Maintenance; Control Box; Circuit Protection - Lincoln Electric NA-5N Service Manual

D-2

CONTROL BOX

GENERAL
Inspect the control box every 3 months. If
needed, blow dirt out using low pressure air.
No further maintenance should be required.

CIRCUIT PROTECTION

The circuit breaker mounted on the left side
of the control box protects the control circuit
from short circuit conditions and from severe
wire feed overloads. If it is open, determine
and correct the cause for the overload. To
reset the circuit breaker, push in the red
button shown in Figure D.1.
FIGURE D.1 – CIRCUIT BREAKER
RESET BUTTON

MAINTENANCE

RESET BUTTON.
CIRCUIT
BREAKER
If a complete or partial short occurs in the
field circuit, or if there is a defect on the PC
board, a 1/2 amp slow-blow type fuse will
blow. This field circuit fuse is mounted on the
power PC board, shown in Figure D.2, inside
the control box. Before replacing the fuse,
check the motor field for a short condition.
Normal resistance is approximately 700
ohms.
With NA-5 controls above Code 8300, the
field circuit fuse may blow due to frequent
motor field reversals from application
problems affecting the "cold" starting circuit,
such as the power source output being too
low to establish an arc or the welding
procedure causing frequent electrode-to-
puddle shorting. (Refer to Automatic
Shutdown
Instructions.)
FIGURE D.2 – POWER PC BOARD
FUSE LOCATIONS.
NA-5 POWER
POWER
1/2 AMP
SLOW-BLOW
FUSE
The power supply for the electronic circuitry
is protected by a 1/2 amp slow-blow type fuse
shown in Figure D.2. It is located on the
power PC board inside the control box.
NA-5
in Section B, Operating
FIELD
1/2 AMP
SLOW-BLOW
FUSE
D-2