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F-55 F-55
ACTIVE SCR TEST (continued)
FIGURE F.19 - POWER BOARD PLUG LOCATIONS
TROUBLESHOOTING & REPAIR
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.
SQUARE WAVE TIG 355
4
567 3 21
11121314
10 9 8
SQUARE WAVE POWER
G2081-[ ]
J1