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F-29

TROUBLESHOOTING & REPAIR

 

ACTIVE SCR TEST (continued)

REMOVE PLUGS J10 & J13

PROTECTION/SNUBBER

L9255

J10

J11

J12

J13

J14

J15

FIGURE F.13 - PROTECTION/SNUBBER BOARD PLUG LOCATIONS.

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TEST PROCEDURE

1.Remove main supply power to machine

2.Remove plugs J10 and J13 from protec- tion/snubber board. See Figure F.13.

3.Remove red insulating paint from heat sink test points. See Figure F.14. DO NOT DISASSEMBLE THE HEAT SINKS.

4.Perform test procedure as outlined in Figure F.15. Repeat test for all four SCR’s

5.Replace any SCR assembly that does not pass test in Step 4

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SCR3

CATHODE

SCR2

SCR4

ANODE

CATHODE

ANODE CATHODE

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SCR1(3 & 4) (1 & 2)

ANODE

PLUG

P10

FIGURE F.14 - SCR TEST POINTS.

SQUARE WAVE TIG 255

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Lincoln Electric SVM100-A service manual Active SCR Test, Figure F.13 PROTECTION/SNUBBER Board Plug Locations