Lincoln LN-7 - Manual (Page 13)

The Lincoln Electric Company
Cleveland, Ohio 44117 Operating Instructions
SEC J3 OPERATING INSTRUCTIONS
Sec. J3.1.1
Adjusting Current and the Voltage
Use only constant voltage type power sources. If using a
multiple process power source, be sure it is set for constant
voltage output per instructions in the manual for the power
source.
Set the voltage using the controls on the power source.
For the most accurate arc volt^e readings, connect the
meter leads between the work and the brass gun cable con­
nection block of the LN-7 and read the voltmeter while
welding. Approximate welding voltages can be obtained by
reading the power source voltmeter while welding.
On constant wire feed speed type wire feeders like the
LN-7, welding current is controlled by the wire feed speed.
With the ‘Wire Feed Speed’ control set on Min. the wire
feeds at a little under 50” per minute and the welding
current is low. When set on Max., the electrode feeds at
more than 500” per minute and the welding current is high.
If the power source is equipped with meters, the welding
current can be read directly on the anuneter while welding.
If the power source has no meters and the relationship
between current and wire feed speed is known, current can
be accurately set by measuring the wire feed speed. To
measure wire feed speed disconnect the electrode cable at
the power source:
1. Press the gun trigger and feed electrode for 15 seconds.
2. Measure the wire feed in inches and multiply by 4. This
gives the wire feed speed in inches/minute.
3. Adjust the ‘Wire Feed Speed’ control until the desired
speed is obtained.
January 1976
Sec. J3.1.2
Arc Starting
The LN-7 starts at a slow wire feed speed and low cur­
rent and automatically accelerates quickly to the welding
speed set by the ‘Wire Feed Speed’ control. The electrode
should be lightly touching the work when the gun trigger is
pressed. This low starting current improves the starting
characteristics and minimizes skipping, stubbing, and spat­
ter when striking the arc with both normal and Line-Fill
long stickout welding procedures. This standard feature
requires no adjustment.
September 1976
Sec. J3.1.3
Circuit Protection
The AC input line is protected by both a circuit breaker
and a fuse.
The circuit breaker protects the LN-7 from moderate
overloads, usually caused by excessive wire drag or other
wire feeding problems. To reset the circuit breaker, push
the red button on the underside of the control box. If it
opens again, determine the cause of the overload.
The fuse protects the LN-7 from sudden high current
overloads such as a shorted motor or other short circuit
conditions. Determine and correct the cause of overloading.
Replace the fuse with one of the same size and type.
November 1972
Sec. J3.1.4
Adjustable Wire Reel Brake
The mount for standard 50 and 60 pound electrode coils
includes a two position brake assembly. Generally the
brake should be at the inner position (nearest to the wire
reel shaft) for wire feed speeds below 400”/min. It should
be at the outer position for the faster wire speeds often
used when feeding small diameter electrode.
To adjust the brake position, remove the wire reel. Pull
the cotter pin that holds the brake shoe to the arm, move
the shoe and replace the cotter pin. Do not bend the cotter
pin — it is held in place by a friction fit.
Machines built before November 1972 do not have an
adjustable brake.
See Sec. J3.1.6 for adjustment instmetions for the brake
on the spindle for 10-25 pound spools.
November 1972
Sec. J3.1.5
Wire Reel Loading — 50 and 60 Pound Coils
1. To remove the wire reel from its shaft, grasp the spring
loaded knob and pull it out. This straightens the knob so
it seats into the shaft when released. Remove the reel.
2. Lay the reel flat on the floor, loosen the spinner nut and
remove the cover plate.
3. Before cutting the tie wires place the coil of electrode on
the reel so it unwinds as the reel rotates clockwise.
A. Be sure the coil is placed so the spring loaded arms
will not interfere with the later removal of the coil tie
wires. (See photo.)
B. When loading .035 and .045” electrode, be certain
the coil is placed on the reel so the spring loaded arms
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