Lincoln Electric SVM100-A service manual Troubleshooting & Repair

Models: SVM100-A

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F-39

TROUBLESHOOTING & REPAIR

 

ABNORMAL OPEN CIRCUIT VOLTAGE - AC STICK MODE

ONE OUTPUT SCR NOT FUNCTIONING

CAUTION

HIGH VOLTAGE / HIGH FREQUENCY can damage test equipment.

Perform all voltage and waveform checks with high frequency circuit OFF.

_____________________________________________________________________

CH1

0 volts

50 volts

2ms

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This is NOT the typical AC output voltage waveform. One output SCR is not function- ing. Note the “gap” in the waveform. One SCR gate was disconnected to simulate an open or non-functioning output SCR. Each vertical division represents 50 volts and each horizontal division represents 2 mil- liseconds in time.

Note: Scope probes connected at machine

output studs: (+) probe to electrode, (–) probe to work.

SCOPE SETTINGS

Volts/Div

50 V/Div.

Horizontal Sweep

2 ms/Div.

Coupling

DC

Trigger

Internal

 

 

SQUARE WAVE TIG 255

Page 80
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Lincoln Electric SVM100-A service manual Troubleshooting & Repair