PRECISION TIG 185
THEORY OF OPERATION
E-3 E-3
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OUTPUT RECTIFICATION AND
FEEDBACK CONTROL
The AC output from the main transformer secondary is
rectified and controlled through the SCR bridge.
Output current is sensed at the shunt as a low voltage
signal and fed back to the control board. The control
board compares the commands of the mode switch,
output control, AC balance control, pulse control, post-
flow control, or remote control with the feedback infor-
mation. The appropriate SCR gate firing signals are
created by the control board and sent to the SCR
bridge. The control board controls the firing of the
SCRs, which control the output of the machine. See
SCR Operation. The control board monitors the ther-
mostats, and also controls the gas solenoid valve, ther-
mal light, auto balance LED, pulse frequency LED, TIG
LED, stick LED, and the digital display.
FIGURE E.3 Control Board and Output Feedback Control.
