Lincoln Electric SVM169-A service manual Active SCR Test

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F-26 TROUBLESHOOTING & REPAIR F-26

ACTIVE SCR TEST (continued)

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TEST PROCEDURE

1.Remove main supply power to the TIG 185 machine.

2.Locate and remove plug J2 from the control board. See Figure F.3.

3.Perform test procedure as outlined in Figure F.5. Repeat test for all four SCRs. See Figure F.6.

4.Construct the circuit outlined in Figure F.5. One 6V lantern battery can be used. Resistor values are ±10%. The voltmeter scale should be low, approximately 0-5 or 0-10 volts.

5.Battery Test - Check the battery by shorting leads (A) and (C) and then close switch SW-1. Re-place battery if voltage is less than 4.5 volts.

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FIGURE F.5 ACTIVE SCR TEST SETUP

SW1

R2

	V	R1
		SW2
6volt	A	G
Lantern
	SCR
Battery		C
	under
	test
		R1= 4 ohms /10 watts
		R2= 3 ohms/ 10 watts

To test SCRs construct the circuit outlined above. Resistor values are plus or minus ten percent. The voltmeter scale should be low, approximately 0-5 or 0-10 volts DC.

PRECISION TIG 185