Lincoln Electric IM10063 TCV400 - Manual (Page 24)

E-5 TROUBLESHOOTING E-5
TCV400
PROCEDURE FOR REPLACING PC
BOARDS
When a PC board is suspected to be defective, the
following procedure must be followed:
1. Visually inspect the PC board. If the board has
fuses, check to see if any are blown. Are any of
the components damaged? Is a conductor on the
back side of the board damaged? If electrical dam-
age is visible on the PC board, inspect the
machine wiring for grounds or shorts to avoid
damaging a new PC board. Install a new PC board
only after a visual inspection of the PC board and
machine wiring is satisfactory.
2. If the problem is remedied by a new PC board,
install the old PC board and see if the problem still
exists. If the problem does not return with the old
board:
• Check the PC board harness plug and PC board
plug for contamination, corrosion or oversize.
• Check leads in the harness for loose connec-
tions.
FAULT PROTECTION OPERATION
The overload protection circuit, in the Control Board,
will limit the welding current (heat) to approximately
550 amps if a short or overload is applied to the
machine.
CHECKING SNUBBER PC BOARD
In case of an SCR malfunction or failure, the Snubber
PC Board should be checked. Turn the machine off
and remove the sides of the machine. Board is mount-
ed on back of the Front Panel.
1. Visually inspect the Board for overheated compo-
nents or damaged components.
POWER “ I/O “ SWITCH CHECK
1. Turn off the machine input power (“0” position). S1
has 115 volts across it when the input power is
connected.
2. Isolate the switch to be tested by removing all con-
necting leads.
3. Check to make sure the switch is making open
and closed connections with a V.O.M. meter. Put
ohmmeter on X1 scale. The meter should read
zero resistance with switch “I” and infinite with
switch “0”.
4. Put the ohmmeter on X1K scale and measure the
resistance between the terminal and the case of
the machine (touch a self-tapping screw). Reading
should be infinite.
5. If either step (3) or step (4) fails, replace the
switch.
ELECTRIC SHOCK can kill.
• Have an electrician install and service
this equipment.
• Turn the input power off at the fuse
box before working on equipment.
• Do not touch electrically hot parts.
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WARNING