Lincoln Electric IDEALARC SP-255 Service Manual page 84

F-31
ABNORMAL OUTPUT VOLTAGE WAVEFORM - MACHINE LOADED
This is NOT a typical DC output voltage
waveform. One output SCR is not function-
ing. Note the increased ripple content. One
SCR gate was disconnected to simulate an
open or non-functioning output SCR. Each
vertical division represents 20 volts and each
horizontal division represents 5 milliseconds
in time. The machine was loaded with a re-
sistance grid bank.
Note: Scope probes connected at machine
output terminals: (+) probe to electrode, (-)
probe to work.
TROUBLESHOOTING & REPAIR
ONE OUTPUT SCR NOT FUNCTIONING
MACHINE LOADED TO 220 AMPS AT 22 VDC
IDEALARC
SCOPE SETTINGS
Volts/Div . . . . . . . . . . . . . . . . . .20 V/Div.
Horizontal Sweep . . . . . . . . . .5 ms/Div.
Coupling . . . . . . . . . . . . . . . . . . . . . .DC.
Trigger . . . . . . . . . . . . . . . . . . . .Internal.
® SP-255
F-31