Theory Of Operation - Lincoln Electric PRECISION TIG SVM186-A Service Manual

E-4
TRANSFORMER
INPUT
POWER
SWITCH
BYPASS
ASBLY
H1
H2
H3
115 VAC
FAN
Receptacle
Circuit Breaker
Protected
REMOTE
RECEPTACLE
HIGH VOLTAGE / HIGH FREQUENCY
CIRCUIT
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.

THEORY OF OPERATION

FIGURE E.2 - High Voltage/High Frequency Circuit.
POLARITY
SWITCH
MAIN
AC DC+
X1
SCR
BRIDGE
X2
DC-
AC
18VAC
18VAC
115VAC
THERMAL
NOTE: Unshaded areas of Block Logic
Diagram are the subject of discussion
PRECISION TIG® 225
BY-PASS
BOARD
C
H
O
K
E
HIGH VOLTAGE
SHUNT
TRANSFORMER
CIRCUIT
F
E
E
D
B
A
C
K
115VAC
CONTROL
BOARD
SWITCH
THERMO-
GAS OUTPUT
STATS
WORK
ELECTRODE
HI-FREQUENCY
TRANSFORMER
POWER
"ON"
DIGITAL
DISPLAY
MODE
E-4