Lincoln Electric Classic 300 MP Service Manual page 21

LINCOLN ELECTRIC
Observe Safety Guidelines
detailed in the beginning of this manual.
PROBLEMS
(SYMPTOMS)
The engine starts and runs at
correct speed, but there is no
or very low, welder output
voltage. The AC auxiliary
output voltage is normal.
If for any reason you do not understand the test procedures or are unable to perform the test/repairs safely, contact the
Lincoln Electric Service Department for electrical troubleshooting assistance before you proceed. Call 1-888-935-3877.
POSSIBLE AREAS OF
MISADJUSTMENT(S)
OUTPUT PROBLEMS
1. Check for loose or missing
brushes in the welding
generator.
2. Check the welding cables for
loose or faulty connection.
Classic® 300 MP Service Manual
TROUBLESHOOTING GUIDE
RECOMMENDED
COURSE OF ACTION
1. Perform the Control Board
Test Procedure.
2. Perform the Shunt Field Coil
Resistance And Ground Test
Procedure.
3. Perform the Weld Circuit
Ground And Short Circuit Test
Procedure.
4. Check the continuity of the
interpole coils. They should
show continuity from the
positive brush holders to the
positive output terminal and
should NOT be grounded to the
generator frame.
5. Perform the Shunt Field
Circuit Voltage Test Procedure.
6. Perform the Rocker
Adjustment Procedure.
7. Check the continuity of the
series coils. They should show
continuity from the negative
brush holders, through the
current range selector switch,
to the negative output terminal
and should NOT be grounded.
8. Perform the Selector Switch
Test Procedure.
9. The main armature may be
faulty. Check for grounds
and/or shorts.
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