Lincoln Electric DC-655 service manual Figure F.5 14-PIN Receptacle

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F-20 F-20

TROUBLESHOOTING & REPAIR

FIGURE F.5 – 14-PIN RECEPTACLE

	K=42
A=32	J=31
B=GND	I=41
L	N
C=2	H=21
D=4	G=75
E=77	F=76
	M

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7.Connect a jumper wire from pin C (lead #2) to pin D (lead #4) at the 14-pin receptacle. See Figure F.5. (Or put the Output Terminal Switch in the ON position.) This should ini- tiate machine output at the welding termi- nals. LED 10 on the firing board should now be on. See Table F.1. If LED 10 does not glow when leads #2 and #4 are con- nected together, perform the Internal Trigger Test. The firing board may be faulty.

8.Locate LEDs 1 to 6 on the firing board. See Figure F.4. Each LED should glow with equal brightness.

NOTE: LEDs 1 through 6 indicate that the SCR gate firing signals are being generated by the firing board.

9.Set the Output Control Switch (SW3) in the “Output Control at DC-655” (local) position.

10.Set the Mode Switch (SW2) in a constant voltage (CV) position.

11.Rotate the Output Control Potentiometer (R1). As the pot is turned clockwise, LEDs 1 through 6 should get brighter. As the pot is turned counter-clockwise, the LEDs should get dimmer.

If the LEDs glow and change in brightness equally as the pot is turned, and the prob- lem continues, the SCR bridge may be faulty. Perform the SCR Output Bridge

Test.

If one or two lights stay bright or dim and the others change, this could indicate an open or shorted gate lead or faulty snubber board. Perform the SCR Output Bridge Test. If the Output Bridge and associated gate leads are OK, the firing board may be faulty.

If all of LEDs 1 through 6 do not glow or do not change in brightness equally as the output control is rotated, go to step 12.

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IDEALARC DC-655