Lincoln Electric 11694 Service Manual page 60

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POWER WAVE S350
B51
B39
B38
PROCEDURE
1. Remove the input power to the Power Wave S350 machine.
2. Perform the Case Cover Removal and DC Link Capacitor
Discharge Procedure.
3. Locate test points B51, B38 and B39. See Figure F.22. See
Wiring Diagram.
4. Disconnect lead #207 from the 200 ohm 100 watt output resistor.
See Wiring Diagram.
5. Using the ohmmeter, check the resistances from B51 to B38/B39.
Polarity of the ohmmeter is important. See Wiring Diagram.
6. With the positive meter probe on B51 and the negative meter
probe on B38/B39 the resistance reading should be very high. See
Wiring Diagram.
7. With the positive meter probe on B38/B39 and the negative probe
on B51 the resistance reading should be very low. Thus a forward
diode drop. See Wiring Diagram.
8. If the meter readings indicate a very low resistance in both
directions, the output rectifier may be shorted.
9. If the meter readings indicate a very high resistance in both
directions, the output rectifier may be open.
10. If the output rectifier is faulty, the entire switch board must be
replaced.
OUTPUT RECTIFIER TEST
Figure F.22 – Output rectifier test points
(continued)
11. If faulty, perform the Switch Board Removal And
Replacement Procedure.
12. Connect the previously removed lead #207 to the 200 ohm 100
watt output resistor. See Wiring Diagram.
13. Perform the Case Cover Replacement Procedure.
TROUBLESHOOTING AND REPAIR
54