I own both a Millermatic 175 Mig welder for steel work, as well as Lincoln TIG welder for aluminum. I was bitchin’ to my buddy that my TIG skills are poor and I cannot seem to get a consistent weld. He said to get a spoolgun for my MIG and do MIG aluminum. After a bit of looking around I realized that I could get the Miller SpoolMate 100 spool gun for about $220 and with a little re-wiring I would be in business.
CAUTION: these modification will void your warranty. Miller suggest you do not make this modification because if the spoolgun motor shorts, it could fry the drive board. Also you will be working with lethal voltage and current – make sure you know how to drain capacitors before attempting any of this stuff. If you hurt or kill yourself, its your fault.
The only reason why the Millermatic 175 cannot run a spool gun is that there is no drive power going to the gun and no switch to direct the drive power from the main roller to the spool gun.
All this modification does is to direct the drive power to a switch, which then will direct the drive power to either the main drive roller or to the spool gun.
What you will need
- A 1/2″ DPST panel mount switch with 1/4″ blade connectors and a long threaded body
- 6 female insulated 1/4″ blade connectors
- 4 or so feet of 16ga stranded insulated wires
- a foot or so of small heat shrink
- A couple of CPC female pins – available from mouser, digikey, allied, newark – probably even your local electronics shop. Made by AMP, distributed by TE electronics – part number #1-66101-9
- Soldering iron and some electronic solder
- A pair of crimper pliers
- A nut drive set
Get the welder ready
- Unplug the welder
- Remove the cover. Remove all the 1/4″ machine screws. There are 4 bolts on the handle – remove the two closest to the main drive roller.
- Drain the capacitor, use a meter to make sure there is no power in the capacitor
Identify the parts involved
The following picture shows:
- The main drive motor
- The plug which connects the main drive motor to the control board
- The plug that connects to the spool gun
Hole for the swtich
- Mark a location on the front panel for the switch – make sure there is nothing behind it. I put mine just to the right of the voltage knob.
- Drill a 1/2″ hole in the front panel of the welder
Connect Main Motor wires to Switch
- The motor wires are red and black – and they plug into wires that are both white. Mark the white wire that cooresponds to the black wire so you can match these up later (or else the main motor will run backwards!)
- Clip off the connectors from the drive motor and the wires that run to the board
- Each of these wires will need to reach the switch. If needed you will have to solder extra wire on to these wires to reach the switch.
- Crimp 1/4″ female spade connectors onto these wires.
- Connect the wires to the switch as follows. The motor wires from the board go to the centre lugs of the switch. The wires that go to the main drive motor go to the top lugs on the switch. Make sure to match the black wire of the switch to the wire you marked earlier.
Connect the plug from the spool gun to the switch
- Cut two pieces of wire that will reach from the switch to the spool gun plug.
- Crimp a 1/4″ connector on one end of each wire.
- Crimp a CPC female connector onto the other end of the wires.
- Insert the CPC female connectors into the spool gun plug.
- Connect the 1/4″ connectors to the remaining two lugs on the switch.
- Mount the switch in the hole
[click on picture to enlarge]
- Make sure there are no exposed wires or connections.
- make sure no wires will touch any other parts (like the hot transformers)
- turn the voltage to its minimum position, turn the feed to a medium position
- Flip the switch to the lower position – this will be for the main drive spool
- start the welder, click the trigger and the main driver roller should move forward
- move the swith to the upper position – this will be for the spool gun motor
- start the welder, click the trigger and the spool gun driver roller should move forward
If either roller moves backwards, you need to flip the wires on the switch – make sure to unplug the welder and drain the capcitor before moving the wires.