Lincoln Electric Fleet 650 Service Manual page 46

LINCOLN ELECTRIC
14. Label and disconnect leads 23A, 25A, 23 and 25 at the quick-connect terminals. See Wiring
Diagram.
15. Start the engine and allow it to stabilize.
16. If the voltage drops to 0 VDC after leads 23A, 25A, 23 and 25 have been disconnected and the
modules are not shorted, the weld control board is driving the chopper module.
17. Turn off the engine on the Fleet 650 machine.
18. Reconnect leads 23A, 25A, 23 and 25 and perform the Weld Control Board PWM Gate Signal Test
Procedure.
19. Start the engine and allow it to stabilize.
20. Check for about 58 VDC between chopper module board terminals B2+ to B3- and B5+ to B6 and
between the welder output terminals. See Figure F.15. See Wiring Diagram.
21. If about 58 VDC is present at chopper module board terminals B2+ to B3- and B5+ to B6-, but not at
the weld output terminals, there is a problem between the chopper module boards and one of the
weld output terminals. Check for damaged conductors or faulty connections. Also check the shunt,
the chokes and the connections at the back of the weld output terminals. See Wiring Diagram.
22. If the voltage at terminals B2+ to B3- and B5+ to B6- of the chopper module boards are significantly
higher than 58 VDC, check for an open R4 load resistor. See Wiring Diagram.
23. If the voltage at terminals B2+ to B3- and B5+ to B6- of the chopper module boards are very low or
not present, use a frequency counter to check for the presence of a 20 kHZ PWM signal between
leads 23+ and 25- and 23A+ and 25A-, where they connect to the chopper module board. See
Wiring Diagram.
24. If the 20 kHz signal is present but low or no OVC, the chopper module board(s) is defective. Perform
the Chopper Module Boards Removal And Replacement Procedure.
25. If the 20 kHz signal is not present, perform the Weld Control Board PWM Gate Signal Test
Procedure.
26. If the weld control board is producing a PWM gate signal, check leads 23, 25, 23A and 25A for
damaged conductors and faulty connections between the weld control board and the chopper
module boards.
27. Turn off the engine on the Fleet 650 machine.
28. When testing is complete, connect any previously disconnected leads.
29. When testing is complete, perform the Case Cover Replacement Procedure.
LED
1
2
3
Table F.4 – Chopper module LED tests
COLOR
GREEN
GREEN
GREEN
Fleet™ 650 Service Manual
INDICATION
PWM INPUT PRESENT
15 VDC POWER SUPPLY PRESENT
CHOPPER OUTPUT PRESENT
41