ESAB LAW 400, Service Manual

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14 PRESETTTING
Preset XS1;M
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This input is used only when an MEK 4S or MEK 4SP wire feed unit is connected
to the LAW power unit.
The wire feed unit has a switch that the welder uses when he want to see set values
for wire feed speed and voltage instead of measured values of welding current and
arc voltage. When the switch on the wire feed unit is closed, circuit board input H7
is shorted to 0 VB.
Wire feed speed reference XS1;P
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This input is used only when an MEK 4S or MEK 4SP wire feed unit is connected
to the LAW power unit.
The wire feeder sends an analogue wire feed speed signal to the LAW for display in
the digital display.
The input is also used to sense whether an MEK 4S/SP is connected. Scaling of the
voltage reference changes if an MEK 4S/SP is connected, relative to the scaling used
if some other wire feed is connected.
The input on the circuit board is adjusted by means of potentiometer R163 so that a
voltage of 12.40 V at terminal H3 produces a voltage of 5.00

0.005 V across
diode D31.