Lincoln Electric NA-3S, Service Manual, Page: 87 / 110

TROUBLESHOOTING AND REPAIR
F-22 F-22
NA-3 AND NA-4
WIRE FEED DRIVE MOTOR TEST
(continued)
TEST POINTS RESISTANCE DC VOLTAGE
Lead #539 to lead #541 4 to 5 ohms 0 to 90 VDC
armature
Lead #626 to lead #627 750 to 850 ohms 90 to 120 VDC
field winding
All leads 500,000 ohms min. Not Applicable
to
motor shell
TABLE F.1 – DRIVE MOTOR POINTS.
TEST PROCEDURE
1. Remove the wire feed motor
connector from the NA-3/NA-4 control
box.
2. Using the ohmmeter, measure the
resistances per Table F.1. Also see
Figure F.5.
3. If the motor resistance test is good,
proceed to the Motor Applied
Voltage Test.
FIGURE F.5 – WIRE FEED DRIVE
MOTOR CONNECTOR PINS.
MOTOR APPLIED
VOLTAGE TEST
1. Carefully connect the isolated
120 VDC supply (SUPPLY TURNED
OFF) to pins C and D on the motor
connector.
2. Carefully connect the variable 0 to
90 VDC supply (SUPPLY TURNED
OFF) to pins A and B on the motor
connector. (See Table F.1.)
3. Apply field voltage first (pins C and
D) to the motor. Then, slowly apply
the armature voltage to pins A and B.
(See Table F.1).
4. The motor should run, and the speed
should vary with changes to the
armature voltage.
5. If the motor does NOT run and
change speed correctly, the motor or
gear box may be faulty.
6. To stop the motor, REMOVE THE
ARMATURE VOLTAGE FIRST (pins
A and B).
E
D C
B
A
MOTOR
CONNECTOR
PIN
#539
#541
#627
#626