Lincoln Electric RANGER 250 SVM150-A Service Manual page 91

F-41
Check IGBT for "Shorts"
8. Using the analog ohmmeter, connect the
positive meter probe to the heat sink and the
negative meter probe to the positive capaci-
tor terminal on the power module chopper
PC board. See Figure F.18. The resistance
reading should be high (over 20,000 ohms).
TROUBLESHOOTING & REPAIR
POWER MODULE TEST (continued)
FIGURE F.18 – IGBT TEST
RANGER 250
HEAT SINK
POSITIVE (+)
CAPACITOR
TERMINAL
CONNECTIONS
9. Reverse the meter probe leads. The resis-
tance should be very high (over 20,000
ohms). It the resistance is low in either Step
8 or 9, the IGBT may be shorted or leaky.
F-41