2--Stroke / 4--Stroke; Burn--Back Time - ESAB MEK 4 Service Manual

6 2- - stroke / 4- - stroke
2--stroke
When switch SA01 is open, 2- -stroke control mode is selected. This means that
closing the welding gun trigger switch starts the wire feed motor, opens the gas valve
and closes the power unit contactor.
Releasing the switch stops the motor, releases the contactor and closes the gas valve.
If crater filling and/or burn- -back time are operative, they will be activated before
welding ceases.
4--stroke
When switch SA01 is closed, 4- - stroke control mode is selected. This means that
first closure of the trigger switch operates the gas valve, with the wire feed motor
starting, and the power unit contactor operating, when the trigger switch is released.
Closing the trigger switch for the second time stops the motor and de- - energises the
contactor in the power unit. Releasing the switch closes the gas valve.
If crater filling and/or burn- -back time are operative, they will be activated before
welding ceases.
7 Burn- - back time
The burn- -back time is the time from when motor braking starts until the machine
contactor opens. It can be adjusted by potentiometer RP03 between 0 and 0.5
seconds.
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