Maintenance; Control Box; General; Circuit Protection - Lincoln Electric NA-3 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
CIRCUIT
BREAKER
RESET
BUTTON
The field circuit fuse, shown in Figure D.2, is
a 1/2 amp, slo-blo fuse. It is located on the
control PC board and protects the field circuit.
The following conditions could cause this field
circuit fuse to open:

MAINTENANCE

RESET BUTTON.
NA-3 AND NA-4
FIGURE D.2 – CONTROL BOARD FUSE
AND LED LOCATIONS.
POWER
FIELD
SUPPLY
CIRCUIT
FUSE
FUSE
1/2 AMP
1/3 AMP
1D 1C
1/3
AMP
INDICATOR
LED'S
1. Complete or partial wire feed motor field
short. Normal field resistance is
approximately 700 ohms.
2. A welding procedure with a lot of
electrode-to-puddle shorting. This
rapid arc shorting may cause the field
voltage polarity to change frequently
and blow the fuse. (Indicator LEDs 1C
and 1D will both flicker when welding.)
3. Too low of an impedance when idle
across terminals #21 to #67. Condition
may be caused by the following:
a. Something external to the NA
controls and
causing a partial short across
terminals #21 to #67.
b. Use of a non-Lincoln Electric
power source.
c. A defective Lincoln Electric power
source.
4. A defective control board.
The control PC board is located behind the
inner panel door.
D-2
REMOTE
SWITCHES
FUSE
(NEWER
MODELS)
power source