Welder Troubleshooting - Lincoln Electric CLASSIC 300 D Operator's Manual

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TROUBLE
1. Machine fails to hold
the output (heat) consistently.
2. Welder starts but fails
to generate current.
(1) FLASHING THE FIELDS:
1. Stop the engine welder and remove the cover from the exciter.
2. Turn the "Fine Current Adjustment" (rheostat) to "100" on the dial.
3. Using a 12 volt automotive battery, connect it's negative terminal to the negative brushholder. The
negative brushholder is the one nearest to the rotor lamination. See the wiring diagram. With the
engine NOT running, touch the positive battery terminal to the positive brushholder. Remove the
battery from the circuit.
4. Replace the exciter cover. Start the welder and the generator voltage should build up.
3. Welding arc is loud and
spatters excessively
4. Welding current too great or too
small compared to indication on
the dial.
5. Arc continuously pops out.
TROUBLESHOOTING

WELDER TROUBLESHOOTING

CAUSES
a. Rough or dirty commutator.
b. Brushes may be worn down to
limit.
c. Field circuit may have variable
resistance connection or
intermittent open circuit due to
loose connection or broken wire.
d. Electrode lead or work lead
connection may be poor.
e. Wrong grade of brushes may
have been installed on generator.
f. Field rheostat may be making
poor contact and overheating.
a. Generator or exciter brushes
may be loose or missing.
b. Exciter may not be operating.
c. Field circuit of generator or
exciter may be open.
d. Exciter may have lost excitation.
e. Series field and armature circuit
may be open-circuited.
a. Current setting may be too high.
b. Polarity may be wrong.
a. Exciter output low causing low output
compared to dial indication.
b. Operating speed too low or too high.
a. "Current Range Selector" switch may be
set at an intermediate position.
CLASSIC 300D
WHAT TO DO
a. Commutator should be turned or
cleaned.
b. Replace brushes.
c. Check field current with ammeter to
discover varying current. This
applies to both the main generator
and exciter.
d. Tighten all connections.
e. Use Lincoln brushes.
f. Inspect and clean the rheostat.
a. Be sure that all brushes bear on the
commutator and have proper spring
tension.
b. Check exciter output voltage with
voltmeter or lamp.
c. Check for open circuits in rheostat,
field leads, and field coils. Check
rectifier bridge.
d. Flash fields. (1) Check flashing
diode at 5 o'clock brushholder in
generator.
e. Check circuit with ringer or voltmeter.
a. Check setting and current output with ammeter.
b. Check polarity. Try reversing polarity or try an
electrode of the opposite polarity.
a. Check exciter field circuit.
b. Adjust speed with screw stops at throttle linkage.
(High idle - 1800 RPM, Low idle - 1375 RPM)
a. Set the switch at the center of the current range
desired.
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