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F-34

TROUBLESHOOTING & REPAIR

F-34

 

 

ABNORMAL OUTPUT VOLTAGE WAVEFORM - MACHINE LOADED

ONE OUTPUT SCR NOT FUNCTIONING

MACHINE LOADED TO 220 AMPS AT 22 VDC

SCOPE SETTINGS

This is NOT a typical DC output voltage

 

 

waveform. One output SCR is not function-

Volts/Div

.20 V/Div.

ing. Note the increased ripple content. One

 

 

SCR gate was disconnected to simulate an

Horizontal Sweep

.5 ms/Div.

open or non-functioning output SCR. Each

 

 

vertical division represents 20 volts and

Coupling

. . . . .DC.

each horizontal division represents 5 mil-

 

 

liseconds in time. The machine was loaded

Trigger

. .Internal.

with a resistance grid bank.

 

 

Note: Scope probes connected at machine

 

 

output terminals: (+) probe to electrode, (-)

 

 

probe to work.

 

 

 

 

 

IDEALARC SP-250

Page 81
Image 81
Lincoln Electric SP-250 service manual Machine Loaded to 220 Amps AT 22 VDC Scope Settings