Lincoln Electric COBRAMAX IM774 - Manual (Page 18)

CobraMAX™ Owner's Manual - Page 8
Troubleshooting Guide
Regardless of which gun or feeder used, all MK Products’ push-pull guns
operate on the same principle. The slave motor in the feeder runs at a fast,
constant speed, but has very low torque. It is always trying to feed more wire
than the gun motor wants, and when the motor gets all it wants, it slows the
slave motor, preventing a bird’s nest. Because of the low torque produced by
the slave motor, a brake system is used to prevent wire overrun rather than
tension. The drag adjustment in the feeder is used simply to keep the wire
slightly taut, so it will not pull off the spool while feeding wire.
The high torque 24VDC gun motor is controlled by a solid state speed
control located in the feeder, and a pot located in the gun. The gun motor,
potentiometer, and micro switch are connected to the cabinet/control box via
a control cable and amphenol connector. If this cable becomes damaged, a
variety of symptoms can occur, depending on which wire(s) break. To test,
check each wire for continuity and shorts.
Remember, the micro switch in the gun activates both the slave motor and
gun motor circuits in the cabinet. Therefore, if the slave motor and brake
solenoid operate, but the gun does not, look more toward the gun motor’s
24V circuits, speed control, control cable, or the gun motor. If nothing
operates, look more toward the slave motor’s input, micro switch leads, or
micro switch.
Testing The Gun
Reference the "W" clocked gun wiring diagram on
the CobraMAX™ electrical diagram (in appendix) for information
about pin-outs and locations.
Motor Check
Remove the gun connector from the cabinet.
Using the gun amphenol connector, check the resistance across pins
“A”
and “B” (motor leads). The resistance across the motor should be between
5 - 10 ohms as the potentiometer is turned.
If an open circuit or short exist, check the motor leads and motor
independently.
Testing the Potentiometer - “W” Clocked
Using the gun amphenol connector, check the resistance across pin “D”
(wiper) and pin “C”. The resistance should vary from 0 - 5K ohms as the
potentiometer is turned.
Check the resistance across pin
“D” (wiper) and pin “G”. The resistance
should vary from 5K - 0 ohms as the potentiometer is turned.
Testing the Micro Switch
Using the gun amphenol connector, check for continuity across pins “E” and
“F” when the trigger is pressed.