Lincoln Electric SVM100-A service manual Silicon Controlled Rectifier Test, Battery Test

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TROUBLESHOOTING & REPAIR F-30

ACTIVE SCR TEST (continued)

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.

FIGURE F.15 - SILICON CONTROLLED RECTIFIER TEST SETUP.

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SILICON CONTROLLED

RECTIFIER TEST

(Heat Sink Mounted Units)

To test SCR’s construct the circuit outlined in Figure F.15. One 6V lantern battery can be used. Resistor values are Ò10%. The voltmeter scale should be low, approximate- ly 0-5 or 0-10 volts.

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.

1.Connect SCR into the test circuit as shown (A) lead to anode (C) lead to cathode and (G) lead to the gate.

2.Close switch SW-1 (switch SW-2 should open), voltmeter should read zero. If the voltmeter reads higher than zero the SCR is shorted.

3.With switch SW-1 closed, close switch SW-2 for two seconds and release. The voltmeter should read 3 to 6 volts before and after switch SW-2 is released. If the voltmeter does not read, or reads only while SW-2 is depressed, the SCR or battery is defective (repeat Battery Test Procedure).

4.Open switch SW-1, disconnect the gate lead (G) and reverse the (A) and (C) leads on the SCR. Close switch SW-1. The voltmeter should read zero. If the voltage is higher than zero, the SCR is shorted.

12/95 SQUARE WAVE TIG 255