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3. Remove the blue jumper lead connected between #1 on
the coil of the main relay and #7 on the coil of the
transfer relay. (The main relay is the upper right relay
when facing the left end of the control box. The transfer
relay is just to the left of the main relay.)
4. Replace the LAF-3 control cover.
5. Set the "POS — NEG" switch (on both the NL Option
and the DC-1500) to correspond to the polarity of the
electrode cable connection.
6. Set the mode switch on the front of the DC-1500 to
"Variable Voltage".
7. Set the toggle switch on the front of the DC-1500 to
"Output Control Remote".
8. Set the DC-1500 welding current as required by the
procedures using the K775 Remote Output Control
shipped with the NL Option.
9. Set the LAF-3 "Inch Speed" control near minimum so
the electrode touches the work lightly before starting the
arc. The NL Option "Inch Speed" control is not in
the circuit.
10. Set the "Hot Start Control" on the NL Option at #2.
This setting does not change the open circuit voltage,
but it will improve starting, particularly at low currents.
Adjust the control for optimum starting.
1. The fan motors have sealed bearings which require no
service.
2. In extremely dusty locations, dirt may clog the air chan-
nels causing the welder to run hot. Blow out the welder
with low pressure air at regular intervals. Also blow dirt
out of the NL Option box.
The "Hot Start Control" does not affect the
starting method of the LAF-3, i.e., "cold" start, "hot"
start, etc. See IM-198-B, Sec. 2.4.9.
11. Set the NL Option "Contactor Drop-Out Delay" switch
to "On". This circuit delays opening of the output con-
tactor for a fixed length of time after wire feeding stops
to prevent sticking.
Follow the same instructions as above except in Step 1,
connect per M13322. Omit Steps 2, 3 and 4. Set the "Inch
Speed" control on the NL Option as low as possible so the
electrode touches the work piece lightly before starting the
arc.
The NL Option kit includes two fuses on the front panel.
The upper fuse (2 amp slow blow) protects the inching cir-
cuit when the option is used with LT-3 and LT-34 wire feed-
ers. The lower fuse (2.8 amp slow blow) protects the 115
volt DC circuit (#1 and #2). If replacing either fuse use the
same size and type.
The DC-1500 has built-in protective thermostats. If the rec-
tifier or transformer reaches the maximum safe operating
temperature because of frequent overload or high room tem-
perature plus overload, the contactor drops out stopping the
welder. The thermostat automatically reset when the tem-
perature reaches a safe operating level. Press the "On" but-
ton to start the welder.
The power rectifiers are also protected by a special solid
state circuit. With the occurrence of a short circuit or ex-
cessively high overloads, the input contactor opens. When
the overload is removed, press the "On" button to start the
welder.
An 8 amp slow blow fuse located on the front of the machine
protects the 115 volt auxiliary AC circuit (#31 and #32)
from overload. If replacing, use the same type and size fuse.
-11-
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