Lincoln Electric IM420-D Machine has maximum output but, Not control, Control, Output, Machine1

E-3	TROUBLESHOOTING	E-3
	Observe all Safety Guidelines detailed throughout this manual

PROBLEMS

(SYMPTOMS)

POSSIBLE

CAUSE

RECOMMENDED

COURSE OF ACTION

Machine has maximum output but	1.	Output control switch (SW3) in wrong	1.	Check position of switch.
not control.		position.
	2.	Output control switch faulty.	2.	Check switch and replace if faulty.
	3.	Open in feedback circuitry.	3.	Check wiring and control and firing
				circuit P.C. board wiring harness
				plugs.
	4.	Faulty control or firing circuit P.C.	4.	All light emitting diodes must be lit,
		boards.		except LED4 on the control/fault
				board. See P.C. board troubleshoot-
				ing guide.
	5.	Output control potentiometer circuit	5.	Check and replace potentiometer if
		open (Lead 75).		faulty. Check wiring of Lead #75.
Machine has minimum output and no	1.	Terminals 73, 74, 75, 76 or 77	1.	Check 73, 74, 75, 76 or 77 for ground
control.		grounded to positive output.		to positive output circuit.
Machine does not have maximum	1.	One input fuse blown.	1.	Check and replace if blown after
output.				checking for reason for blown fuse.
	2.	One phase of main transformer open.	2.	Check for open and repair.
	3.	Faulty control or firing circuit P.C.	3.	All light emitting diodes must be lit on
Machine has output but trips off		boards.		both P.C. boards, except LED4 on
immediately when wire feed unit				control/fault board. See P.C. board
start button is pressed.				troubleshooting guide.
	4.	Output control potentiometer defec-	4.	Check and replace if faulty.
		tive.
	5.	Output control potentiometer leads	5.	Repair.
		open - 76, 77, 226, 236, 237, 238.
Variable or sluggish welding arc.	1.	Machine has either an internal or	1.	Check internally and externally for
		external short circuit on the output.		any shorts and remove or repair.
	2.	Faulty control P.C. board.	2.	Replace control board. See P.C.
				board troubleshooting guide.
	3.	Terminals 73, 74, 75, 76, 77 ground-	3.	Check for grounded 73, 74, 75, 76,
		ed to negative output terminal.		77.
Machine will not shut off.	1.	Poor work or electrode connection.	1.	Check and clean all connections.
	2.	Welding leads too small.	2.	Check table in instruction manual.
	3.	Welding current or voltage too low.	3.	Check procedures for recommended
				settings.
	4.	Defective main SCR bridge.	4.	Check and replace if defective.
Output control not functioning on the	1.	Input contactor contacts frozen.	1.	Check and replace if necessary.
machine(1).	2.	Faulty 2CR relay.	2.	Check and replace if necessary.

(1)If connected to an LN-9 or NA-5, disconnect leads 73, 74, 75 before troubleshooting.

CAUTION

If for any reason you do not understand the test procedures or are unable to perform the tests/repairs safely, contact your Local Lincoln Authorized Field Service Facility for technical troubleshooting assistance before you proceed.

IDEALARC® DC-1000