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LH20/1:4
TIG mode operation
Tig mode is selected with switch S1 middle position. While TIG mode is active the
ANTISTICK function is enabled, and HOT START and ARC FORCE functions are
disabled.
In TIG mode transistor V35 is open. Transistors V36, V37, V38 are also open untill
trigger on welding torch is pressed. After trigger is pressed rectifier bridge VB2 is
supplied from transformer T2 winding via voltage divider R60, R61. Consequently
transoptor VC1 is turned on (LED V13 is lit) what makes high level appear on D2b
gate input, as well as transoptor VC2 is turned on through resistor R71. Transoptor
VC2 turns on transistors V36, V37, V38 that control contact arc striking circuit, that
consists of auxiliary bridge and resistor R1 (see the machine diagram).
Edition 071024
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