Lincoln Electric SP-250 service manual Figure F.7 SCR Tester Circuit and SCR connections

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F-24

TROUBLESHOOTING & REPAIR F-24

ACTIVE SCR RECTIFIER ASSEMBLY TEST

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7.Connect the Tester to the SCR 1 as shown in Figure F.7.

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

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

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

FIGURE F.7 - SCR Tester Circuit and SCR connections.

8. Close switch SW-1.

NOTE: Switch SW-2 should be open.

9.Read meter for zero voltage.

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

10.Close or keep closed switch SW-1

11.Close switch SW-2 for 2 seconds and release and read 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 voltages 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: Be sure battery is functioning properly. A low battery can affect the results of the test. Repeat Battery Test Procedure in Step 6 if needed.

12.Open switch SW-1.

13.Reconnect the Tester leads. See Figure F.7.

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

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

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

14.Close switch SW-1.

15.Read 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.

16.Perform the Active Test Procedure outlined in Steps 5-13for SCR 2.

17.Replace all SCR assemblies that do not pass the above tests.

18.Replace all Molex Plugs onto the Control Board and connect leads X2 and X3.

IDEALARC SP-250