Lincoln Electric COMMANDER SVM145-B Service Manual page 113

F-57
CHECK IGBT FOR "SHORTS"
5. Using the analog ohmmeter, connect the pos-
itive meter probe to the heat sink and the neg-
ative meter probe to the positive capacitor ter-
minal on the chopper PC board. See Figure
F.26. The resistance reading should be very
high (over 20,000 ohms).
TROUBLESHOOTING & REPAIR
POWER MODULE TEST (continued)
FIGURE F.26 – IGBT TEST
HEAT SINK
COMMANDER 300
POWER MODULE
(CHOPPER PC BOARD)
REMOVE LEADS
6. Reverse the meter probe leads. The resis-
tance should be very high (over 20,000
ohms). It the resistance is low in either Step
5 or 6, the IGBT may be shorted or leaky.
7. Repeat Steps 4 and 5 for the other module.
F-57