Lincoln Electric POWER MIG SVM170-A Service Manual page 69

F-29
WIRE DRIVE MOTOR AND TACHOMETER FEEDBACK TEST (continued)
6. Make the following voltage tests:
a. Turn the machine OFF between
b. Carefully insert the meter probes
c. Turn the machine ON and pull the
FROM
LEAD
B
(4J1)
7. If the voltage to the wire drive motor
armature is zero, check the wires
between plug J1 and the wire drive
motor. Also check the electrical connec-
tor J12 for proper connection and con-
tact.
8. If all wires and connectors are good and
the voltage to the drive motor armature
is zero, the control PC board may be
faulty, replace the control PC board.
9. If the motor is running at high speed
and the armature voltage is high and
uncontrollable,
tachometer test.
TEST FOR SUPPLY VOLTAGE
TO TACHOMETER
1. Disconnect the main AC input power to
the machine.
TROUBLESHOOTING AND REPAIR
each test.
into the back of each Molex plug
pin cavity to perform the test.
gun trigger to conduct the voltage
test.
TO EXPECTED
LEAD VOLTAGE
W 3-20 VDC
(2J1) (varies depend-
ing on wire feed
speed)
proceed with
POWER MIG 255C
2. Locate plug J1 on the control PC board.
See Figure F.9.
3. Locate the following leads on Plug J1:
LEAD
515B
206B
4. Connect main input power to the
machine.
5. Make the following voltage tests:
a. Turn the machine OFF between
each test.
b. Carefully insert the meter probes
into the back of each Molex plug
pin cavity.
FROM
LEAD
515B
(5J1)
6. If the 15 VDC is present, check the
leads to the tachometer circuit.
7. If the leads are okay and 15 VDC is
present, the correct voltage is being
received from the control PC board,
the continue with the Supply Voltage to
Tachometer Test.
8. If the 15 VDC is not present and the
leads are okay, the control PC board
may be faulty, replace the control PC
board.
F-29
PLUG
LOCATION
5J1
1J1
TO EXPECTED
LEAD VOLTAGE
206B 15 VDC
(1J1)