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D-4
MAINTENANCE
LN-7 & LN-7 GMA
D-4
LN-7 SEQUENCE OF OPERATION (Optional Timer Kit not Installed)
Turn on Power Source
Closes 524-525
Closes 31-7A circuit
115V AC input power
is applied to SCR
control circuit and
Motor Armature
(539-541 circuit) is
energized
Energizes 1 CR
Press Gun Trigger
Closes 2-4 Circuit
Energizes welder
pilot relay
and/or
Energizes welder
contactor
Electrode now
“hot” to ground
Energizes aux. equipment
(gas solenoid) connected
to 7-32A with 115 VAC
Wire feed motor starts
at low speed and increases
speed to welding speed
Arc Starts
Welding
Release Gun Trigger
Opens 524-525
De-Energizes 1 CR
Opens 31-7A circuit
Disconnects motor
armature from SCR control.
1CR normally closed contact
closes shorting armature
thru dynamic braking
resistor.
Opens 2-4 Circuit
De-energizes welder
pilot relay
and/or
De-energizes welder
contactor
Electrode is
“cold” to work
Auxiliary equipment
de-energized
Wire feed motor stops
Unit ready for next weld