Troubleshooting (Cont) - Lincoln Electric SHIELD-ARC 400AS-50 Operating Manual

TROUBLE
Machine starts, but has
the following faults:
continued:
Welding is loud and
spatters excessively
Maximum welding
output all the time
Battery not charging
Battery over-charging
Auxiliary power fails
under load
Welding current too
great or too small
ompared to indication
on dial.
Welding output ok., but
no auxiliary output.
IMA 554C

TROUBLESHOOTING (Cont)

CAUSE
Short circuit in armature (7A).
(2 segments burnt in 4 locations 90° apart).
Field rheostat may be making poor contact and
overheating (9).
Field circuit may have variable resistance connections
or intermittent open circuit, due to loose connections or
broken wires (17), (8), (9) or (9A).
Current control brushholder support stud and mating
contact surfaces may be dirty or pitted and burned
(5A).
Current control brushholder contact springs may be
worn out or missing. Contact surface may be dirty,
rough or pitted (5A).
Current-adjusting mechanism may not be operating
properly (5A).
Engine speed low.
Wrong grade of brushes may have been installed on
generator (7).
Series field (5) and armature circuit may be open
circuited (7A).
Current setting may be too high.
Polarity may be wrong.
Open in series coil (5).
Faulty battery charge alternator (22)
Faulty meter (14)
Battery may be fully charged.
Faulty battery charge alternator (22).
Capacitors faulty (13).
Current control shaft and handle (5) may have turned
slightly in the insulated bushing of the current control
brushholder, caused by turning handle too hard against
one of the stops.
Alternator low causing low output compared
to dial indication.
Current control set to minimum and welder output so
great that the engine stalls when arc is struck.
Engine running at incorrect speed.
Aux power circuit breaker tripped.
Broken wires.
Open circuit in auxiliary power (18) windings
Shield-Arc 400AS-50
WHAT TO DO
Locate fault using growler and repair or
replace
Inspect rheostat. Clean out and if necessary
increase finger tension on contact arm
by bending arm.
Check field current with ammeter to
discover varying current. This applies to
both the main generator and alternator.
If brushholder internal contact surface is
pitted and burned, replace the
brushholder and support stud. If the
contact tact surface is dirty, clean off the
brushholder stud and internal contact
surface. Apply mixture of three parts
silicone grease and one part zinc
powder (by weight) to stud.
Inspect. Replace needed parts. Clean
internal contact surface of control device.
Do not Iubricate. Smooth up roughened
surface.
Check for loose or missing set screw in
control handles.
Check nameplate for desired speed and
reset. (Refer engine instruction manual.)
Fit correct Lincoln brushes
Check circuit with voltmeter
Check setting and current output with
ammeter
Check polarity. Try reversing polarity or
try an electrode of the opposite polarity
Repair or replace
Repair or replace
Repair or replace meter
Repair or replace
Replace capacitors
With current control against the
minimum stop, set the pointer to within
3mm of last scale division.
Check for faulty rotor circuits
Check to see that the series field is
properly connected & not shorted.
Set welder controls for maximum output
and weld. Then, while welding, check
engine R.P.M. The engine should be
running at full load speed. If indicator
shows a significant difference, consult
your engine instruction manual.
Reset
Repair or replace
Repair or replace stator
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