CN1) is wired incorrectly.
Check the command pulse wiring. Wire correctly.
Check the command pulse type. Set the command pulse type of 
the Servo Drive so that it 
matches the command pulse 
type of the controller.
Check the command pulse voltage. Connect resistors appropriate 
for the voltage.
Power is not supplied. Check the power supply and the PWR 
indicator.
Turn ON the power supply.
Check the voltage across the power 
terminals.
Wire the power-on circuit 
correctly.
The speed command is 
disabled.
Check to see if the speed command 
input method is correct.
• Set the internal speed 
correctly.
The torque command is 
disabled.
Check to see if the torque command 
input method is correct.
Set the torque command 
correctly.
Both the CW and CCW 
inputs are turned ON 
simultaneously.
Check the command pulse wiring. • Input the pulse signal to 
either the CW or CCW input.
• Unused input terminals must 
be always OFF.
The Servo Drive is faulty. – Replace the Servo Drive.