Lincoln Electric SVM136-A service manual Abnormal Output Voltage Waveform Machine Loaded

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F-31 F-31

TROUBLESHOOTING & REPAIR

ABNORMAL OUTPUT VOLTAGE WAVEFORM - MACHINE LOADED

ONE OUTPUT SCR NOT FUNCTIONING

CH1

0 volts

20 volts 5 ms

This is NOT the typical DC output voltage waveform. One output SCR is not functioning. Note the “ripple” in the waveform. One SCR gate is disconnected to simulate an open or non-functioning output SCR. Each vertical division represents 20 volts and each horizontal division repre- sents 5 milliseconds in time. The machine was loaded with a resis- tance grid bank. The CV-400 meters read 400 amps at 36 VDC.

Note: Scope probes connected at

machine output terminals: (+) probe to positive terminal, (-) probe to neg- ative terminal.

SCOPE SETTINGS

Volts/Div	20V/Div.
Horizontal Sweep	5 ms/Div.
Coupling	DC
Trigger	Internal

IDEALARC CV-400