THEORY OF OPERATION

E-4 E-4

PRECISION TIG® 225
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HIGHVOLTAGE/ HIGH FREQUENCYCIRCUIT

The control board passes the 115VAC 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.

FIGURE E.2 - High Voltage/HighFrequency Circuit.

NOTE: Unshaded areas of Block Logic

Diagram are the subject of discussion

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
HIGHVOLTAGE
TRANSFORMER
CIRCUIT
BY-PASS
BOARD
HI-FREQUENCY
TRANSFORMER
C
H
O
K
E
WORK
ELECTRODE
THERMAL GAS THERMO-
STATS
OUTPUT
MODE
SWITCH
POWER
"ON"
DIGITAL
DISPLAY
F
E
E
D
B
A
C
K
BYPASS
ASBLY

115 VAC

Receptacle

CircuitBreaker

Protected