Lincoln Electric SAE-300 HE, Service Manual, Page: 43 / 84

LINCOLN ELECTRIC SAE-300® HE Service Manual
38
WELD CIRCUIT GROUND AND SHORT CIRCUIT TEST PROCEDURE
Service and repair should be performed by only Lincoln Electric factory trained personnel. Unauthorized
repairs performed on this equipment may result in danger to the technician or machine operator and will
invalidate your factory warranty. For your safety and to avoid electrical shock, please observe all safety
notes and precautions detailed throughout this manual. 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.
TEST DESCRIPTION
This procedure checks for grounded components in the Weld Circuit. It also checks for a short circuit
condition between the positive and negative components of the Weld Circuit.
This test cannot detect a short circuit within the Armature or a turn to turn short circuit within a Coil or Coil
Set.
IMPORTANT: The machine must be clean and completely dry before this test is done.
MATERIALS NEEDED
Volt/Ohmmeter
Wiring Diagram
TEST PROCEDURE
1. Turn off the engine on the SAE-300 HE machine.
2. Open either, or both of the side covers and secure them with the hooks provided.
3. Remove the sheet metal cover protecting the welder generator brushes.
Weld circuit ground test:
4. Rotate the coarse current control to the minimum output position.
5. Using a volt/ohmmeter, measure the resistance between either of the two weld output terminals
and a clean chassis ground connection. See Wiring Diagram.
6. The resistance measurement should be very high 500,000 (500k) Ohms minimum.
If the resistance is lower than 500k Ohms:
7. Move the output control away from the minimum position and recheck the resistance. If the
resistance is now 500k Ohms or greater; check for a damaged or missing insulator bushing at the
output control unit.
8. If the resistance is still less than 500k Ohms, remove the welding generator brushes, or pull them
away from the commutator and isolate them so they cannot come in contact with anything except
the brush holder where they are attached.
9. Label and disconnect plug #P10 from the receptacle #J5 and be certain none of the conductors can
come in contact with chassis ground or any other wiring.
10. Using a volt/ohmmeter, measure the resistance between chassis ground and each output terminal
and between chassis ground and the commutator.
If the commutator has low resistance to chassis ground, the armature is defective.