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B-20
VOLTAGE CONTROL RESPONSE
The LN-9 GMA is provided with selectable voltage con-
trol response. Proper setting depends on the power
source and process being used. Refer to the appropri-
ate power source connection diagram for the proper
connection of the jumpers located on the LN-9 GMA
Voltage Board.
To change the voltage control response:
a) Turn OFF the control power to the LN-9 GMA at the
power source.
b) Remove the screws holding the control section
cover in place and swing open.
c) Position the jumper plugs on the Voltage Board
according to the appropriate power source con-
nection diagram.
d) Reassemble.
STARTING CHARACTERISTICS
SELECT ACCELERATION
The LN-9 GMA models can provide optimum starting
for different processes. The wire feeder is designed
to start with two different speeds of controlled acceler-
ation. As shipped, it is connected for fast acceleration,
which is the best for most open arc procedures.
However, the slower acceleration may be more desir-
able for long stickout applications and most submerged
arc procedures. If the electrode being used does not
give satisfactory starting because of "stubbing" or
"blasting off," slower acceleration can be obtained by
modifying the LN-9 GMA models as follows:
a) Turn OFF the control power to the LN-9 GMA at the
power source.
b) Remove the screws holding the control section
cover in place and swing it open.
c) On machines having an L7253 Control PC board,
move the jumper plug on the PM Control PC board
from pin "F" to pin "S."
On machines having an L10068 Control PC board,
set the DIP switch on the PM Control PC board to
the "S" position.
d) Reassemble.
OPERATION
START VOLTAGE TRIM
The start voltage is the voltage provided by the welding
power source before establishing the welding arc. This
start voltage setting is a function of the open circuit
voltage characteristic of the power source, the SET
value of the weld voltage, and the start voltage trimmer
(R41) setting on the LN-9 Voltage PC Board. As set at
the factory, the start voltage trim level is typically about
20% higher than the LN-9 GMA SET level. This gen-
erally gives good starting for steel cored and MIG
processes using CO
gas. If you are using "hotter" gases (such as
Argon/Oxygen blends) and other processes (such as
stainless steel MIG), arc flaring may occur at start,
which requires lowering the start voltage trim as fol-
lows:
a) Turn off the control power to the LN-9 GMA at the
power source.
b) Remove the screws holding the control section
cover in place and swing it open.
c) On the voltage board, locate trimmer R41 (below
R40 next to the 1/8 amp fuse) and labeled START.
d) The slot on the START trimmer is marked with a
red seal for factory setting. To decrease the facto-
ry setting, turn the slot CCW (opposite to the
labeled arrow direction).
NOTE: If the start trim is set too low, stubbing may
occur at start, requiring increasing the START
trimmer by turning the slot CW (in the direc-
tion of the labeled arrow).
e) Re-assemble.
RUN-IN FEATURE
On new machines (above code 10350) a "Run-in" trim-
mer, labeled "RUN-IN," is provided on the new L10068-
1 Control PC board.
This trimmer can be used to set the run-in wire feed
speed as a percentage of the weld speed. When the
trimmer is turned fully counterclockwise, the run-in
speed is about 5% of the weld speed. When the trim-
mer is turned fully clockwise, the run-in speed is equal
to the weld speed. To increase the run-in speed, turn
the trimmer clockwise; and to decrease the run-in
speed, turn the trimmer counterclockwise.
The factory setting of the run-in trimmer is about 20%.
The trimmer should be set lower if arc starting tends to
stub or blast, and it should be set higher if the arc tends
to flare up. When the Actual button is pressed, the
actual speed setting can be viewed on the digital speed
meter for two seconds after closing the trigger or the
cold inch switch.
LN-9 GMA Wire Feeder
or Argon/CO
blended shielding
2
2
B-20
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