Lincoln Electric PERKINS SA-250 - Manual (Page 19)

– 18 –
TROUBLE
A. Machine fails to hold the “heat”
consistently.
B. Welder starts but fails to gener-
ate current.
C. Welding arc is loud and spat-
ters excessively.
CAUSE
1. Rough or dirty commutator.
2. Brushes may be worn down to
limit.
3. Field circuit may have variable
resistance connection or inter-
mittent open circuit due to loose
connection or broken wire.
4. Electrode lead or work lead con-
nection may be poor.
5. Wrong grade of brushes may
have been installed on genera-
tor.
6. Field rheostat may be making
poor contact and overheating.
1. Generator or exciter brushes
may be loose or missing.
2. Exciter may not be operating.
3. Field circuit of generator or
exciter may be open.
4. Exciter may have lost excitation.
5. Series field and armature circuit
may be open-circuited.
1. Current setting may be too high.
2. Polarity may be wrong.
WHAT TO DO
1. Commutator should be turned
or cleaned.
2. Replace brushes.
3. Check field current with ammeter
to discover varying current. This
applies to both the main genera-
tor & the exciter.
4. Tighten all connections.
5. Use Lincoln brushes.
6. Inspect & clean the rheostat.
1. Be sure that all brushes bear on
the commutator and have proper
spring tension.
2. Check exciter output voltage
with voltmeter or lamp.
3. Check for open circuits in rheo-
stat, field leads and field coils.
Check rectifier bridge.
4. Flash fields. (1)
5. Check circuit with ringer or volt-
meter.
1. Check setting and current output
with ammeter.
2. Check polarity. Try reversing
polarity or try an electrode of the
opposite polarity.
TROUBLESHOOTING
(1) See FLASHING THE FIELDS on following page.