This optional 3-function module permits using the
Migmaster 251 for spot welding, burnback control to
keep wire from sticking at end of weld, and trigger latch-
ing for long weld runs.
Before installing this kit, make sure all primary in-
put power to the power source is disconnected and/
or lock out procedures are in place.
INSTALLATION
1. Remove and discard the upper blank plate from
the control panel of the Migmaster 251 unit. Re-
tain the 4 mounting screws.
2. Remove the top hinged cover and left side panel
from the Migmaster 251 unit and set them aside.
3. Feed the control wires and the U-shape current
detector assembly of the Spot/Burnback module
through the rectangular hole in the control panel,
and then mount the module using the 4 mounting
screws retained from step 1.
4. Route the control wires through the hole marked
1 in the wire feeder compartment and above the
output studs. Restrain them with cable ties.
5. Remove the jumper plug from the upper right re-
ceptacle on the units main control PC board, and
then connect the control wires from the Spot/
Burnback module to this receptacle.
F-15-359
June, 1998
INSTALLATION & OPERATING INSTRUCTIONS
SPOT/BURNBACK/TRIGGER LATCH KIT
P/N 36694
For MIGMASTER 251 PACKAGE
NOTE: Do not discard the jumper plug. If it becomes
necessary to remove the optional module, the
jumper must be reconnected for proper opera-
tion.
6. Locate trim potentiometer R25 near the top center
edge of the main control PC board. This potenti-
ometer is set at a minimum position at the factory
and will not require any adjustments. However, to
adjust burnback time, using a small screwdriver,
rotate R25 trimpot carefully to get a desired
burnback time.
7. Mount the current detector to the work cable near
the negative (-) stud in the wire feeder compart-
ment. To do this, remove nut and reed switch from
the U shape steel piece. Slip the U shape piece
over the cable and then reassemble reed switch
and nut. Tighten nut until snug. Do not overtighten.
8. Reinstall the left side panel and then the top hinged
cover.
OPERATION
Spot Welding
1. Set the Spot/Std/Trigger Latch to SPOT position.
2. Set the Spot timer dial to the desired setting (0.1 to
5.0 seconds).
3. Use a No. 12 Spot Weld nozzle on your torch .
4. Trim welding wire back so that the end is slightly
inside the nozzle.
Be sure this information reaches the operator.
You can get extra copies through your supplier.
2
Install
Current Detector
Install
Spot Module
here.
Hole 1
Torch
Cable
Work
Cable
Figure 1 - Migmaster 251, Feeder Compartment (Right Side View)
Main Control
PC Board
Connect control wires
from Spot Module here.
Hole 1
(Ref.)
Figure 2 - Migmaster 251, Left Side View
R25 trimpot (set to min.)
3
5. Set the Migmaster 251 Voltage and Wire Feed con-
trols to the desired settings. Refer to the Migmaster
251 instruction manual, F-15-357, for other oper-
ating details.
6. Press the torch nozzle squarely on the top plate.
Apply enough pressure to hold the two pieces of
metal firmly together so there is no loose play be-
tween them.
7. Pull the trigger, holding the torch motionless and
firmly. The electrode wire and shielding gas will
be fed to the work, and the arc will be maintained
for the length of time set on the Spot timer of Step
2 above.
8. After the preset time has elapsed, the wire will stop
feeding, the arc will be broken, and the shielding
gas will stop flowing.
A good spotweld will penetrate through both layers
of metal and should have a small nugget on the
reverse side as shown in Fig. 3.
Figure 3. - Cross Section of Good Spotweld
Burnback
The burnback feature provides a time delay at the end
of a weld from the time the torch is released until the
main contactor is deenergized. This delay allows the
welding wire to burn back so it wont stick in the weld
puddle. The Burnback timer dial controls this delay time
from 0.05 to 0.5 seconds.
If the welding wire tends to stick in the puddle at the
end of a weld, increase the Burnback time. On the
other hand, if the wire burns back into the torch tip,
decrease the Burnback time.
Generally, the required time delay depends on the Wire
Speed setting on the Migmaster 251. The faster the
wire feeds into the weld, the greater the time delay will
be required.
Trigger Latch
When the 3-position switch of the module is in the Trig-
ger Latch position, the torch trigger will latch when cur-
rent is detected. The torch trigger can be released af-
ter obtaining the welding arc for long weld runs. To ter-
minate the arc, press and release the trigger again.
NOTE: If the arc is broken with the trigger latched, the
trigger will unlatch approximately 3 seconds
after loss of current detection.
NOTE: Trigger latch cannot be used with the Spool
Gun.
Figure 4 - Schematic Diagram, Spot/Burnback Module
TO MM 251 PCB1 P4
(SEE F-15-357)
SENSOR PROXIMITY ASSY. (S1) - 34372
PC BOARD ASSY. SEQ. CONTROL (PCB1) 31471
(4) BOARD SUPPORT - 950708
(2) POT LIN 250K 2W (R1, 42) - 599670
(2) KNOB - 13730611
PLATE - 32263GY
SWITCH DPDT 3 POS (S2) - 950458
SWITCH SEAL BLACK - 951474
F-15-359 6/98 1M
Figure 5 - Replacement Parts - Spot/Burnback Module, P/N 36694
/