MMA125-E-A and MMA140-E-A
Fault symptom
Remedy
Power indicator is not lit,
fan is not working, no
welding output.
A. Make sure power switch is close.
B. Make sure the electric wire net connecting to input cable is working
alright
Power indicator is lit, fan
doesn
’t work, no welding
output.
A. Input cable is possibly connected to 380V power, which causes over
voltage protection circuit is starting. Connect input cable to 220V
power, then restart the machine.
B. Erratic 220V power supply (input cable is too thin and long) or input
cable is connected to electricity network would start overload voltage
protection circuit. Increase section of input cable or tighten input
contact. Turn off machine for 2-3 min and restart it.
C. Turn on and off power switch continuously would start overload
voltage protection circuit. Turn off machine for 2-3 min and restart it.
D. Cables are loosed between power switch and power source board,
tighten them again.
Erratic welding output
current or out of control
of potentiometer.
A. If potentiometer is damaged, replace it.
B. Terminal of output is broken circuit or poor connect.
Fan is working and
abnormal indicator is not
lit, no welding output.
A. Check if components are poor connects.
B. Check if connector of output terminal is break circuit and poor
connect.
C. If green indicator is not lit in assistant power of MOS board, please
connect with seller or our company and replace it.
D. If there is some question in control circuit, please connect with seller
or our company and replace it.
Fan is working and
abnormal indicator is lit,
no welding output.
A. Overload current protection may start, please turn off machine first,
then restart it after abnormal indicator is off.
B. Overheat protection may start, it will become normal in 2-3min
C. Inverter circuit may go wrong. Please disconnect the power supply
plug of the main transformer on MOS board (near fan), then restart
the machine.
a) If abnormal indicator is still lit, that means some fieldistors on
MOS board are damaged. check and replace it.
b) If abnormal indicator is off:
1) Maybe transformer of middle board is damaged, measure
primary inductance value and Q value of main transformer
by inductance bridge.
2) Primary value is parallel circuit, L=1.2-2.0mH, Q>40
If inductance value and Q value is low, replace it.
3) Maybe some of secondary rectifier tube of transformer is
broken, check and replace rectifier tube.
D. Maybe feedback circuit is in fault.
