MK Products Cobramatic II - Manual (Page 18)

Cobramatic ® II Owner's Manual - Page 11
S
ECTION
E T
ROUBLE
S
HOOTING
Regardless of which torch or feeder used, all MK Products push-pull guns
operate on the same principle. The 115VAC 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 torch 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 spindle is used simply to
keep the wire slightly taut, so it will not pull off the spool while feeding wire.
The 24VDC torch motor is controlled by a solid state speed control and a pot
located in the torch, cabinet or remotely. The torch motor, potentiometer, and
micro switch are connected to the cabinet via a control cable and amphenol.
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 torch activates both the 115VAC and
24V circuits in the cabinet. Therefore, if the slave motor and brake solenoid
operate, but the torch does not, look more toward the 24V circuits, speed
control, control cable, or the torch motor. If nothing operates, look more
toward the 115VAC input, micro switch leads, or micro switch.
The objective of this trouble-shooting section is to identify and replace faulty
assemblies, not individual component repairs.
S
LAVE
M
OTOR
T
ENSION
T
EST
To check for proper operation of the slave motor, the following test may be
performed:
Disconnect welding power from Cobramatic ® II cabinet.
Plug Cabinet into 115VAC power outlet (different for export) and turn cabinet
"ON"
Remove torch wire conduit from the outlet guide on the slave motor assembly.
Cut a piece of .045" hard wire 10" long and make a small loop on one end
to attach the spring scale.
Place the wire size selector switch on the front panel in the .030 & .035
ALUMINUM ONLY position.
Insert the .045" hard wire into slave motor assembly, press trigger, and
tighten slave motor drive roll pressure adjusting nut until the drive roll stalls.
The spring scale should read about 1 1/2 lbs of pull when the slave motor
stalls.
Now repeat the test with the wire selector switch set to the "ALL OTHER
WIRES" position.
Depress the torch trigger and readjust the drive roll pressure adjusting nut
until the drive stalls once again. This time the spring scale should read
approximately 4 1/2 lbs.
T
ROUBLE
S
HOOTING
M
AIN
B
OARD
MAIN BOARD - Test Points
High - 9 to 10 volts
Low - 1 volt or less
A voltmeter is required for the following test. TP3 is ground.
Turn the unit “OFF” and unplug the J9 connector going to the timer board, if
so equipped, from the main board.
Turn unit “ON” and set meter to DC.