Lincoln Electric CITOTIG 315DC Service Manual page 25

CONTROL BOARD, DISPLAY BOARD AND HF BOARD
CONTROL BOARD , DISPLAY
BOARD AND HF BOARD
The control board receives status and feedback
signals from the input board, inverter board,
output board and various sensors.
It receives also commands from the user-
operated controls that are connected to the
control board. These push buttons and
potentiometer's allow the operator to set the
current output of the machine. Other controls
allow for the adjusting all the parameters for the
TIG and Stick welding processes.
The control board processes and compares these
commands with the voltage and current feedback
information it receives from the output current
sensor and the output voltage sensing leads.
Control board also gives error codes, using its
LEDs, to the user, see dedicated section, later on
this service manual.
On the Display board are located the displays,
LEDs, push buttons and output encoders. The
Display Boards functions as the interface between
the user and the machine.
The HF Board generates a set of 40-60Hz pulses
of about 800V-900V. These pulses are applied to
the high frequency transformer that is located in
the negative welding output leg of the machine
and are amplified to about 10KV. This high
frequency/voltage pulse is transferred to the TIG
torch via the high frequency transformer. This
allows the remote starting of the TIG arc without
the need for the tungsten electrode to touch the
work.
This high frequency pulse is switched off when the
welding arc is established.
The HF command signals are received from the
microprocessor on the Control Board and stays
on, if the welding arc is not established for about 3
seconds maximum. The HF Board is supplied
from the input board with 24Vdc and 15Vdc. HF is
not working in Stick and Lift TIG modes.
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