Lincoln Electric R3R-300 Abnormal Output Voltage Waveform, ONE Output SCR not Functioning

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F-38 F-38

TROUBLESHOOTING & REPAIR

ABNORMAL OUTPUT VOLTAGE WAVEFORM

ONE OUTPUT SCR NOT FUNCTIONING

0 volts

50 volts 5 ms

This is NOT the typical DC output voltage waveform. One output SCR is not functioning. Note the “GAP” in the waveform. One SCR gate is dis- connected to simulate an open or non-functioning output SCR. Each vertical division represents 50 volts and each horizontal division repre- sents 5 milliseconds in time. The machine was loaded with a resis- tance grid bank.

Note: Scope probes connected at

machine output terminals: (+) probe to positive terminal, (-) probe to neg- ative terminal. (R3R 500 machine)

SCOPE SETTINGS

Volts/Div	50V/Div.
Horizontal Sweep	5 ms/Div.
Coupling	DC
Trigger	Internal

IDEALARC R3R