Lincoln Electric SVM188-A service manual Active Test

Return to Section TOC

Return to Section TOC

Return to Master TOC

Return to Master TOC

F-31 TROUBLESHOOTING AND REPAIR F-31

SCR BRIDGE TEST(continued)

FIGURE F.15 – ACTIVE SCR TEST

PROCEDURE

Return to Section TOC

Return to Section TOC

Return to Master TOC

Return to Master TOC

ACTIVE TEST

1.With the circuit shown in Figure F.17. One 6-volt lantern battery can be used. Set the voltmeter scale low, at approximately 0-5 volts or 0-10 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.

2.Connect the Tester to SCR 1 as shown in Figure

F.17.

a.Connect Tester lead (A) to the anode.

b.Connect Tester lead (C) to the cathode.

c.Connect Tester lead (G) to the gate.

3.Close switch SW-1.

NOTE: Switch SW-2 should be open.

4.Check the meter for zero voltage.

a.If the voltage reading is higher than zero, the SCR is shorted.

b.If the reading is zero volts, continue to Step 6.

6.Close switch SW-2 for 2 seconds and release and read the meter.

a.If the voltage is 3-6 volts while the switch is closed and after the switch is open, the SCR is functioning.

b.If the voltage is 3-6 volts only when the switch is closed or there is no voltage when the switch is closed, the SCR is defective.

NOTE: A low battery can affect the results of the test. Repeat the battery test procedure in Step 1 if needed.

7.Open switch SW-1.

8.Reconnect the Tester leads. See Figure F.17.

a.Connect Tester lead (A) to the cathode.

b.Connect Tester lead (C) to the anode.

c.Disconnect Test lead (G) from the gate.

9.Close switch SW-1.

10.Read the meter for zero voltage.

a.If the voltage is zero, the SCR is functioning.

b.If the voltage is higher than zero, the SCR is shorted.

11.Repeat steps 2 through 10 for each SCR.

DC-600