ESAB LAW 400, Service Manual

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+12V
Power supply to the display board and for loss of voltage detection.
See also Items 2 and 13 below.
+15VB
Power supply to circuits that are galvanically or high-- resistance separated from
other electronics on the circuit board.
+/--15V
Internal power supply for the circuit board.
+25VC
Internal power supply for the circuit board, protected by a PTC resistor, R150.
The resistance value of this resistor increases in the event of current overload.
2
DISPLAY OUTPUT
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Outputs G1 -- G3 are used for serial data transfer of the welding current and arc
voltage to a digital display instrument, which may be fitted either in the power unit
or in the wire feed unit. The instrument is described in the service manuals for the
wire feeders MEK 4/4S/4SP.
Outputs G4 and G5 12 V to the instrument. This supply is protected by
PTC resistors R155 and R154. The resistors protect the circuit board against short
circuits to arc voltage or against other voltages occurring in the control cable to the
wire feed unit.