Lincoln Electric IM818 manual Section E, Troubleshooting

SECTION E

TROUBLESHOOTING

Regardless of which torch or feeder used, all MK Products push-pull guns operate on the same principle. The 115 VAC or 42VAC 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 24 VDC torch motor is controlled by a solid state speed control and a pot located in the torch. The torch motor, potentiometer, and micro switch are connected to the cabinet/control box 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.

With the increased torque rating in the current Prince XL motor, P/N 211- 0071, it now draws about twice as much current on start-up as the original Prince motors P/N’s 211-0054 & 211-0056. Even though the duration of start-up is very short, about 15msec, it is too much for the standard 2A fuse to handle. For this reason, all 2A fuses in the motor circuitry (F1) should be changed to a 3AG 4A fast blow 250V fuse, P/N 151-0043. This new 4A fuse is suffi cient for use on all model welding guns on the wire feeders, while still providing protection for the circuitry from any shorts in the motor or motor leads.

This fuse change includes all Cobramatic, Cobramatic II and CobraMig 250/ 260, WC-1, Torpedo’s, and any other motor circuits powering Prince XL or Spool Guns using motor P/N 211-0071.

Remember the micro switch in the torch activates both the 115 VAC or 42 VAC and 24 VDC circuits in the cabinet. Therefore, if the slave motor and brake solonoid operate, but the torch does not, look more toward the 24 VDC circuits, speed control, control cable, or the torch motor. If nothing operates, look more toward the 115 VAC or 42 VAC input, micro switch leads, or micro switch.

The complete pot assembly is connected to the motor and set into the handles. If the pot is disassembled, the pot knob can be put on the shaft in any position and secured with the set screw. Turn the knob fully CCW, then fully CW, then fully CCW again. This will self-align the pot, i.e., fully CCW will be minimum wire feed speed, and fully CW will be maximum wire speed.

Prince XL® - Owner's Manual - Page 14