Lincoln Electric SQUARE WAVE TIG 355 Service Manual page 85

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• If 120 VAC is present when the Start button is
held in but the contactor does not stay activated
when the button is released, check the CR1
interlock, the power Start/Stop pushbutton, and
associated circuitry.
Contactor (CR1) Simplified Control Circuit. Also
perform the Control Board Test.
Test for Contact Continuity
1. Remove ALL input power to the machine.
2. Perform the Power
Discharge Procedure.
3. Locate the two leads, #243 and #244, connect-
ed to the input contactor coil. See Figure F.6.
4. Use the external 120 VAC supply to apply
power to the input contactor coil.
• If the contactor does NOT activate, it is faulty.
Replace.
• If the contactor does activate, check the con-
tinuity across the contacts. A normal reading
should be zero ohms or very low ohms.
• If the resistance is high, the contactor is
faulty. Replace.
5. With the contactor NOT activated, check the
continuity across the contacts. See Figure F.6.
• If the resistance is infinite or very high across
the contacts, the contactor is good.
• If the resistance is low, the contactor is faulty.
Replace.
6. After the tests are completed and the problem
repaired, install the machine sides and top,
using the 5/16" nutdriver.
TROUBLESHOOTING AND REPAIR
INPUT CONTACTOR TEST (continued)
See Figure F.6, Input
Factor Capacitor
SQUARE WAVE TIG 355
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