Lincoln Electric SQUARE WAVE TIG 355 Service Manual page 84

F-32
PROCEDURE
1. Remove input power to the machine.
2. With the 5/16" nutdriver, remove the machine
top and sides.
3. Locate the two leads, #243 and #244, connect-
ed to the input contactor coil. See Figure F.5.
4. Connect the volt/ohmmeter to the leads.
WARNING
ELECTRIC SHOCK can kill.
• With input power ON, there
are high voltages inside the
machine. Do not reach into
the machine or touch any
internal part of the machine
while power is on.
TROUBLESHOOTING AND REPAIR
INPUT CONTACTOR TEST (continued)
FIGURE F.5 – INPUT CONTACTOR TEST POINTS
243
244
SQUARE WAVE TIG 355
WARNING
ELECTRICAL ARCING can injure.
• Never mechanically close the contactor with
input power (line voltage) applied and the
machine contactor cover removed.
5. Turn on input power to the machine and press
the Start button.
6. Check for 120 VAC at the contactor coil leads.
• If 120 VAC is NOT present when the Start button
is pressed, check the normally closed (NC) sec-
ondary thermostat, the power Start/Stop push-
button and associated circuitry. See Figure F.6,
Input Contactor (CR1) Simplified Control Circuit.
Also perform the Pilot Transformer Test.
• If 120 VAC is present and the contactor does not
activate, the input contactor is faulty. Replace.
F-32