Lincoln Electric IM481-B manual Faulty Output Control potentiometer

Trouble		Cause		What To Do
Machine has low output and no con-	1.	Output Control “Local-Remote”	1.	Check position of switch.
trol.		switch (S2) in wrong position.
	2.	Output Control switch faulty.	2.	Check switch and replace if
				faulty.
	3.	Open in feedback circuitry.	3.	Check wiring and control PC
				Board wiring harness plugs.
	4.	Faulty Control PC Board.	4.	Replace. See Procedure for
				Replacing PC Boards.
	5.	Output control potentiometer cir-	5.	Check and replace potentiometer
		cuit open (Lead 75).		if faulty. Check wiring of Lead
				#75.
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	2.	Check for open and repair.
		open.
	3.	Faulty Control PC Board.	3.	Replace. See Procedure for
				Replacing PC Boards.
	4.	Output control potentiometer	4.	Check and replace if faulty.
		defective.
	5.	Output control potentiometer	5.	Check and repair broken leads.
		Leads 210, 211, or 75 open.
Machine will not shut off.	1.	Input contactor contacts frozen.	1.	Check and replace if necessary.
	2.	Defective Power “I/O”	2.	Replace.
		switch, (S1).
Variable or sluggish welding arc.	1.	Poor work or electrode connec-	1.	Check and clean all connections.
		tion.
	2.	Welding leads too small.	2.	Check table in instruction manual.
	3.	Welding current or voltage too	3.	Check procedures for recom-
		low.		mended settings.
	4.	Defective main SCR bridge.	4.	Check and replace if defective.
Output control not functioning on the	1.	Output Control “Local-Remote”	1.	Place switch in “Local”.
machine.		switch (S2) in wrong position.
	2.	Faulty Output Control switch.	2.	Check and replace if found faulty.
	3.	Faulty Output Control potentiometer.	3.	Check and replace if found faulty.
	4.	Leads or connections open in	4.	Check lead continuity and con-
		control circuit.		nections for an open and repair if
				necessary.
	5.	Faulty Control PC Board.	5.	Replace. See Procedure for
				Replacing PC Boards.

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