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THEORY OF OPERATION
E-4 E-4
SQUARE WAVE TIG 275
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HIGH VOLTAGE / HIGH FREQUENCY
CIRCUIT
The control board passes the 115 VAC voltage to the
primary of the high voltage transformer. The secondary
of the high voltage transformer is coupled to a spark
gap generator and also to the high frequency trans-
former. The high frequency transformer transfers the
high frequency “spark” to the electrode terminal, which
is coupled to the TIG torch.
NOTE: Unshaded areas of Block Logic Diagram are the subject of discussion.
FIGURE E.4 – HIGH VOLTAGE / HIGH FREQUENCY CIRCUIT
INPUT
POWER
SWITCH
MAIN
TRANSFORMER
POLARITY
SWITCH
SCR
BRIDGE
X1
X2
AC
AC
DC+
DC-
CONTROL
BOARD
18VAC
18VAC
115VAC
FAN
REMOTE
RECEPTACLE
H1
H2
H3
SHUNT
115VAC
HIGH VOLTAGE
TRANSFORMER
CIRCUIT
BY-PASS
BOARD
HI-FREQUENCY
TRANSFORMER
C
H
O
K
E
WORK
ELECTRODE
THERMAL
LIGHT
GAS
VALVE
OUTPUT
CONTROL
MODE
SWITCH
F
E
E
D
B
A
C
K
H4
"A"
RECONNECT
PANEL
23VAC
DOWNSLOPE
CONTROL
POSTFLOW
CONTROL
BALANCE
CONTROL
THERMOSTATS
115VAC
RECEPTACLE