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The arc burns back to the tip.
The gas continues to flow for a
long time after the weld.
1. If timer kit is installed, reduce
the amount of burnback time.
2. If the timer kit is installed,
reduce the amount of post flow
time.
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TROUBLESHOOTING & REPAIR
F-5 F-5
LF-72/74
Observe Safety Guidelines detailed in the beginning of this manual.
PROBLEMS
(SYMPTOMS)
POSSIBLE AREAS OF
MISADJUSTMENT(S)
RECOMMENDED
COURSE OF ACTION
FUNCTION PROBLEMS (Continued)
No shielding gas. 1. No gas supply, or gas supply
interrupted.
2. Solenoid not functioning.
1. Verify cylinder is not empty and
is turned on.
Check the hose for cuts or kinks.
Make sure it is not crushed.
Verify the hose is connected to the
gun bushing or welding gun.
2. Perform the
GAS SOLENOID
TEST.
Variable or hunting arc. 1. Bad contact tip
2. Possible loose connection in
current carrying cables.
3. Set up not correct.
4. Problem with shielding gas.
1. Check for proper size contact
tip. Make sure tip is not worn,
and is free of spatter.
2. Clean and tighten all electrode
and work connections. Verify
the gun bushing is tightly
mounted to the wire drive.
Verify the gun is tightly mounted
to the gun bushing.
3. Verify the proper polarity is
being used for the weld proce-
dure. Make sure the proper
electrode stick-out is being
maintained.
4. Check the gas flow rate and
mixture.
5. Control board may be faulty.
When the trigger is pulled, the
drive rolls spin but no arc voltage
1. Possible bad gun or faulty con-
nections in the heavy current
carrying leads.
2. Possible faulty control cable.
3. Possible defective power
source.
1. Check all electrode and work
connections. Verify the the gun
bushing is tight to the wire
drive. Verify gun is tightly
mounted to the bushing.
2. Check the control cable and
connectors for continuity, cuts,
or broken pins.
3. Verify the power source is oper-
ating properly.
LF-72/74 SINGLE/DUAL
CAUTION
If for any reason you do not understand the test procedures or are unable to perform the test/repairs safely, con-
tact the Lincoln Electric Service Department at 1-888-935-3877 for electrical troubleshooting assistance before
you proceed.