Lincoln Electric SVM144-B service manual Figure F.7 Location Leads X2

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F-25 TROUBLESHOOTING & REPAIR F-25

ACTIVE SCR RECTIFIER ASSEMBLY TEST (continued)

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6.Disconnect leads X2 and X3 (braided copper strap) from the negative capaci- tor bank buss bar using a 1/2 in. open end wrench. See Figure F.7.

FIGURE F.7 — LOCATION OF

LEADS X2 AND X3.

NEGATIVE

CAPACITOR

BANK BUSS

BAR

8.Use a commercial SCR tester or con- struct the tester circuit shown in Figure F.8. One 6-volt lantern battery can be used. R1 and R2 resistor values are ±10%. Set voltmeter scale low, at approximately 0-5 volts or 5-10 volts.

a.Test the voltage level of the battery. Short leads (A) and (C). Close switch SW-1. Battery voltage should be 4.5 volts or higher. If lower, replace the battery.

FIGURE F.8 — SCR TESTER CIRCUIT

AND SCR CONNECTIONS.

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LEADS X2 AND X3

CONNECTION

7. Separate leads X2 and X3 from the negative capacitor bank buss bar. Be sure there is no electrical contact.

NOTE: DO NOT DISASSEMBLE THE SCR

RECTIFIER HEAT SINK ASSEMBLY.

POWER MIG 255