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D-2 D-2
LF-72/74
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MAINTENANCE
MAINTENANCE
Safety Precautions
ELECTRIC SHOCK can kill.
• Do not touch electrically live parts
such as output terminals or inter-
nal wiring.
• When inching with gun trigger, electrode and
drive mechanism are “hot” to work and ground
and could remain energized several seconds
after the gun trigger is released.
• Turn OFF input power at welding power source
before installation or changing drive roll and/or
guide tubes.
• Welding power source must be connected to sys-
tem ground per the National Electrical Code or
any applicable local codes.
• Only qualified personnel should perform mainte-
nance work.
------------------------------------------------------------------------
WARNING
Observe all additional Safety Guidelines detailed
throughout this manual.
ROUTINE MAINTENANCE
• Clean and tighten all weld terminals.
• Inspect all weld cables, control cables, gun cables
and shielding gas hoses. Repair or replace as nec-
essary.
PERIODIC MAINTENANCE
• Clean drive roll grooves.
• Blow out or vacuum the inside of the feeder.
CALIBRATION SPECIFICATION
ELECTRIC SHOCK can kill.
• Do not touch electrically live parts.
• When inching with the gun trigger,
electrode, wire drive motor and
drive mechanism are "hot" to work
and ground and could remain
energized several seconds after
the gun trigger is released.
• Welding power source must be
connected to system ground per
the National Electrical Code or any
applicable local codes.
• Only qualified personnel should perform mainte-
nance work.
------------------------------------------------------------------------
Calibration of the LF-72 may be required when the p.c.
board, potentiometer or motor is replaced or serviced.
Calibration matches the scale on the name plate to the
actual wire feed speed.
To verify if calibration is necessary:
1. Turn off power to the LF-72.
2. Assemble .045 drive rolls, inner guide and the
outer guide into the drive. Remove the gun from
the wire feeder if assembled.
3. Load .045 wire into the drive. Cut the wire flush
with the end of the gun bushing.
4. Set the WFS knob to 300 ipm.
5. Using the COLD FEED switch, feed wire for 10
seconds.
6. Cut the wire flush with the end of the gun bushing.
Measure the length of the wire. If the wire mea-
sures 50 ± 2.5 inches then calibration is not
required.
Tools required:
5/16" nut driver
3/4" open end wrench
WFS meter or RPM meter
Shorting plug. The shorting plug shorts pins 1
& 5 of connector J2 on the p.c. board. J2 is a
6 pin molex connector.
To calibrate the LF-72:
1. Turn off power to the LF-72.
2. Disconnect the electrode lead from the feedplate
and from the welding power source.
3. Remove the 5 screws securing the wraparound.
(The door is not shown for clarity. “
See Figure
D.1”)
WARNING