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TROUBLESHOOTING & REPAIR
ACTIVE SCR TEST (continued)
FIGURE F.19 - POWER BOARD PLUG LOCATIONS
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SQUARE WAVE POWER
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TEST PROCEDURE
1.Remove the input power to the machine.
2.With the 5/16” nut driver, remove the machine case top and sides.
3.Perform the Input Power Factor Capacitor Voltage Check and Discharge procedure.
4.Remove the output welding cables from the machine.
5.Remove plug J1 from the power PC board. See Figure F.19.
6.Place the polarity switch (S1) in a “DC” position.
7.Remove the red insulating paint from heat sink test points. See Figure F.20. DO NOT DISASSEMBLE THE HEAT SINKS.
8.With the 1/2” wrench, remove the choke lead from the negative plate (top).
9.Perform the test procedure as outlined in Figure F.21. Repeat the test for all four SCRs.
10.Replace any SCR or SCR assembly that does not pass the test in Step 9.
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SQUARE WAVE TIG 355
