Lincoln Electric IDEALARC IM420-D - Manual (Page 16)

D-1 MAINTENANCE D-1
The control board is designed with adequate protec-
tion so that no damage will occur if the remote control
leads are shorted together or are grounded to the
case. The machine will automatically shut down if
such faults do occur.
An 8-amp fuse located on the machine control panel
protects the 115 volt auxiliary AC circuit (#31 and #32)
from overload. If replacing, use the same type and
size fuse.
IDEALARC® DC-1000
SAFETY PRECAUTIONS
ELECTRIC SHOCK can kill.
• O n l y q u a l i f i e d p e r s o n n e l s h o u l d
perform this installation.
• T u r n t h e i n p u t p o w e r O F F a t t h e
disconnect switch or fuse box before
working on this equipment.
• Do not touch electrically hot parts.
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GENERAL MAINTENANCE
1. The fan motors have sealed bearings which
require no service.
2. In extremely dusty locations, dirt may clog the air
channels causing the welder to run hot. Blow out
the welder with low pressure air at regular inter-
vals as required to eliminate excessive dirt and
dust buildup on internal parts.
OVERLOAD PROTECTION
The power source is thermostatically protected with
two proximity thermostats against overload or insuffi-
cient cooling. One thermostat is located on the trans-
former secondary Negative Output Lead, and the
other thermostat is located on the choke coil. The
thermostats are connected in series in the machine
control circuit so that if an excessive overload is
applied to the machine, or the machine should receive
insufficient cooling on either the main transformer,
SCR bridge assembly or choke, the input contactor
would open and remain open until the machine cools.
It can then be manually restarted by operating the
start push button.
The power source is also protected against heavy
overloads on the SCR bridge assembly through an
electronic protection circuit. This circuit senses an
overload on the power source and opens the input
contactor should the overload remain for a predeter-
mined time. The predetermined time varies with the
amount of overload; the greater the overload, the
shorter the time. The input contactor will remain open
until the power source is manually started with the
start push button.
WARNING