Lincoln Electric SVM138-A service manual Figure E.3 Trigger and Shutdown Circuit

Section TOC

Master TOC

E-3 E-3

THEORY OF OPERATION

FIGURE E.3 – TRIGGER AND SHUTDOWN CIRCUIT

VOLTAGE CONTROL

WORK VOLTAGE SENSING

Return to

Return to Section TOC

Return to

Return to Master TOC

				GEAR		ELECTRODE VOLTAGE SENSING
				BOX
				WIRE
				FEED
				MOTOR		HALL EFFECT
						DEVICE
POWER SOURCE OUTPUT TRIGGER			(#2 )
						WIRE SPEED CONTROL
						+ 15VDC
		TRIGGER		T2
	TRIGGER	BOARD				GAS
CIRCUIT
	CONNECTOR					SOLENOID
BREAKER			24VAC
INPUT						TRIGGER SIGNAL
				F
				U
CONNECTOR				S
				E
R1				P	B	+ 15VDC
				O	O
				W	A	S
				E	R
						H
				R	D	U
						T
TO						D
						O
CONTROL						W
BOARD						N

T1

TO

VOLTAGE

BOARD

METER 10VAC 28VAC

BOARD

VOLTS

SPEED

SWITCH

POLARITY

SWITCH

WIRE

SPEED

CONTROL

C

OB

NO

TA

RR

D

O

L

RV E O F

E L R T E A N G C E

E

VOLTAGE

CONTROL

VOLTAGE

BOARD

to Section TOC

to Master TOC

TRIGGER SIGNAL

GROUND

LEAD

PROTECTOR

TRIGGER AND SHUTDOWN

CIRCUIT

Return

Return

When the gun trigger switch is activated (closed), the trigger board completes the trigger signal path. This energizes the CR1 relay located on the power board. The CR1 relay activates the wire drive motor and the #2 and #4 circuit, which then activates the Lincoln welding power source. The CR1 relay is also used to energize the gas solenoid.

The normally closed relay located on the voltage board is in series with the trigger signal. If an out-of- voltage-range signal or a ground fault condition should occur, the CR501 (on voltage board) relay con- tacts would "open," and the trigger signal path would be interrupted. This would cause the wire feeder to "shut down" until the gun trigger is released or the ground fault protector is reset.

Return to Section TOC

Return to Master TOC

NOTE: Unshaded areas of Block Logic Diagram are the subject of discussion.

LN-9 GMA Wire Feeder