Lincoln Electric IM355-C LN-9 GMA Operator's Manual page 31

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If such a grounding lead fault occurs, the meter will still
be on and will be reading. The trigger circuit will not
operate, however. To release the circuit, press the
"GLP Reset" button. See Figure B.3 or B.4 for the
location of this button.
The following precautions are recommended to avoid
GLP shutdown:
• Do not allow the electrode to contact the case of the
wire feeder or uninsulated part of its wire reel stand
when the gun trigger is activated.
• Be sure that all work lead connections to the work
make tight metal-to-metal electrical contact.
• Do not allow excess input cable or work cable to be
placed closer than 3 feet to the wire feeder.
• Do not coil excess input cable assembly or use an
uncoiled assembly as shipped from the factory.
Instead, loop excess length back and forth in 3 to 6
foot straight lengths. Coiling the input cable results in
a transformer action between the electrode conductor
cable and ground lead in the multiconductor cable
and the ground lead in the multiconductor control
cable. This can cause current to flow in the ground
lead, which will falsely activate the GLP.
AUTOMATIC SHUTDOWN
If the LN-9 GMA voltage control is unable to supply the
SET value of arc voltage while welding, the automatic
shutdown circuit will activate. This protection circuit
immediately returns the LN-9 GMA control to idle state
within a few seconds after the arc voltage discrepancy
occurs.
Typical causes for the activation of this protective shut-
down circuit are as follows:
a) SET value of arc voltage is outside the power
source range.
b) Power source voltage control not set for REMOTE.
c) Misconnection of LN-9 control cable leads to
power source.
d) Incorrect weld polarity connections, or settings, at
the LN-9 GMA or the power source.
e) Lost connection of LN-9 GMA voltage sensing
leads (#67 and #21) between the arc and voltage
control, or a blown 1/8 amp fuse on the Voltage PC
board.
OPERATION
In the case of full range control power sources, such as
the DC-600, this protective shutdown circuit could pre-
vent welding under the conditions of (c), (d), and (e)
above by holding the power source output at minimum.
The power source output might even be too low to
establish an arc.
Although out of range shutdown can occur with all
power sources when working with very low or very high
arc voltages, it is most likely to occur when using the
R3S models with somewhat limited voltage range of
the various taps. For instance, if the R3S-400 triangle
tap setting is for 31 volts, the range of control from the
remote circuit is approximately 7 volts, i.e., 27-1/2 to
34-1/2 volts at nominal input voltage. If the LN-9 GMA
controls are set for 29 volts and the input voltage to the
R3S goes up, it may not be possible for the LN-9 GMA
control circuit to hold the 29 volts. The welding will shut
down. By changing to the 27 volt triangle setting, the
range will be approximately 23-1/2 to 30-1/2 volts, and
at high input voltage there will be sufficient control to
hold the SET arc voltage.
The same general procedure can be used on other
power sources. For example, if the LN-9 GMA keeps
shutting down and the other possible causes have
been checked, adjust the SET voltage higher and/or
lower than the desired voltage. Then you can deter-
mine what change in the range controls of the power
source is required to supply the desired voltage.
In some cases, it is also possible to hold the ACTUAL
button pressed while starting the arc. Before the LN-9
GMA shuts down, the actual arc voltage can be read on
the digital meter. Comparing this reading to the SET
reading will tell what change in the range controls of
the power source is required to supply the desired volt-
age. Should the meter read zero, check the connec-
tions of LN-9 GMA sensing leads #21 and #67. Should
the meter read a minus (-) voltage, the polarity con-
nections or settings at the LN-9 GMA or power source
are wrong.
LN-9 GMA and LN-9F GMA Wire Feeder
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