Lincoln Electric 11519 Service Manual page 76

F-30
AND TACHOMETER FEEDBACK TEST (continued)
TEST FOR FEEDBACK VOLTAGE
TO CONTROL BOARD
1. Disconnect the main AC input power to the
machine.
2. Locate plug J1 on the control PC board.
3. Locate the following leads on plug J1 (see
Figure F.9):
LEAD
555
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.
c. Turn the machine ON and pull the gun trig-
ger to conduct the voltage test.
FROM TO
LEAD LEAD
555 206B
(6J1) (1J1)
TROUBLESHOOTING AND REPAIR
WIRE DRIVE MOTOR
PLUG
LOCATION
6J1
1J1
EXPECTED
VOLTAGE
1.5 to 3.5 VDC
Power MIG® 255XT
6. If the 1.5 to 3.5 VDC is present, the tachometer
circuit is sending the correct feedback signal to
the Control PC Board.
7. If the 1.5 to 3.5 VDC is not present or not cor-
rect, the Control PC Board is not receiving the
proper feedback voltage from the tachometer
circuit. Check the leads from the tachometer cir-
cuit to the control PC board for loose or broken
connections.
8. If the leads are okay, the tachometer circuit may
be faulty, replace the tachometer circuit.
9. Replace the tool tray.
F-30